370 (3)

Samuel Morse, 1832

Samuel Morse was absolutely correct, although there is a slight technical issue in the form of propagation delay. Also, we must assume that he meant information, rather than intelligence. That said, there is great value in communicating information instantaneously by sending messages. Also, and it would not have occurred to him at the time, there is great value in storing and later forwarding certain messages. Electronic messaging systems comprise facsimile, voice processing, electronic mail, instant messaging, and short message service. Each system deals with information in a different native form, and each serves its own unique purpose to great advantage. While these technologies differ greatly in their basic characteristics and certainly in their applications, they do share some commonalities. They all reside on computer platforms of various descriptions, and they all yield the greatest benefits when widely networked. Perhaps most importantly, all of these electronic messaging systems are characterized by their abilities to support store-and-forward communications. In other words, a system can accept a message and store it in temporary memory in a mailbox from which it can be delivered or retrieved at a later time. The user often can access the mailbox remotely and may be able to forward the message to another user, perhaps with annotations. Several other of these technologies support instant, or more correctly near-real-time, message communications.

While all of these messaging devices initially were of a proprietary nature, contemporary systems are computer-based messaging systems that generally are networked and are based on standards that ensure both their interconnectivity and their interoperability at some minimal level. You variously can access them from a telephone, computer workstation, or even a cellular phone or other mobile device. Additionally, you often can access them remotely across a WAN through a Key Telephone System (KTS), Private Branch eXchange (PBX), Automatic Call Distributor (ACD), Central exchange (Centrex), or Central Office (CO) system. They also increasingly are enhanced through the application of Computer Telephony (CT) technology; in fact, voice processing inherently is CT. Taken to the technically feasible extreme, CT enables the user to access a variety and combination of messages through the switch from a Wireless Local Area Network (WLAN)–attached, multimedia tablet PC workstation using a single, intuitive Graphical User Interface (GUI). Finally, the separate technologies of facsimile, voice processing, e-mail, and instant messaging currently integrate to yield unified messaging systems which allow voice, audio, text, facsimile, image, and even video messages to blend, thereby enhancing the aggregate effectiveness and impact of the individual messages. The technology currently exists to support unified messaging, and a number of such systems are commercially available, although they have been slow to penetrate the market. The next step in the evolution of messaging systems is that of unified communications, which will support the translation of message formats in such a way that an end user can receive any message or combination of messages in virtually any native message format using virtually any device (e.g., cellular telephone or computer), with the formats translated for optimum display or presentation. Further, the end user can respond to that message with the translations working in reverse.

4.1 FACSIMILE (FAX) SYSTEMS

Lee Hills and Timothy J. Sullivan, Facsimile, McGraw-Hill Book Company, 1949

Facsimile comes from the Latin facere simile, which translates to make similar. Traditional facsimile systems are unique as they communicate information in graphic form, rather than audio or data form. Edward Davy invented the first practical facsimile machine in 1837 but abandoned the invention shortly thereafter. Alexander Bain (1811–1877), a Scottish clockmaker and inventor, revived the concept and patented the recording telegraph in 1843. Bain's primitive transmitting device used a stylus attached to a clock pendulum that passed over metal type, sensing dark and light spots on a metal-plated document. The dark spots were transmitted via electrical signals over a telegraph circuit to a synchronized clock pendulum on the receiving device, which passed over chemically treated paper, making a dark stain at a corresponding point where the transmitter sensed a dark spot. The Bain device was used commercially in the United States and England, where it competed with the Cooke–Wheatstone telegraph, which could transmit images through etching metal with a stylus. The first commercial facsimile service was established in 1865 by Giovanni Casselli with a circuit between Paris and Lyon. Circuits were added to other cities, and Casselli sent 5000 faxes in the first year using his patented Pantele-graph machine, which was based on the Bain recording telegraph. The service was discontinued in 1870. A number of other inventors developed various wireline facsimile devices over the next 50 years or so, but none achieved any great level of success, for they were overshadowed by the much more functional and practical electric telegraph (1844). The electrical telegraph system was invented by Samuel F. B. Morse (1791–1872) and Alfred Vail (1807–1859) and began operation in 1844. That system involved a transmitter in the form of a traditional manually operated telegraph key for sending alphanumeric data using Morse code. The receiver recorded the code symbols with an armature that scratched a paper tape. The stock ticker (1870), which was the predecessor of the teletype, and the telephone (1876) further discouraged usage of facsimile systems.

The next wave of facsimile development was in the early 1920s, with work on both wireline systems and Amplitude Modulation (AM) and Frequency Modulation (FM) broadcast radio systems. The Associated Press started a wire photo facsimile service in 1934, stimulating newspapers and law enforcement agencies all over the world to use fax for photo transmission. Although the Radio Corporation of America (RCA) developed a radiophoto system in 1926, it was not until 1936 that 1000 homes in the United States were experimentally equipped with facsimile radio receivers that could print newspapers transmitted overnight, when normal audio broadcasts were off the air. Although commercial developments were stalled by World War II, planning continued and further trials of radio-based facsimile newspaper transmission continued into the early 1950s. Needless to say, this application was impractical and failed miserably.

Facsimile transmission typically involves a pair of stand-alone fax devices that serve to both transmit and receive image documents through built-in modems that interface these inherently digital devices to the analog Public Switched Telephone Network (PSTN). The transmitting fax scans the image document from top to bottom and from left to right, looking for dots of black and white; some systems will also support 256 levels of grayscale and some will support color. Through the modem, these various dots are translated into data bits, the data bits are compressed in order to reduce transmission time, and the resulting compressed data file is translated into modulations of analog sine waves, which travel over a voice-grade analog local loop to the edge of the PSTN. Alternatively, the fax transmission is converted from analog into digital format for transmission over a digital local loop, such as a T1. Within the core of the PSTN, transmission commonly is in digital format. At the egress edge of the PSTN, the process is reversed. The receiving device reads the analog signal through a matching modem and either prints a facsimile of the original document or stores the data in memory for printing or distribution at a later time. The most basic and least expensive fax machines use an old electrothermochemical printing technology that varies the temperature of a print head to cause the image to be reproduced on chemically treated paper. Plain paper fax machines use ink jet or laser printer technology. Early fax machines were expensive and proprietary in nature, which served to discourage their widespread use. Beginning in 1966, various standards initiatives from the Electronic Industries Alliance (EIA) and the ITU-T allowed manufacturers to build to standard sets of specifications, which enabled interoperability of machines, encouraged widespread adoption of the technology, and thereby lowered costs due to greater manufacturing volumes. The generations of fax machines defined by these standards are as follows:

· Group II (G2) fax machines conform to the ITU-T T.3 (1978) black-and-white mode of operation, which accomplishes modest bandwidth compression through the use of encoding and Vestigial SideBand (VSB) transmission. (Note: Vestigial sideband is a technique involving the transmission of the carrier, one complete sideband and only a portion of the other sideband. The VSB assists in demodulation of the signal.) Group II machines use AM and Phase Modulation (PM) at a carrier frequency of 2100 Hz. Group II machines use compression to improve transmission speed to approximately 2–3 min per page, but resolution remains relatively poor at 100 lpi. Group II machines use the same obsolete electrochemical printing process as Group I machines and are, themselves, considered obsolete.

· Group III (G3) fax machines conform to ITU-T Recommendation T.4 (1980) and are backward compatible with Group I and Group II devices. Group III devices convert a document to digital form and employ a run-length encoding algorithm, as described below, that compresses the document prior to transmission.

· Group IV (G4) fax machines conform to ITU-T Recommendations T.563 and T.6. Group IV machines are highly specialized and relatively expensive fax computer systems designed to make use of digital circuits to improve quality and improve transmission speed at rates up to 64 kbps. Circuit options include switched 56 kbps service and Integrated Services Digital Network (ISDN) at 64 kbps. Group IV fax machines also are Group III compatible and connect to analog circuits as required. Group IV machines are unusual, particularly in North America, where ISDN penetration is relatively light. Table 4.1 provides a view of the basic characteristics of each ITU-T fax generation [2–5].

· Standard: 98 × 203 (100 × 200)

· Fine: 196 × 203 (200 × 200)

· Superfine: 392 × 203 (400 × 200)

Resolution clearly has an impact on the size of an image file, as greater resolution involves more lines per inch in scanning and dots per inch in sensing, which increases the number of bits required to express the image in digital terms. As the resolution increases, the number of bits required to express the image increases, and the amount of time required to transmit the set of data increases proportionately, assuming that the available bandwidth is constant. The yield, of course, is more dots per inch in printing, which improves image quality. Compression offers a solution to this bandwidth issue without compromising print quality. There are three forms of compression used in Group III/IV fax systems:

· Modified Read (MR), a Group III option used in some machines, scans and compresses the first line using MH. Subsequent lines are scanned and compared to the first line, and only the differences (deltas) are encoded and transmitted. This process continues for some predetermined number of lines in a group, at which point the process is reset and the first line in another group is encoded using MH, and so on. MR is an optional compression algorithm that is particularly effective if there are few differences between lines.

These computerized approaches have several drawbacks, however. First, the transmitted documents either must exist as computer files or must be scanned by peripheral equipment and converted to computer files through a rastering process accomplished by application software. Second, the receiving fax computers must be turned on and networked continuously in order to be accessible. Third, in a stand-alone PC environment, the process of fax receipt may interrupt other applications in progress at the receiving computer workstation. Finally, the received documents are memory-intensive image files, which must be converted to text files in order to achieve full effectiveness. Also, so many people now have broadband access [e.g., Asymmetric Digital Subscriber Line (ADSL) and cable modems] and so seldom use their modems for dial-up access that PC-based fax is just too troublesome for a large percentage of users.

On the positive side again, the converted documents can be fully editable text files that can be forwarded to other workstations or servers without suffering the loss of quality characteristic of documents refaxed via the traditional approach. You also can archive the converted incoming faxes and burn 100,000 or so onto a single CD-ROM disk without having to scan them first. An additional advantage to this approach is that you can retrieve the faxes over the Internet, thereby relieving the recipient of the requirement to have access to a conventional fax machine.

Fax-On-Demand (FOD) most commonly is an integration of voice processing and facsimile. The traditional FOD approach involves a voice processing front end that answers the telephone call, then prompts the caller to select a document from a menu of options, enter a return fax number, and perhaps enter a credit card number for billing purposes. The system also may have the capability to automatically verify the credit card number on a machine-to-machine basis. FOD has integrated with websites for access over the Internet. Visitors can click a fax back button, select the requested documents, and enter a return fax number and billing information.

FOD systems can be delivered on a turnkey basis, or the user organization can build one with a component toolkit. FOD systems also may include broadcast capabilities which support high-speed outgoing fax transmission to large numbers of receivers through the entry of a distribution list. In larger applications, FOD systems are in the form of fax servers, typically residing on dedicated computer platforms and accessible by multiple client workstations across a LAN.

While e-mail and the Internet currently may be the preferred methods of electronic communications, fax continues to offer advantages as the lowest common denominator, which is particularly significant in developing countries and other circumstances where Internet access to e-mail is not available. Like e-mail and the Internet, FOD is fairly instantaneous. Although typically in black and white, cleverly formatted documents rich in graphic content can be faxed easily and quickly. Further and very much unlike most e-mail systems, fax provides instantaneous reporting of the results of transmissions, whether successfully delivered or not.

Conventional fax is based on a number of international standards, which naturally increased in number and complexity over time and by generation. Those standards include T.30 and T.434.

T.30 is an ITU-T standard (1996) that describes the handshaking protocol used between two Group III/IV devices for establishing and maintaining communications. T.30 also provides for routing faxes to users via subaddresses or fax mailboxes. Message security is included, so that only those responsible for certain manual routing processes can view even the cover page. The routing can be accomplished in several ways, including DTMF, DID, OCR, and manually:

· Dual-Tone MultiFrequency (DTMF) routing requires the sender to enter the appropriate fax extension via a telephone tonepad.

· Optical Character Recognition (OCR) software permits the server to recognize the name or special identification of the intended recipient; OCR currently is more expensive and less reliable than the other options.

· Manual routing is the most common approach, with an individual viewing only the cover page and then routing the fax as appropriate.

In a client/server computing environment, each LAN-connected client workstation is assigned a fax extension number. As the fax server receives inbound fax messages, it automatically routes them to the specific workstation associated with the intended recipient. Through entry of the appropriate security password, the recipient then accesses the facsimile message. Assuming that the message is T.434 compliant, the recipient can edit and annotate it prior to either responding or forwarding the fax to a user-definable distribution list. Software exists that allows the server to recognize the dialed telephone number with the trailing subaddress; the fax then can be routed to a fax machine, another client workstation, or an e-mail address. Further, the server may be intelligent enough to determine whether to send the message via the PSTN or the Internet or another IP-based network as an e-mail attachment [10].

T.434 is an ITU-T industry standard (1999) for Binary File Transfer (BFT) that permits compliant facsimile devices to send any file type, reproducing the original quality at the receiving end. Additionally, the received document is in the form of an editable file, if allowed by the sender. T.434 provides for interoperability among BFT products from disparate manufacturers, allowing data files to be sent much as e-mail messages so that fax-on-demand essentially becomes file-on-demand. Benefits of T.434 include increased throughput and reduced document storage requirements through data compression. Additionally, the specific file attri-butes (e.g., image format as in .eps, .pcx, or .bmp files) are maintained. The standard works with computer-based facsimile systems and Group IV fax machines. The standard allows the linking of fax systems to photocopiers, scanners, e-mail gate-ways, and PCs and invites integration with PBXs and voice mail systems in a unified messaging scenario.

The Internet and emerging special-purpose IP networks are built on the concept of packet switching and the underlying TCP/IP suite for packet data. Without getting too deep into the specifics of packet switching and the TCP/IP suite, which are presented in several subsequent chapters, suffice it to say that the two concepts work together very nicely to support reliable fax transmission over a highly shared packet data network. Packet networks require that a file of data be fragmented into multiple, discrete units, or packets, of data that flow independently over the network from the originating edge to the terminating edge, where they are linked together and where the original file of data is reconstituted. Packets of all sorts flow into, across, and out of a network that may support thousands or even millions of simultaneous transmissions, each in packet form, and all of which contend for limited resources in the form of switches and transmission facilities. Under load, this packet-by-packet contention for limited network resources results in congestion, which imposes variable and unpredictable levels of delay on the individual packets. Contemporary fax machines rely on an internal timing mechanism between the transmitting and receiving terminals. The carefully timed PSTN supports this approach beautifully. Because packet networks violate this timing mechanism, however, the devices simply cannot transmit effectively over such a network.

In order to send a fax document over a packet network (Figure 4.2), the terminal equipment must adapt to the inherent nature of that network. You can typically accomplish this adaptation process through a fax gateway, which serves as a physical gate between the circuit-switched and the packet-switched networks. Just as importantly, the gateway runs gateway protocols that convert from the carefully timed PSTN to the TCP/IP-based packet network. IP-enabled fax devices (e.g., fax machines, PCs, and servers) do not require the services of such a gateway. Relevant IP fax standards include T.37 and T.38.

T.38 is an ITU-T Recommendation (June 1998, Amendment 4 September 2001) for store-and-forward fax via e-mail. Derived from X.25 packet standards, T.38 addresses IP fax transmissions for IP-enabled fax devices and fax gateways, defining the translation of T.30 fax signals and Internet Fax Protocol (IFP) packets. The specific methods for various T.38 implementations include fax relay and fax spoofing. Fax relay, also known as demod/remod, addresses the demodulation of standard analog fax transmissions from originating machines equipped with modems and their remodulation for presentation to a matching destination device. Fax relay depends on a low-latency IP network (i.e., 1s or less) in order that the session between the fax machines does not time out. Fax spoofing is used for fax transmissions over IP networks characterized by longer and less predictable levels of packet latency that could cause the session with the conventional fax machines to time out. Packet transmission over such a network can result in variable latency, or jitter. T.38 compensates for both increased latency and jitter by padding the line with occasional keep-alive packets to keep the session active, rather than allowing it to time out. Thereby, T.38 spoofs, or fools, the receiving device into thinking that the incoming transmission is over a real-time, carefully timed voice network. Delays up to 5s can be tolerated in this manner. T.38 improves on T.37 in a number of ways, including immediate confirmation of receipt.

T.38 provides for two transport protocols, User Datagram Protocol (UDP) and Transmission Control Protocol (TCP). UDP is the faster of the two, but the less reliable, due to the lack of error detection and correction within the network. T.38 overcomes this shortcoming either through redundant transmission of the image data packets, which is inherently inefficient at the network level, or through a Forward Error Correction (FEC) technique, which is inherently inefficient at the device level. TCP includes an error correction mechanism employed at the router level, with the routers typically positioned only at the edges of the network. (Note: Switches, rather than routers, typically are positioned in the core of the network.) Although T.38 strips this process from consideration for the IP fax packets, the level of delay nonetheless is increased; therefore, spoofing techniques are required to maintain fax sessions.

In either case, access to the packet network is on the basis of a local call, which does not carry a per-minute charge in many countries. A number of telcos in the United States and abroad support IP fax, as do some Internet Service Providers (ISPs) and most fax service bureaus. IP fax–capable routers have the ability to transmit a fax over an IP network assuming that the level of delay is acceptable and to default to the more conventional means of transmission over the PSTN when delays are deemed unacceptable [11–14]. Such routers also have the ability to secure the fax document during transmission via the IPsec (IP security) encryption mechanism, thereby providing a substantial level of security over the inherently insecure public Internet. In the absence of a defined relationship between fax routers running matching encryption software, the IP fax user is at risk in transmitting over the Internet. As testimony to issues of IP fax security, I just received an e-mail response from a hotel chain asking me to fax some information. The following cautionary statement appeared at the end of the message: "Please be advised that our fax machines transmit through the internet. [sic] For your protection, please block out any non-essential information such as the last twelve numbers of your credit card account."

Fax capability comes in a variety of forms from simple and inexpensive stand-alone Group III fax machines to integrated devices that combine the capabilities of a fax machine, printer, copier and scanner and culminating in Group IV fax servers with IP networking capabilities. Available features include the following:

· Blocking: If caller ID is available on the fax line, the user can build a list of junk fax numbers to be blocked.

· Broadcasting: Also known as group fax, broadcasting allows the user to program a distribution list of fax telephone numbers intended to receive a given fax. The machine will transmit the document to the target numbers, in sequence.

· Color: Color fax was specified in T.30E. While color lengthens transmissions times considerably and reduces the number of pages that can be stored in memory, it certainly is an aesthetic improvement over black and white. Some fax machines using bubble jet, inkjet, or laser print technology offer color, as well as black-and-white, fax capabilities.

· Distribution List: The user can program distribution lists for fax broadcasting.

· Duplex: Fax servers may be full duplex, supporting simultaneous fax transmission and reception.

· E-Mail Gateway: Fax servers may include an e-mail gateway for direct IP fax transmission.

· Forward: A machine can forward incoming faxes to another machine if the user programs it to do so while the user is away from the office, for example.

· Line Sharing: If the telco offers line sharing, two telephone numbers can coexist on the same line, with one number for the fax machine and another for voice telephones. Distinctive ringing patterns distinguish fax calls from voice calls. The fax machine can be programmed to recognize the fax ringing pattern and to autoanswer those calls.

· Phone Book: The user can build an alphabetical phone book for speed dialing by name rather than speed dial code. The phone book can be imported from or exported to other applications.

· Polling: Polling allows a machine to download fax documents stored in a remote machine, with security provided on the basis of a programmable poll code.

· Queuing: Fax servers queue documents for faxing just as print servers queue documents for printing. Multiple queues can be established with priority-level distinctions.

· Redial: The user can program the fax machine to automatically redial a number if the first attempt encounters a busy or no-answer condition. The machine will make a predetermined number of attempts at predetermined intervals.

· Reporting: Fax machines typically offer reports of incoming and outgoing attempts, including fax number, start time, duration, mode [Error Control Mode (ECM) yes/no], number of pages, and result (e.g., OK, send error, stop pressed, and no answer).

· Resolution: Standard (98 vertical × 203 horizontal dpi), fine (196 × 203 dpi), and superfine (392 × 203 dpi) settings typically are available. Note: Higher resolution improves document quality, but at the expense of transmission time.

· Security: High-end fax machines and servers may require that the target recipient enter a password in order to retrieve a protected fax. Without some form of security mechanism, fax is inherently insecure, as anyone walking by a fax machine has access to the document. Also, correct fax transmission is entirely dependent on the sender's entering the correct telephone number.

· Stamping: The user has the ability to stamp an outgoing fax with a time and date stamp as well as sender name and fax telephone number.

· Speed Dialing: The user can build a fax speed-dial list.

Rather than being totally replaced by e-mail and other forms of messaging technology, facsimile appears to have a long, if not highly prosperous, remaining life. Dependable, inexpensive, standardized, and virtually ubiquitous, fax promises to continue its role as a valuable communications tool. While e-mail offers a number of advantages over fax, it is not universally available in developing countries. It also is worth noting that fax, unlike e-mail, does not present any barriers to communication in languages that involve complex alphabets. Further, facsimile is an inexpensive and highly effective complement to other messaging systems. Fax messages also have long enjoyed the advantage of being recognized as legally admissible in court as, unlike e-mail messages, they cannot easily be modified. (Note: Telex transmissions and telephone records also are considered legally admissible in court, as the trusted carrier guarantees the identity of the sender.) Traditional, stand-alone fax machines continue to grow in number even as e-mail replaces fax as the preferred method of communication for the technically privileged with access to the Internet. As a highly effective, lowest common denominator, traditional fax transmission will survive well into the future.

As costs continue to drop, fax penetration will increase. But outside of developing countries and other situations where Internet access is not available or where fax offers unique legal and other advantages, fax usage will continue to decrease. IP fax will grow, but not at the significant rate predicted several years ago. In the face of competition of e-mail over the very same IP networks, IP fax just does not do well. FOD usage also will continue to decrease in the face of increasingly intense competition from e-mail and the Internet and the Web.

4.2 VOICE PROCESSING SYSTEMS

Press one for sales. Press two in a hopeless effort to get technical support. Press three for answers to questions you don't have. Press four if you're gullible and pessimistic. Press five if you're willing to buy something just so you can talk to a human being.

The comic strip Dilbert by Scott Adams

In any event, the Gordon Matthews story is that he was on a business trip in the 1970s and was having trouble reaching his office at Action Communications, the second company he founded. He was having time zone problems and playing telephone tag while trying to pick up his messages. He mentioned the problem to his wife, who suggested that he invent a computer so that he and his employees could leave messages for each other. Matthews went to work on the project, left Action Communications, and founded VMX (Voice Message eXpress) in Dallas, Texas (United States) in 1979. In 1992, Matthews retired and sold VMX to Octel. (Note: Octel subsequently merged with the Enterprise Networks Group of Lucent Technologies, an AT&T spin-off. VMX and Octel systems are now a product line of Avaya, a Lucent spin-off.) Shortly thereafter, 3M bought the first commercial system, a stand-alone voice mail system with an interface to the PBX, from which the call was forwarded in the event of a busy or no-answer condition at the user station. Gordon Matthews' wife, Monika, recorded the first greeting on this first commercial system. Since that time, a great number of manufacturers have entered the voice processing business, changing the nature of the systems considerably to include increased feature content, integrated messaging, PC platforms, application development toolkits, and networking [15, 16].

A default or customized voice greeting provides the calling party with menu options that are exercised through either DTMF (i.e., touchtone) selection or speech recognition with the latter option having become commonplace. The audio input can be either analog or digital, depending on the nature of the connecting circuit. The voice processing system digitizes the signal, as required, and compresses the voice data, generally employing a proprietary code format and compression scheme.

The voice processor interfaces to a KTS, PBX, ACD, or CO and may perform a number of functions. The voice processing system can act as an automated attendant, in which case the switch answers the call and forwards it to the voice processor, which enables the caller to directly access a department or station through interaction with a menu of options on the basis of touchtone or speech input. In the event that the caller does not know the desired station number, an automated directory can provide that information on the basis of a name search. Once the station number is identified, the voice processor signals the switch, instructing it to connect the call. In a voice mail application, the switch directs the caller to the voice processing system in the event of a busy or no-answer condition at the target station. Interfaces to general-purpose computer systems also are becoming commonplace. In such an application, the system provides access to a database such as bank accounts or perhaps an e-mail mailbox, with the data being converted from text to synthesized speech.

Platforms for voice processing no longer are limited to proprietary hardware, except in cases of larger systems for intensive applications. Many smaller organizations and those with certain, specific applications currently make use of special software and voice cards (printed circuit boards) that reside on PC platforms in a client/server environment. A number of manufacturers offer client/server application software suites that include an automated attendant, voice mail, customized mailboxes, and audiotex. Such an approach is highly functional and cost effective, although concerns remain relative to reliability and database integrity and fault-tolerant platforms and security mechanisms go a long way toward addressing those concerns. Additionally, a voice message requires substantial amounts of memory, even when highly compressed [17].

The applications for voice processing have increased dramatically, with penetration having reached the point that it is virtually ubiquitous. Typical applications fall into the categories of audiotex, voice mail, call processing, and Interactive Voice Response (IVR).

Voice mail, the most common application, involves the direction of the incoming call to a voice mailbox associated with a particular user or application. Voice mail digitizes, compresses, and stores the voice incoming message in the mailbox and then advises the user of the fact that a message is waiting, most commonly through message-waiting lamp indication or stuttered dial tone. When the user accesses the system and enters the proper command and password, the message is resynthesized and played back, ultimately in analog audio form in order to be compatible with the human ear. Features may include the following:

· Annotation: A recipient can annotate a message to add a comment before archiving it or forwarding it to another station.

· Archiving: Messages can be archived, or saved, perhaps for a limited amount of time unless they are resaved. Messages may be archived on an external storage medium for legal reasons. As examples, telephone companies sometimes must archive messages for long periods of time when effecting a change of carrier, as must stockbrokers when confirming a solicited trade, and telemar-keters when confirming a solicited sale of certain types.

· Attendant Access: The system provides the caller with the ability to reach an attendant or alternative answering point if the caller does not wish to leave a message. This important feature, if turned on, allows the caller to speak to a real, live person, rather than being trapped in voice mail jail.

· Broadcasting: An authorized user can broadcast a message to a user-definable distribution list. The targeted user must listen to the message in its entirety before playing any other message. This feature can be used to make important announcements.

· Certification: An authorized user can request a certification or confirmation, which will generate a notification that a message has been read by the target system user.

· Class of Service (CoS): The system administrator can define multiple classes of service, each of which provides a different level of privilege for features such as incoming message length, archival storage capacity, broadcasting, and privacy.

· Find Me: The system provides the caller with a find-me locator option. If invoked, the system will try several (perhaps three) preprogrammed find-me numbers (e.g., home office phone, cell phone, and home phone) in sequence. If the system is unable to find the target user, it will so advise the caller and offer the opportunity to leave a message.

· Forwarding: A recipient can forward a message to another system user. E-mail forwarding allows the system to forward a voice message as an audio attachment to an e-mail, with the e-mail address being user definable.

· Off-Site Notification: The system will dial a user-definable outside telephone number (e.g., cell phone or home phone) to advise of a message waiting.

· Personalized Greeting: A user can record personalized greetings, perhaps for specific situations such as a busy condition or a no-answer condition.

· Privacy: A sender can mark a message private or confidential, thereby denying the recipient of the ability to forward it to another user.

· Purge: The system will automatically purge archived messages after a predetermined period of time established by the system administrator. Prior to doing so, the system will leave the affected user a voice message, offering the user the opportunity to resave those messages to avoid their being purged.

In addition to what might be described as more legitimate applications, increased use of voice mail advertising has recently developed. Solicitors have built voice mail databases that enable them to broadcast advertisements and various other messages to thousands of current and potential customers and contributors. While such use is aggravating to many voice mail recipients, recipients do have the option of calling the advertisers and requesting that they remove their names from such a database. Taking voice mail advertising a step further, some service bureau voice mail providers offer discounted or even free service to customers willing to listen to advertising messages each time they access the system. A more legitimate and common application is for school districts to notify parents of their children's absence from school, notify parents that report cards have been mailed via the postal service, schedule sporting events and practice sessions, or announce school closings or delays due to inclement weather.

Call processing applications position the voice processing system as a front-end call processor to a PBX or ACD. The automated attendant feature of the system will answer the call and provide menu options that can be invoked through either DTMF input or speech recognition software. Features may include automated call routing, Automatic Number Identification (ANI), and Fax-On-Demand (FOD) access. Once the caller selects a menu option, the call can be directed to the appropriate agent, extension, or computer resource. Should the system be unable to connect the call immediately, either the call can be placed in queue or the caller can leave a call-back message in a general system mailbox, rather than simply abandoning the call.

United Airlines, for example, provides toll-free access to its reservation centers. Mileage Plus members are provided with different numbers than the general public, and those numbers are sensitive to the caller's Mileage Plus level (e.g., Premier, Premier Executive, and Premier Executive 1K). Through the use of DNIS (Dialed Number Identification Service), callers are segregated by level and directed by the ACD to the logical partition customized for their use. The voice processor then prompts the caller to select either domestic or international reservations. Finally, the processor places the caller into the proper queue to speak to an appropriately skilled agent.

In a database access application, the voice processing system is positioned as a front end to a general-purpose computer on which reside appropriate databases (Figure 4.3). As a means of imposing a level of security to the transaction, various means of caller authentication, such as DTMF input of an account number and Personal Identification Number (PIN), can be employed. More unusual and expensive techniques include speech recognition (recognition of voice commands) and voice print matching (verification of the caller's identification by matching the characteristics of the voice input to a stored sample). That information (e.g., bank or credit card account information) then either is played back from prerecorded sound bites or is voice synthesized for the benefit of the caller, yielding what is commonly known as interactive voice response. Access to multiple databases often is provided across a LAN. Features may include speech recognition (i.e., the recognition of speech) and even voice recognition (i.e., the recognition of a specific voice), voice print matching, and Text-To-Speech (TTS) capability. Speech recognition combined with TTS can allow a complete transaction to be accomplished on a voice basis without human intervention. Even should it ultimately be necessary for a human being to get involved, this initial interaction can considerably reduce operator talk time.

My financial institution, for example, provides account information through IVR, with the following hierarchy of menu options:

· For English, press 1 (one)

· Para Español, marque 2 (dos)

· I pressed 1. Although my English might be poor, it is better than my Spanish.

· For information or services on an existing account, press 1

· Open a new account or apply for loans or credit cards, 2

· ATM or branch locations, 3

· Year-end tax information, 4

· Merchant verification of funds, 5

· At any time during this call, you may speak with a specialist by pressing 0

· To return to this menu any time, press *

· I pressed 1.

· For account inquiries, press 1

· To transfer funds, 2

· For Internet banking or bill payment by phone, 3

· To order checks, 4

· For account maintenance, 5

· To speak to a specialist, press 0

· I pressed 1.

· For deposits, press 1

· Checks, 2

· All account activity, 3

· I pressed 1.

· Using the touchtone keypad, please enter your 15-digit account number followed by the star (*).

· I entered my account number and pressed the star.

· Using the touchtone keypad, please enter your four-digit password.

· I entered my password. Sadly, there have been no deposits made to my account.

The future of voice processing is very bright, indeed. While such systems initially were a North American phenomenon, they now are commonplace around the world. Specific technology futures include archival applications, multimedia/unified messaging, voice-to-text, voice-to-fax, and language translation.

Voice-to-text and voice-to-fax technologies have been developed that will convert voice messages to text or fax messages, and vice versa. While the technology is still maturing at this time, a number of commercially available products will convert text to speech for applications such as remote e-mail and fax access from a telephone.

Speech recognition software enables the caller to speak commands to the voice processing system, rather than entering commands via the telephone tonepad. Such systems are speaker independent, although the speaker must speak clearly and the network connection must be relatively free of noise. While all but the most expensive systems currently are limited in vocabulary, such technology will become increasingly affordable and, therefore, prevalent in the foreseeable future. For example, some years ago IBM developed speech recognition technology to the point that computer system vocabularies exceed 50,000 words [20, 21]. Regardless of the level of sophistication, many users find the current technology too slow and cumbersome and the application annoying.

Language translation systems ultimately will find their way into voice processing systems. Some years ago, AT&T and other IntereXchange Carriers (IXCs) had rather complete plans to implement this developing technology as a replacement for the human translators who currently provide such services. It is just a matter of time until the technology progresses to the point that it becomes sufficiently advanced and affordable to be implemented on a wide scale.

Voice processing systems are destined to become even more commonplace, to the chagrin of the many who bemoan the fact that they no longer can talk to a live human being. While users often hide behind voice mail in order to be more productive in the workplace, callers understandably get frustrated at their inability to reach them. Additionally, many systems are set up intentionally to defeat the caller's attempts to reach any live person—this phenomenon is known as voice mail jail, and callers do not appreciate it.

4.3 ELECTRONIC MAIL (E-MAIL)

Amazingly, 70 percent of all first-class mail in the United States is generated by computers. Much of this is destined for other computers. It is printed, split into separate sheets, fed into envelopes, sent to a mail room, stamped, carried manually to a post office, sorted, delivered to planes and sent to another post office, sorted again, delivered to a mail room, sorted, distributed, and then laboriously keyed for entry into another computer. All of this ought to take place electronically.

James Martin, Telematic Society, Prentice-Hall, Inc., 1981

Federal Express (1971) and other overnight courier services have since become a routine means of sending written documents. Fax machines became affordable and popular in the 1980s, enabling instantaneous transmission of image documents of any sort, not just those text based. Then came electronic mail (e-mail or email), an application software system originally intended for textual messaging. E-mail now permits the attachment of other forms of information, including binary files, images, graphics, and even digitized voice and video. Nonetheless, its primary use remains for textual messaging, at least for the time being.

E-mail has it origins in the mid-1960s as a means for multiple users of time-share computer systems to communicate. E-mail quickly became popular for government and military communications in the late 1960s and early 1970s, especially as an application on the ARPANET (Advanced Research Projects Agency NETwork), which was the predecessor to the Internet. E-mail was popularized in the late 1970s and early 1980s as part of the office automation concept designed to lead us toward the paperless office, which was about as successful as the personal helicopter. Typically residing on a midrange computer, early systems included IBM PROFS (PRofessional OFfice System), Digital Equipment Corporation DECmail (included in the All-in-One applications suite), and the Wang Office. Network-based e-mail services were available from providers including AT&T Information Systems (AT&T Mail), CompuServe (EasyPlex and InfoPlex), MCI International (MCIMail), and Western Union Business Services (EasyLink). The proliferation of PCs and PC LANs in the 1980s and 1990s stimulated the growth of e-mail, which then became affordable and, therefore, accessible by a much larger community of potential users.

E-mail provides the ability to distribute information to large numbers of people virtually instantaneously and very inexpensively. A 50-page document, for example, can be transmitted coast to coast in approximately 30s by using a high-speed modem and in a fraction of that time by using ADSL, a cable modem, or another broadband access technology. Attach a portfolio of photographic images, an audio file, or even a video clip. The cost of such a transmission is in the range of pennies, rather than dimes or dollars for facsimile, or tens of dollars for overnight delivery via the USPS, Federal Express, or a similar courier service. The dark side of e-mail, however, includes the fact that once you click the mouse the message is sent immediately and may be irretrievable. Gone are the days when you dictated a sensitive letter and let it rest overnight in a desk drawer while emotions cooled so you could reread and edit it in the light of a brighter day. Getting darker, still, e-mail is an easy way for reckless or malicious employees to instantaneously expose company secrets, damage reputations, offend co-workers, spread computer viruses, and otherwise create a host of business, personal, legal, and technical problems [23].

E-mail involves application software that resides on various computer platforms. The contemporary e-mail network generally is in the form of a client/server configu-ration involving a dedicated server to which client workstations gain access for messaging purposes. Clients are the workstations that create, transmit, and receive the messages. A client includes software in the form of a Mail User Agent (MUA) that effects compatibility with the mail server. The server provides message storage and transport through a Mail Transfer Agent (MTA). The server also provides directory services to the client, perhaps in conjunction with another server that performs Internet address lookups and Network Address Translation (NAT). Various clients can be linked to a server through Application Programming Interfaces (APIs), messaging middleware (software that logically sits between client and server), and a driver package. Examples include Microsoft Messaging Application Programming Interface (MAPI) and Apple Computer's Open Collaboration Environment (AOCE). Such APIs permit client applications such as word processing and spreadsheets to communicate with an e-mail server. In other cases, special drivers must access servers running proprietary access protocols.

Although some e-mail networks are closed, these messaging islands are increasingly rare. E-mail servers typically support multiple protocols, with internetworking between disparate e-mail systems adding great value to messaging technologies. Most provide for wide area networking over a backbone, or centralized high-capacity network, in order to provide for both outbound and inbound message communications with the outside world through the Internet. Remote access to the internal e-mail resources generally is provided to employees, vendors, clients, and others within the inner circle.

X.400 is the ITU-T international standard protocol for e-mail message handling and document exchange. Created in 1984 and updated in 1988 and again in 1992, X.400 is compatible with the International Organization for Standardization (ISO) Open Systems Interconnection (OSI) model, functioning at layer 7, the application layer. X.400 is a complex protocol that gained considerable popularity in Europe, largely for in-house implementations. In the United States, the preference developed for the Simple Mail Transfer Protocol (SMTP) of the TCP/IP protocol stack, upon which the Internet is based. While most carriers do not use X.400 in native implementations, they commonly use it as a gateway protocol for X.400-to-SMTP gateways, particularly for international networks. As depicted in Figure 4.5, X.400 acts as a gateway protocol, permitting disparate e-mail systems to interoperate at a minimal level over either packet networks or asynchronous dial-up circuits [24].

Lightweight Directory Access Protocol (LDAP) was developed to simplify the demands of the X.500 DAP. Developed at the University of Michigan in the 1993 time frame and described in the IETF's RFC 1777, LDAP is a lean subset of X.500 that can run over TCP/IP networks. LDAP can run as a stand-alone directory system or can be used as a means of accessing an X.500 directory or other directory. LDAP has been extremely popular and currently is in version LDAPv3, as described in RFC 3377. LDAPv3 supports non-ASCII (American Standard Code for Information Exchange) and non-English characters for international directories and can sort through multiple directories on the basis of a single request. Directories follow the X.500 format, which is a hierarchical tree of entries, each of which consists of a set of attributes, each of which has a name. An LDAP directory request might be to provide all available contact information on all persons in the Mount Vernon, Washington, U.S.A. office of The Context Corporation with the first name of Ray who have an e-mail address. That search of the corporate directory would return complete contact information on Ray Horak (that would be me), including full name, title, division and department, physical mailing address, telephone and fax numbers, and any other information available to be shared with the requestor, based on his or her level of privilege.

Access to Internet-based e-mail is a bit more complex. Such e-mail is stored in a network-based mailbox under the control of a national service provider such as AOL or CompuServe; a Web-based service such as MSN, Netscape, or Yahoo!; or a smaller ISP such as Isomedia, in my case. The larger service providers have hundreds, or even thousands, of POPs (Points Of Presence) that allow my daughter, for example, to access her Gmail from virtually anywhere in the country on the basis of a local call. The POPs are in the form of access routers and servers located variously in telco COs or third-party facilities at strategic locations across the country and, for that matter, across the world. The protocols run in such networks often are proprietary in nature.

Remote access through smaller ISPs is more problematic, although based on standard protocols. Such access commonly is on the basis of a dial-up modem connection over the PSTN, which usually is in the form of long-distance calls involving toll charges if the call is placed from outside the local calling areas served directly by the local or regional ISP. Toll-free calling may be offered at an additional charge. Large numbers of local and regional ISPs have formed nationwide consortia linking the POPs in their respective local calling areas through the Internet. These networks generally use one of two access protocols:

· POP3 (Post Office Protocol version 3) is an IETF standard (RFC 2449) used to retrieve e-mail from a remote server over an IP network. POP3 essentially is a store-and-forward service that runs on both the client workstations and the mail server. Prior to accessing a mailbox at the remote server and downloading all mail to the client, the user can elect either to delete that mail from the server or leave a copy on the server. The second option provides advantages such as checking mail remotely while on the road or from another computer, as the user always can access the same mail later from a home location and personal computer. After downloading that mail in either case, the user can disconnect from the remote server and work with the mail offline. Note that POP3 is involved only when downloading mail from the mailbox. When uploading mail, your access is to an SMTP server, which merely forwards mail after looking up the proper IP addresses on a Domain Name Server (DNS). POP3 is widely deployed.

Connectivity likely will remain an issue for some time. A minimum set of agreements must be reached within the e-mail development community in order to resolve issues including commonality of header fields, end-to-end messaging services (e.g., priority transfer, confirmation notification, and security), addressing schemes, and management standards. Most systems, for example, use Simple Mail Transport Protocol (SMTP), defined by the IETF in RFC 821 to pass e-mail to and through the Internet. Yet each SMTP gateway may deal with addressing schemes in a different way, causing conflicts during the process of message routing. Additionally, each e-mail system places dif-ferent limitations on the size of file attachments, and neither delivery confirmation nor user authentication are supported between such systems through SMTP. Further, binary files typically get converted to text and then converted back to binary files on the receiving end, resulting in a complete loss of formatting.

Notably, SMTP was developed to support the seven-bit ASCII code for simple text. This coding works just fine for relatively simple alphabets (e.g., 26-character English), supporting uppercase and lowercase characters. ASCII also supports numbers 0–9, punctuation marks, and a reasonable set of control characters (e.g., paragraph break and page break). ASCII, however, does not support the rich text formatting (e.g., italics, bold, and color, other than the default black in which this document is printed) supported by most contemporary word processing programs. This seven-bit format also prevents the transmission of eight-bit binary data found in executable files.

Some e-mail systems, such as Microsoft Outlook, also support rich text and HyperText Markup Language (HTML) formatting. Developed for the Web, HTML supports very rich text formatting and embedded graphics. Unfortunately, communication with e-mail clients not supporting rich text or HTML creates considerable formatting incompatibilities.

Multipurpose Internet Mail Extensions (MIME) is an SMTP extension that was developed to overcome SMTP's ASCII-based limitation. MIME standards, as defined in the IETF's RFC 2045, include a number of types and subtypes that support a range of data formats. Those types include the following:

· Text type for textual messages. Subtypes include plain text for seven-bit ASCII and rich text for enhanced text formatting.

· Image type for image files. Subtypes include Graphics Interchange Format (GIF) and Joint Photographic Experts Group (JPEG).

· Audio type for basic audio data at 8 kHz.

· Application type for executable code and any data that do not fit neatly into any of the other types. Subtypes include octet stream for binary data and post-script for PostScript files.

· Message type for encapsulated messages within e-mail. Partial subtype permits a long e-mail message to be fragmented at the transmitter and reassembled at the receiver.

· Multipart type supports the combination of multiple types into a single e-mail message [25].

Proprietary e-mail systems and protocols include cc:Mail (Lotus Development), Lotus Notes (IBM/Lotus), Microsoft Outlook (Microsoft), Eudora (QUALCOMM), and Pegasus (David Harris). Online service providers such as America OnLine, Google, Netscape, and Yahoo also use various proprietary e-mail systems. Through gateway technology, such as is in place on the Internet, unlike mail systems can interoperate, at least at a basic messaging level. Gateway software acts as a protocol translator, or interpreter, converting from one native environment to another. In this manner, Outlook and Lotus Notes software, for example, can pass messages. For instance, several editors, the publisher, and I were able to accomplish much of the editing process for this book via e-mail. From my home office, using a desktop computer running Outlook e-mail software and with Internet access via ADSL through Verizon to Isomedia, a local ISP, I sent the editors electronic Word and PowerPoint drafts as e-mail attach-ments, with absolutely no idea what e-mail program they were running internally. The editing process continued on the road via a laptop running Outlook software, with dial-up Internet access through hotel PBXs in the United States and South Africa. The recipients of this mail were able to respond with edits until the document was deemed satisfactory. Incompatibility was not even an issue, thank goodness. (I had to deal with plenty of other issues.)

E-mail systems offer a growing number of features that commonly include time and date stamping and the ability to read, write, reply, and archive messages. Archived messages can be sorted by criteria such as status, priority, sender, date, size, and subject. A variety of file types (e.g., text, binary, audio, video, and image) and file formats can be attached or appended. Features also can include encryption for additional security, receipt confirmation, automated response, and automated for-warding. The ability to build customized distribution lists enables a user to send a single message to large numbers of user mailboxes with the click of a mouse. The following is a list of typical features:

· Confirmation: The sender can request that the recipient send a receipt to confirm that the message has been received and, perhaps, send another receipt to indicate that the message has been read.

· Folders and Files: Mail received can be organized into user-definable folders and files.

· Formatting: Mail format options include plain text, rich text, and HTML. A number of stationary options may be available. A signature can be affixed to outgoing mail, including perhaps sender name, mailing address, contact numbers, and even a quote. For example, I currently affix the following quote to my e-mail: "Whenever I'm asked what kind of writing is the most lucrative, I have to say ransom notes" (originally stated by literary agent H. N. Swanson, who once represented F. Scott Fitzgerald and Ernest Hemmingway).

· Mailboxes: The Inbox contains all received mail; the Outbox contains all out-bound mail not sent; the Junk mailbox contains all mail designated as junk (i.e., spam), either manually or by message rules; the Sent mailbox contains all sent mail; and the Deleted mailbox contains all mail that has been deleted. Mail read is distinguished from mail unread. Mail can be sorted by priority level, status (read or unread), attachment size, sender, subject, date received, flag status (follow up: yes or no), and even color.

· Recall: While there is no Unsend button, it is possible to recall mail under certain circumstances. Microsoft Office Outlook 2003, for example, supports recall if both the sender and recipient use a Microsoft Exchange Server 2000 (or later) e-mail account. It is not possible to recall a message sent to someone's personal ISP POP3 e-mail account. (Note: Outlook is client software; Exchange Server is the Microsoft messaging and collaboration server. IBM offers Lotus Notes on the client side and Domino on the server side.)

· Search: All mail is searchable by key word.

· Security: Mail can be encrypted through the use of a digital certificate.

3. The mail passes through the Network Interface Card (NIC), which organizes it into Ethernet frames, adds the originating Ethernet address of the client workstation and the destination address of the e-mail server, and places it on the corporate Ethernet LAN.

Finally, in 2003, the U.S. Congress enacted the Controlling the Assault of Non-Solicited Pornography And Marketing (CAN-SPAM) Act to curb spam. As required by the act, the Federal Communications Commission (FCC) adopted rules that prohibit sending unwanted commercial e-mail messages to wireless devices without prior permission. This ban took effect in March 2005 and includes substantial penalties for violations. While there have been notable successes in terms of arrests and prosecutions under the law, many spammers have managed to elude detection and prosecution, in many cases by moving offshore and therefore outside the jurisdiction of U.S. law enforcement. While other countries face the same spam issues, many have not passed laws or otherwise taken strong measures against spammers. Perhaps the best solution, at least in the short term, remains the block sender or junk mail filter feature included in all e-mail programs.

E-mail is a great way to communicate, but it also is a favorite tool of scam artists and fraudsters. A popular scam is the Nigerian Scam or 419 Advance Fee Fraud, named after a relevant section of the Criminal Code of Nigeria, where the scam originated and where most activity still originates. The target receives an unsolicited e-mail indicating something along the lines that some member of a previous government or royal family of Nigeria or some other West African nation (or now Iraq or Saudi Arabia or some other exotic place) has had substantial funds frozen by the current government and cannot access or expatriate those funds. The recipient of the e-mail can help by wiring $ 5000 or so as an advance fee or transfer fee for which the target will receive a much larger sum of money. Sometimes the offer is for the target to accept a cashier's check for $ 100,000 and return $ 75,000 of that via wire transfer but keep the rest as a fee. The $ 100,000 cashier's check is bogus, of course, while the $ 75,000 wire transfer is real. This sort of fraudulent activity has gone on at least since the 1970s through the postal service and via fax machines but is much more prevalent these days due to the widespread reach and ease of use of Internet e-mail.

Trojan horses, viruses, spyware, and other malware (malicious software) are more direct attacks on the host computer system that often are spread through e-mail attachments. They also commonly are spread through contact with websites, often as a result of e-mails that entice the recipient to visit those sites. Countermeasures include firewalls, e-mail filters, antivirus software, and a liberal dose of common sense. Gullibility has no place in cyberspace. Trust no one there.

4.4 INSTANT MESSAGING

Then you suddenly tore the market wide open by offering fantastic bargains, trading the six-year rights for seventh-year and eighth-year. Your computer made such lavish use of Instant Messages to Earth that the Commonwealth defense office had people buzzing around in the middle of the night.

Cordwainer Smith, John Fisher100, Norstrilia, ibooks, 1964

The term instant message was first used in the science fiction classic Norstrilia by Cordwainer Smith, the pen name of Paul Linebarger, at least as best I can determine. In the book, Rod McBan's computer stays up late one night trading stocks on the New Melbourne Exchange on his behalf using instant messages in his recorded voice. The computer makes him enough money to buy Earth. I personally have never owned a computer that made me any money on Instant Messaging (IM), although the bank, my wife, and I do own a little less than an acre of the Earth and my computer does help me in my work. Also, I confess that I do enjoy sending the occasional instant message.

Instant messaging, at least in earthly application, is much like e-mail, but in real time. Instant messaging originated in the 1970s on PLATO, a private online instructional system for schools and universities in the United States [29]. Instant messaging was popularized in 1996 by ICQ, an Israel-based company later acquired by AOL. (Note: Instant Message is a service mark of AOL.) Public Web-based IM ser-vices include AOL's Instant Messenger (AIM) and ICQ, Google's Google Talk, Microsoft's MSN Messenger, and Yahoo! Messenger. A number of stand-alone chat clients that support all of these, as well as IRC, are commercially available. Enter-prise systems include IBM's Lotus Sametime, Microsoft's Live Communications Server (LCS), and Novell GroupWise.

Instant messenging is a client/server application that fundamentally is much like e-mail, with several notable exceptions. The following is a comparison of IM and e-mail characteristics:

· Multimedia: E-mail protocol enhancements (i.e., the MIME extension to SMTP) support multimedia attachments, including text, graphics, image, video, and audio. VoIP coexists with e-mail and other applications on IP networks. Some IM systems now support multimedia attachments as well. Some systems also support VoIP and even videoconferencing.

· Temporal: E-mail is a store-and-forward technology designed to support communication in non–real time. IM communications, however, take place in near real time, in conversational mode, much like an Internet Relay Chat (IRC). IM therefore requires that both correspondents be online at the same time. Some IM systems now support one-way messaging if the recipient is not online. In this mode, the recipient can access the message at a later time, much like an e-mail communication.

· Presence: As IM requires that both parties be online, it is essential that some form of presence mechanism be in place to advertise the status (e.g., available or unavailable) of users. As a non-real-time mode of communication, e-mail is insensitive to presence.

· Standards: Although enterprise-level e-mail application software is proprietary, gateways exist to resolve protocol issues and allow intercommunication between proprietary networks. Also, e-mail is highly standardized at the Internet level through the TCP/IP suite. IM is totally proprietary, although standardization is proposed.

According to research conducted by the Radacati Group in 2005, 85 percent of businesses use IM for either business or personal reasons. The study indicates that there were over 300 million IM users globally in 2004 and that number will grow to nearly 600 million by 2008 [30]. Additional research conducted by the Radicati Group projects that the IM volume will increase from the 2005 level of 13.9 billion per day to 46.5 billion in 2009 [31] (Figure 4.7). Research conducted by analyst Michael Osterman in 2005 indicates that about 90 percent of organizations have some consumer IM operating in their networks and that 25 percent of e-mail users also are IM users [32]. Further Osterman research in March 2005 indicates that more than 50 percent of business organizations are using IM for business purposes, that virtually all organizations eventually will use some form of IM, and that 87 percent of e-mail users will also use IM [30]. There are numerous other studies that offer different statistics based on different methodologies, but all seem to suggest that the IM market is huge and that market penetration is significant and growing rapidly.

(Source: The Radicati Group.)

Figure 4.7: Projected growth in IM sent per day in billions: 2005–2009

IM systems, much like e-mail systems, offer a growing number of features that commonly include time and date stamping and the ability to read, write, reply, and archive messages. A variety of file types (e.g., text, audio, video, and image) and file formats can be attached or appended. The following is a list of typical features:

· Privacy: The user can block presence status to all but those on the contact list.

· Contact List: A contact list can be established and maintained and imported from files, e-mail contact lists, or other LDAP-compliant lists

· Attachments: Files and photos can be attached to instant messages.

· Message History: A history of messages can be maintained and organized by correspondent, in chronological order, by session.

· Multimedia: Voice and video communications may be supported as well as IM textual messaging.

· Conferencing: Some enterprise IM systems will support real-time collaboration, including audio-and videoconferencing and whiteboarding, with digital ink (i.e., handwriting).

· Integration: Enterprise systems feature application integration, offering access from IM to word processing, spreadsheet, graphics, and other applications.

· Polling: IM can include a polling feature that allows authorized users to conduct multiple-choice polls to gauge response to questions of general interest to the universe of IM correspondents or a subset of correspondents in a buddy list, i.e., closed correspondent group.

Instant messaging systems all were developed as proprietary systems without thought to interconnectivity. As the popularity of IM grew, however, it became clear that there were advantages to linking disparate systems, both public and enterprise. Gateways were developed to support protocol conversions and thereby support interconnectivity between systems, if not full-featured networking.

The gateways that will link these systems and others are based on various standards initiatives from the IETF. Those initiatives are as follows:

· IMPP: Instant Messaging and Presence Protocol (IMPP) is an effort to define the protocols necessary to build an IM system, including presence awareness and notification, and that will scale to Internet size. The IMPP group has published the following RFCs: "A Model for Presence and Instant Messaging" (RFC 2778), "Instant Messaging/Presence Protocol Requirements" (RFC 2779), and "Common Profile for Instant Messaging," CPIM (RFC 3860). The CPIM defines common semantics and data formats for IM to facilitate the development of gateways between services.

· SIMPLE: The predominant IM standard, SIMPLE is an extension of SIP (RFC 3261) to the suite of services the IETF refers to as Instant Messaging and Presence (IMP). SIMPLE is compliant with RFC 2779 and the CMIP specification. Microsoft's Live Communications Server and IBM's Lotus Sametime, both enterprise-level systems, are based on SIMPLE. Web-based MSN Messenger and Yahoo! Messenger also are based on SIMPLE.

· XMPP: eXtensible Messaging and Presence Protocol (XMPP), as specified in RFCs 3920–3923, is based on the eXtensible Markup Language (XML) to provide the functionality specified in RFC 2770. XMPP is deployed in the open-source Jabber system for which the initial protocols were originally developed.

While some analysts project that IM will soon eclipse e-mail as the primary mode of business communications, most find those projections unrealistic. IM requires all parties to be online, and it is often intrusive. IM just does not have the depth of support to replace e-mail, but it clearly will have a strong position for many years in a suite of messaging technologies.

4.5 MOBILE MESSAGING: SMS AND MMS

Limitations aside, mobile messaging offers great benefits. The ability to communicate in text mode from virtually anyplace at any time is not only a convenience but also a time saver and even a life saver. Multimode communications only enriches the experience.

Mobile messaging over cellular networks takes the form of Short Message Service (SMS) for text messaging, which has evolved into Multimedia Message Service (MMS) as cellular networks have evolved to offer greater bandwidth and device technologies have evolved to support image and video capture and transmission. SMS and MMS have considerable legitimate business applications and have become so incredibly popular for personal use in the younger (i.e., preteen, teen, and young adult) market to the point that they have assumed the status of a cultural phenomenon. While is more pronounced in Asia and Europe than in the United States, the phenomenon is undeniable. Further, it likely is a permanent communications mode, rather than a passing cultural flirtation with a technological curiosity.

SMS volumes are incredible. In the Philippines, where cell phones outnumber landlines 10: 1, studies show that more than 200 million SMS text messages are sent daily—that works out to roughly 73 billion messages per year [34]. According to the Mobile Data Association (MDA), SMS volume in the United Kingdom grew from 1.1 billion in 1999 to approximately 32.5 billion in 2005 [35]. In the United States, the Cellular Telecommunications and Industry Association (CTIA) estimates that 9.8 billion SMS messages were sent in December 2005 and 81.2 billion in the calendar year 2005 [36]. SMS spam is beginning to be a huge problem, which is hardly a surprise. Although the National Do-Not-Call Registry offers consumer protection against SMS spam in the United States, there are exceptions if the recipient has given prior consent to the caller or has an established business relationship with the caller. In any case, the protection is apparently only theoretical, as SMS spam is increasingly an issue. The carriers actually have a disincentive to control the problem, as SMS messages are an optional service that carries additional charges of as much as US$0.10 per message.

SMS is a store-and-forward messaging technology that generally includes a chat option that operates in near-real-time synchronous mode, much like IM. In fact, many IM systems support mobile communications via interfaces to SMS systems. As SMS messages use the same SMTP as is specified in the TCP/IP suite for e-mail, messaging interconnection issues are relatively modest. Interconnection of cellular networks for SMS applications presents something of a challenge in the United States as there are so many transport protocol variations. Second-generation (2G) network protocols include Time Division Multiple Access (TDMA), GSM and Code Division Multiple Access (CDMA). In every case, and whether the SMS message originates or terminates in a mobile phone, the message travels through a centralized message center, also known as a Short Message Service Center (SMSC). Also in every case, the SMS data are packetized, but in TDMA and GSM networks the data packet transport is over the signaling channel via Signaling System 7 (SS7), while data packet transport in CDMA networks is over the normal data channels. [Note: The SS7 protocol limits the packet size to 140 octets, which translates to 160 ASCII seven-bit characters: 140 × 8 = 1120/7 = 160. Where other coding schemes are employed, the number of characters per packet varies. For example, a double-byte scheme such as that used in support of complex alphabets (e.g., Chinese and Japanese) limits the packet size to 70 characters. Content exceeding this limitation must be fragmented prior to transmission and reconstituted upon reception.] In most countries, GSM is the sole 2 G network standard, so gateway issues are much less significant. All cellular networks are limited in terms of bandwidth, of course, although the newer 2.5 G and 3 G networks are much less so. The user interface is always an issue with mobile devices as display size and keyboard size are naturally limited.

Much of the SMS traffic is as a result of partnerships with public IM providers such as AOL, Google, MSN, and Yahoo!. Through these partnerships, computer users are able to correspond with mobile users on cell networks from their desktop, laptop, and tablet PCs. Mobile users also are able to access Web content on these networks from their mobile devices. Gaming is another popular application.

Multimedia Messaging Service (MMS), the next step in SMS evolution is currently available from many service providers and has been widely available in Japan and select other countries since 2001. MMS allows the cell phone user, for example, to create a text message, add a photo or perhaps a graphic downloaded from the Internet, add a video clip, and add a recorded audio file.

· Unified communications, at least according to my definition, takes unified messaging to a higher level, allowing you to receive messages in any format you choose and to respond in the same way, regardless of the format of the original message. In other words and for example, you will be able to respond to the voice message that was converted to text before being sent to your PDA. You will enter a text response that will be sent via e-mail over a wireless network and converted to voice by your unified communications system. That voice response then will be delivered by phone to the caller or deposited in his voice mailbox unless he now must be reached through his PDA, in which case his unified communications system will recognize that fact, find him, convert the message as appropriate, and deliver the response in text format. This scenario, by the way, is one of many convergence scenarios in which voice and data intertwine over circuit-switched and packet-switched networks that are both wired and wireless, with mobility being a critical driver of the application. Taking the scenario one step further, there technically is no reason that the archives and databases of the multiple devices cannot be synchronized so that the fax that was converted into a voice message sent to a cell phone cannot be saved as a text message in all three formats on one or more servers and one or more devices, along with any annotations. In this fashion, messages can be sent from any device to any device, anywhere, anytime, and one time.

· While such an ideal unified communications system does not exist at the moment, the fundamental technologies do exist and will develop to the point that such a scenario will be practical in the foreseeable future. For that matter, this scenario may well be understated, assuming that compression, display, power, and a variety of other technologies develop to even greater levels than I have assumed here. Video mail, for example, by no means is out of the question. In fact, all of these variations on the theme of unified messaging are available in early versions, which currently are being promoted heavily.

· Several formal standards bodies and industry consortia have begun work on unified messaging. The Electronic Messaging Association (EMA) spent considerable effort in the late 1990s toward the development of a mechanism for passing voice mail between voice processors over the Internet. That effort led to the development of the Voice Profile for Internet Mail (VPIM), which is based on MIME and which was published by the IETF as RFC 2421 in September 1998. The IETF continues that work towards the development of RFC 2421v2 and v3, although at a slow pace. There also was some interest at the IETF in loosening the restrictions of VPIM and making it the voice component of a unified messaging protocol suite, although it appears that little progress has been made in the regard in the last few years.

Chapter 5: Public Switched Telephone Network

The Wonders of the Universe, The Werner Company, 1899

The old networks were designed around basic voice communications, or Plain Old Telephone Service (POTS). While the first telephone networks used transmission lines leased from Western Union, telegraphy was conducted over a separate, preexisting network. Since data, image, and video systems did not exist until many years later, there certainly was no requirement to network them. The characteristics of voice traffic were, and still remain, well known and easily understood. Specifically, voice calls are occasional, short, bidirectional, continuous, stream oriented, and analog in their native form.

Voice calls typically are occasional, because talking on the telephone is not the focus of most people's personal and professional lives. Clearly there are exceptions, such as agents who work in call center environments. Human-to-human voice calls also tend to be short in duration–3–4 min or so, on average. While business calls tend to be short and to the point, purely personal calls are more social in nature and tend to last longer. Additionally, some people tend to express themselves in very concise terms, while others tend to be very wordy. (My late mother, rest her soul, was one of the wordy ones. I am not.)

Initially, these networks were isolated islands of local service. The telephone companies soon interconnected with each other and with the long-distance network, usually under government and regulatory pressure. In the United States, the Bell System avoided providing interconnection, preferring to aggressively acquire the independent telcos and even acquiring a large block of stock in Western Union Telegraph Company, which had entered the telephone business in 1877 and was its chief competitor at the time. Increasingly pressured by the federal government under antitrust laws, Nathan C. Kingsbury, an AT&T vice president, wrote a letter to the U.S. Attorney General in December 1913 to resolve various issues. Known as the Kingsbury Commitment, that letter committed AT&T to dispose of its holdings in Western Union, to purchase no more independent telephone companies without the approval of the Interstate Commerce Commission (ICC), and to make interconnection with the independent telephone companies. Eventually, national standards were established to govern the nature and rules of interconnection. The ITU-T governs standards recommendations at the international level.

Many governments have discovered that they cannot easily fund the capital-intensive upgrades their networks require, and they cannot effectively serve the communications needs of their constituents at reasonable cost. They also have come to recognize that the networks are immensely valuable assets that can be sold to fund various social programs. Therefore, the networks have been liberalized, that is, opened to competition, in many nations. The networks also rapidly are being privatized, either partially, with the government continuing to hold controlling interest for some period of time, or completely. As a result, service has become more universally available around the world, the quality of service has improved, the range of services has increased, and the overall cost to the user has dropped considerably. Note: This is a trend, rather than a universal fact, and progress sometimes is slow.

In the Republic of South Africa (RSA), for example, Telkom South Africa was government owned until May 1997, when 30 percent of the company was sold to the Thintana consortium of SBC Communications (United States) and Telekom Malaysia. Telkom South Africa remained a state-enforced monopoly until 2003, when the search began for a qualified Second Network Operator (SNO). Also in 2003, the company went public and was listed on the Johannesburg and New York stock exchanges in March. The government held competitions for the SNO and actually awarded the licenses a time or two, only to retract them for various political reasons. The SNO licenses were awarded again in early 2006 and SNO Telecommunications prepared to launch services in selected areas of the country. The hope is that SNO will take a more creative approach to its service offerings than it took in the selection of its name.

5.1 NETWORK CHARACTERISTICS

Each type of network can be described in terms of a number of key characteristics that define its basic nature and application. The PSTN, also known as the Global Switched Telephone Network (GSTN), can be characterized as designed for voice communications, primarily on a circuit-switched basis, with full interconnection among individual networks. The network is largely analog at the local loop level, digital at the backbone level, and generally provisioned on a wireline, rather than a wireless, basis.

Note that much Internet traffic travels over the PSTN, at least through the Local Exchange Carrier (LEC) access networks. For example, a great many users access an Internet Service Provider (ISP) over the PSTN through a modem embedded in a desktop or laptop computer. Over an analog local loop, the modem dials the telephone number of the ISP, and the connection is provided through a circuit-switched Central Office (CO) designed for voice communications. The ISP's local loop is in the form of a channelized T1 circuit designed for voice. Should you need a connection to the Internet, it is supported from the ISP to the Internet backbone over an unchannelized T3 leased from the LEC and designed for voice. This traditional method of Internet access is giving way to new technologies such as Digital Subscriber Line (DSL), cable modem, and Wireless Local Loop (WLL) technologies. I discuss these Internet access scenarios and the underlying technologies in detail in later chapters.

Traditional voice networks are largely circuit switched, thereby providing great flex-ibility to the end users and significant economies to the carriers. (Note: While packet-switched networks are rapidly replacing circuit-switched networks in the United States and some other highly developed regions of the world, we will defer that discussion.) Large user organizations that communicate intensively between well-defined physical locations (e.g., headquarters, region, and field locations) often employ dedicated circuits in order to mitigate network costs. Such dedicated circuits generally are leased from the carrier(s), making use of existing PSTN transmission facilities. In relatively rare instances, large end-user organizations deploy their own facilities, often in the form of private microwave, to extend connectivity to areas that the telcos find to be economically unattractive or where telco construction charges would be excessive. Also in rare instances, large end-user organizations purchase or lease from the carrier a set of fiber-optic facilities that can be used to connect the user's locations on a dedicated basis. Such optical fibers are contained within a larger set of facilities originally deployed for the carrier's own use and sold or leased to the user on an as-available basis. As Wavelength Division Multiplexing (WDM) made its appearance, carriers began leasing individual wavelengths, or lambdas, to end-user organizations and other carriers.

The traditional voice network originally was analog in nature. The local loop connection terminating at the residence or small-business premises generally is still analog, with the exception of Integrated Services Digital Network (ISDN), which is digital from end to end, and, very recently, Fiber-To-The-Premises (FTTP). ISDN never achieved any appreciable level of penetration in the United States, although it was widely deployed in many other countries. Large user organizations often have digital access circuits in the form of T-carrier or E-carrier, which may be formatted as leased lines or ISDN.

In 1903, only thirty-nine per cent of the world's telephones could be connected with the Bell System. Today, every telephone served by the Bell System can reach about ninety-two per cent of all the telephones in the world.

Telephone Almanac, American Telephone and Telegraph Company, 1934

Complete interconnection between all local and long-distance and national and regional networks is fundamental to the PSTN. Islands of telephony were interconnected many years ago in order that any subscriber might have the ability to connect to any other, subject to availability of transmission and switching capacity and issues of national or regional security. In other words, any-to-any connectivity is fundamental.

When dialing a telephone number, the user effectively instructs the network to establish a connection between two physical addresses based on a logical address, which is a series of numbers following a specific pattern. Using an example with which I am familiar (it's my company), the following logical addressing convention functions in establishing a connection originating from a physical address in Johannesburg, South Africa, and terminating at another associated with the Context Corporation at 1500A East College Way, Suite 443, Mount Vernon, Washington 98273, United States (and in reverse):

· 0 is the access code for an outside line from behind a PABX. (9 is the access code for an outside line from behind a PBX in the United States.)

· 09 indicates that the call is international. (The international access code for calls originating in the United States is 011.)

· 1 is the country code for the United States. (27 is the country code for South Africa.)

· 360 indicates the area code, or NPA. Specifically, 360 is the geographic area of western Washington surrounding the Greater Seattle metropolitan area. Note: 360 is in Local Access and Transport Area (LATA) 674. (11 indicates a specific area in Johannesburg, Guateng Province, and is akin to an area code.)

· 428 is the Central Office (CO) prefix, which indicates a specific Mount Vernon COE of Verizon, the ILEC. These three digits are associated with an exchange that resides in a wire center, which may house several such exchanges. The exchange also is a rate center, meaning that it is identified by V&H (Vertical and Horizontal) coordinates that are used to calculate the distance between that rate center and another so that rates involving distance-sensitive call rating algorithms can be calculated correctly. (The dialing pattern is similar in South Africa from this point, as local telephone numbers are seven digits.)

· 5747 is the line number, which indicates the port and circuit ID, which is associated with a local loop, which in turn is associated with terminal equipment at the physical address of The Context Corporation.

Through such a series of dialing steps, the logical address of the Context Corporation is translated, in steps and across carrier domains, by several networks in order to route the call to the target telephone system. Changes in the dialing scheme require changes in switch logic (e.g., PBXs and COs) in order that the switches can recognize the legitimacy of the dialing pattern. The Context Corporation also has an 800 number (i.e., IN-WATS, or toll-free, number) that the network translates into 360.428.5747 in order to route domestic calls on a toll-free basis. As the 800 number points to a regular telephone number associated with a multifunctional local loop rather than a separate INWATS line, the number technically is in the form of virtual WATS.

Subsequently, however, common sense prevailed as consumers put pressure on the regulators to reconsider the introduction of new area codes. As a result, LEC requests for number blocks were scrutinized and were rejected if their existing number blocks were considered to be less than fully utilized. Further, the NANC introduced number pooling, whereby multiple carriers are each assigned blocks as small as 1000 numbers within a pool of 10,000 per CO prefix. The FCC also instituted a number reclamation policy to ensure that unused numbers are returned to the pool and a 60 percent utilization threshold, increasing to 75 percent over time, that carriers must meet before getting additional numbers in their service area. As of January 1, 2006, 328 area codes were in service out of a possible 800 available combinations that fit the acceptable numbering convention. Current projections are that the remaining supply of area codes will last until at least 2039 [10]. Similar factors in Europe have pressured the numbering plans in that part of the world as well—hence the expansion of the international dialing convention to 16 digits and the eventual expansion of the NANP to 11 or 12 digits once the supply of existing CO prefixes and area codes is exhausted.

The changes in the NPA have impacted the network to a considerable extent, as all network switches must be reprogrammed to recognize and honor dialing instructions under the new conventions. At least as importantly, NPA changes have significant impacts on end users, who must keep current and prospective customers and other contacts informed of telephone number changes. Among other things, adver-tising, stationery, business cards, and signage must be changed and at considerable cost.

Notably, both area codes and CO prefixes are geographically specific, with the exceptions of 500, 700, 900, and toll-free (e.g., 800, 888, 877, and 866) services. When an existing area code is exhausted and a new one is required, there are two choices. The traditional choice includes a geographical split of an existing area code (e.g., 206 and 360), but this causes considerable disruption. The contemporary choice increasingly is that of an overlay area code, which requires that the caller always dial a 10-digit telephone number, even to place a local call. Neither solution is particularly attractive.

Note, however, that this geographical limitation disappears or at least can be extended with Internet telephony, that is, telephony over the IP-based Internet. As an example, an Internet telephony provider can subscribe to a telephone number in the financial district of Manhattan, New York. The end user can connect to that telephone number from a computer-based IP softphone through the Internet from anyplace in the world. So, a call placed from Dallas, Texas, to the Manhattan telephone number can be connected through the Internet to the subscriber, who may be in a hotel room in Mumbai. The subscriber in Mumbai can call through the Internet, connect to that same number in Manhattan, and place an outgoing call to Dallas, with the Manhattan telephone number appearing on caller ID at the Dallas telephone. Whether the call is incoming or outgoing, the Dallas party has no knowledge of the fact that the other party is anywhere other than Manhattan. This technology may well contribute to shortages of telephone numbers associated with major financial centers such as New York and Hong Kong, for example, and may further enable financial scams and other fraudulent activities.

Note also that in September 2000 the Internet Engineering Task Force (IETF) approved RFC 2916, which documents what is commonly known as ENUM (Elec-tronic NUMber). ENUM bridges the gap between the logical addresses specified in the PSTN by E.164 and the logical addresses specified for IPv4 in RFC 791 and IPv6 in RFC 2460. Clearly, it is important to translate between the addressing schemes in a scenario in which voice calls travel both the PSTN and the Internet or other IP network. Therefore, both E.164 and IP addresses are registered with the ENUM Domain Name Service (DNS), which can be consulted by gateways that interconnect the two disparate networks.

5.3 DOMAINS

Perhaps the most effective means of examining the fundamental nature of the network is to consider it in terms of domains, or spheres of influence. The traditional voice network can be organized into functional, regulatory, and carrier domains.

A telephone instrument, taken by itself, is merely a thing of ingeniously fabricated insulating materials and metal. A telephone instrument, capable of interconnection with other telephone instruments, not only locally but with a nation-wide and international communication system, becomes an agency of human service whose horizons extend beyond those on commonwealth or continent. … So measured, its value is limitless.

Customer Premises Equipment (CPE) is the term for transmit and receive equipment in the voice realm, including voice terminals (telephone sets), key equipment, PBXs, Automatic Call Distributors (ACDs), and peripheral equipment such as answering machines. Historically, the local telephone company owned the entire network, from transmitter to receiver, including all voice CPE, which the end user was required to lease from the telco. Beginning in the United States with the Carterfone decision in 1968, end users were allowed to purchase terminal equipment and connect it to the network as long as it was connected through a properly registered interface device rented from the telephone company. In 1975, the FCC's Part 68 registration program allowed for the manufacturers of foreign (i.e., nontelco) equipment to certify that it would cause no harm to the network, thereby eliminating any need for the interface devices.

Data Terminal Equipment (DTE) is the parallel term in the data realm. As computer equipment historically comprised islands of mainframes and attached terminal and printers confined within a data center, issues of interconnection across public networks were modest until the 1970s. So, DTE historically was owned by the end-user organization. Further, the telcos considered DTE to be too complex and, therefore, had no interest in it. A notable exception, of course, was teletypewriters, which the telco owned and interconnected through telex and TWX networks. There were small numbers of terminals connected to mainframes across separate networks through modems, which were leased to end users by the telcos, but the numbers were so small that the issues of ownership were of relatively little concern. The Carterfone decision applied to this equipment as well, so end users were allowed to purchase and interconnect DTE beginning in the late 1960s.

Historically in the United States, the inside wire was owned by the telco, which had end-to-end responsibility for the network. Under the terms of the Modified Final Judgment (MFJ) in 1984, the responsibility shifted to the customer for all new inside wire. Further, the customer was given the opportunity to take ownership of and assume full responsibility for that already in place. Therefore, the demarc also became the point at which the carrier's responsibility ends and the user's begins. Such responsibilities include installation and management, such as upgrade, maintenance, and security. Many other countries have since followed that same path of deregulation.

Switches are the devices that establish connectivity between circuits through an internal switching matrix. In a traditional PSTN environment, such switches are circuit switches, which include COs, tandem exchanges, access tandem exchanges, and International Gateway Facilities (IGFs). On demand and as available, circuit switches set up such connections between circuits through the establishment of a talk path, or transmission path. The switches set up and maintain those connections and provide the associated bandwidth temporarily, continuously, and exclusively for the duration of the session, or call.

The Local Exchange Carriers (LECs) own Central Offices (COs), also known as Central Office Exchanges (COEs) and just exchanges. COs provide local access services to end users via local loop connections within a relatively small area of geography known as an exchange area, or Carrier Serving Area (CSA). In other words, the CO provides the ability for a subscriber within that neighborhood to connect to another subscriber within that neighborhood by dialing a 7-digit number (NXX-XXXX) in the United States. (Note: Dialing patters can vary in other countries.) In cases where overlay area codes are in place, a 10-digit (NXX-NXX-XXXX) dialing pattern is required. The FCC has since mandated 10-digit dialing for many geographical areas, to put new carriers and users in new overlay area codes on equal footing with incumbents. COs also provide a number of services, such as custom calling features (e.g., call waiting, call transfer, and three-way calling) and Centrex. Also through the CO, a subscriber typically gains access to the LEC metropolitan calling area, which does not involve a long-distance (toll) charge, by dialing a 7-digit number (NXX-XXXX). In some cases zone charges apply for calling, generally between noncontiguous zones, with each zone comprising multiple CSAs. Finally, most subscribers also gain access to the various long-distance networks through the CO, with a domestic long-distance call requiring dialing 1 + a 10-digit number (1 + NXX-NXX-XXXX) in the United States.

Tandem switches are network switches that serve in partnership with lesser switches, linking them together. In other words, tandem switches serve no end users directly; rather, they serve to interconnect lesser switches. At the lowest level, tandem switches serve to link together CO switches over dedicated interoffice trunks. This approach can be used to form a fully interconnected and toll-free metropolitan calling area, for example. There are a number of basic network topologies, including full mesh, full tandem, and a combination tandem and direct trunk plan.

· Full Mesh: If all COs are interconnected through direct trunking in a full-mesh network topology, a large number of trunks and trunk groups are required, as calculated by the formula

where n is the number of nodes to be interconnected. If there are eight nodes, as illustrated in Figure 5.1, the number of trunks required is calculated as

· Full Tandem: A fulltandem configuration is the most efficient in terms of trunking, as it reduces the total number of trunks to eight. However, this approach places a great traffic load on the tandem, which much provide all interconnections between the COs. The tandem also becomes a single point of failure, which may present an unacceptable level of risk to the carrier. Further, the tandem adds some amount of call setup time and propagation delay. This configuration also is a physical and logical star configuration.

· Combination: A combination configuration often is the most reasonable approach, as it strikes a balance between trunking and switching. Adjacent COs interconnect directly; nonadjacent COs connect through the tandem. If there is a failure at the tandem level, nonadjacent COs can interconnect via alternate paths under the direction of a centralized signaling and control system.

Depending on the design philosophy of the service provider and the size of the network, there may be as many as four levels of tandem switches in the backbone of the circuit-switched PSTN. At each level, the tandem switches serve to interconnect lesser network switches. Contemporary network switches often are multifunctional, with one physical Class 4/5 hybrid switch partitioned to serve both as a Class 4 tandem and a Class 5 CO.

Access tandem switches serve to connect the LECs (telcos) to the IXCs (long-distance carriers) over dedicated interoffice trunks, known as access trunks. In this manner, the local service providers originally were interconnected to the long-distance providers. As access tandem switches represent an additional point of potential network failure, involve additional costs to the IXC, and impose additional delay on the process of call setup, the larger IXCs often terminate high-capacity trunks directly in the LEC COs or tandem switching centers. Thereby, the access tandem arrangement is bypassed. Where the physical space is available and can be securely partitioned, the LECs must lease space to the IXCs in order that they can collocate their termination facilities in the LEC CO. The cost to the IXC of such leased space is based on actual costs to the LEC plus a reasonable profit margin, at least theoretically. (Note: The LECs maintain that, in practice, the cost to the IXC is heavily discounted.)

The local loop functions to provide access to the carrier-provided Wide Area Network (WAN). Access facilities typically extend from the customer premises to the LEC CO exchange, with the demarcation point, or demarc, serving as the point of separation between the CPE and LEC domains. Generally, the incumbent LEC (ILEC) provides the access facilities, which terminate in the ILEC CO. A Competitive LEC (CLEC) may provide its own access facilities, typically in the form of optical fiber to areas where there is a significant concentration of high-volume commercial traffic. Access increasingly is provisioned through Wireless Local Loop (WLL) technologies, with various microwave systems typically used for this purpose, although infrared (IR) is an option. Alternatively, the CLEC may lease existing facilities from the ILEC in those states that support competition in the local loop. Access to voice networks increasingly is provided by Community Antenna TeleVision (CATV) providers using coaxial cables or Hybrid Fiber/Coax(HFC) transmission facilities to connect from the premises to the service provider's head end, where connection is established either to the LEC for access to the PSTN or to the Internet or other IP-based network for VoIP. In the United States as of June 30, 2005, end users obtained local telephone service by utilizing approximately 144.1 million ILEC switched access lines and 34.1 million CLEC switched access lines. Of the 34.1 million CLEC lines, approximately 9.1 million were provided over their own local loop facilities, of which 4.6 million were provided over CATV coaxial cable connections [11].

Access facilities also may provide direct connection from the customer premises to the IXC networks, bypassing the LEC switching systems in the process. The IXCs may provide those access loops themselves or they may lease them from the ILEC. Alternatively, end-user access to IXCs may be through loops leased from Competitive Access Providers (CAPs), also known as Alternative Access Vendors (AAVs). An access environment employs transmission facilities, switches, and signaling and control systems.

Transport is information transportation in the backbone of the PSTN, that is, within the cloud. Transport can be in the LEC domain or the IXC domain for long-haul applications. Either individually or in concert, and depending on the geographic scope of the communication, both LECs and IXCs may participate in information transport. Also, a third-party carrier, that is, a carrier's carrier, may provide the transport facilities. The transport domain also employs transmission facilities, switches, and signaling and control systems. In the United States as of June 30, 2005, ILECs were the presubscribed interstate long-distance carrier for about 49 percent of the switched access lines they provided. For CLECs, the percentage was 74 percent [11].

Services include a wide variety of options provided by LECs and IXCs. Such services include various discounted calling plans, custom-calling services, Centrex services, and toll-free (e.g., 800, 888, 877, and 866) calling. I discuss a number of services later in this chapter.

A community is known by its public utilities. The life of our country is built around them…. That such services may be extended and developed to be of the greatest use to the greatest number, the Federal Government and practically all of the states have appointed Public Service Commissioners as permanent tribunals to regulate public utilities with fairness to all concerned.

Telephone Almanac, American Telephone and Telegraph Company, 1922

There exists a complex set of domains that address regulatory and standards areas of responsibility. While it would be much simpler if these domains were discrete, they overlap nevertheless.

Regulation is largely nonexistent at the international level, although it is heavily influenced by the ITU-T, which is chartered by the United Nations (UN) and which previously was known as the Consultative Committee for International Telephone and Telegraph (CCITT). The original predecessor organization was the International Telegraph Union (ITU), which was formed in 1865 to ensure the interconnectivity of national telegraph networks. The ITU-T primarily is responsible for setting standards recommendations intended to ensure the interconnectivity of national networks. Specific standards recommendations also address voice, data, fax, and video applications. The International Telecommunication Union—Radiocommunication Sector (ITU-R), previously known as the Consultative Committee for International Radio (CCIR), governs over-the-air communications. Intelsat and other consortia are responsible for allocating and managing satellite orbital slots. The International Telecommunication Union—Development Sector (ITU-D) works to further telecommunications development around the world, especially in developing countries.

Regional authorities, although few in number, have the same responsibility as the ITU, but within a more compact region. Directorate General XIII (DG XIII), for example, is responsible for dealing with such issues of regulation and standardization within the European Union (EU), which largely comprises Western Europe. Previously known as the European Community (EC), the EU has real authority in the areas of regulation and standards, establishing and enforcing policy matters such as network competition within a member nation's network.

National regulation is critical in most areas of the world, although less so in the case of the EU member nations, as they have ceded a good deal of this responsibility to the regional authority. Many nations have well-defined and tightly enforced rules, regulations, and standards. Areas of influence often include such issues as competition, rates and tariffs, radio frequency spectrum allo-cation, and characteristics of electrical local loops. National authorities also deter-mine the basis on which international carriers can establish a presence at landing points for purposes of interconnection with the national networks. In the United States, the FCC is the national authority. Some countries have taken a much more light-handed approach. New Zealand is most unusual in that the national network was entirely deregulated and the regulator abolished some years ago, although the Telecommunications Act of 2001 placed the Commerce Commission back in that role as a competition authority with very limited power. The Australian Telecommunications Authority (AUSTEL) was disbanded in 1997 in favor of market self-regulation, although the Minister for Communications, Information Technology & the Arts has some responsibilities in this area, and two ombudsmen are appointed to deal with consumer complaints. Limited legislative and judicial controls remain in place in these countries.

Local regulation enters the picture relative to local zoning ordinances that variously address wireless tower placements, height limitations, and even aesthetics that might require a cellular telephone tower to masquerade as a pine tree or bell tower, for example. Local regulators in the United States also generally control CATV franchises and cable rights-of-way. In Milpitas, California, for example, the local regulators demanded the right to levy franchise taxes against Pacific Bell when the LEC sought right-of-way permission to lay fiber-optic cables to deliver CATV programming in competition with the incumbent CATV provider. PacBell refused to submit, arguing that it was subject only to state and federal regulation and not local regulation. As a result, the Information Superhighway ground to a halt in Milpitas in 1994.

In some instances, local regulation predominates. Alaska and certain Scandinavian countries are unusual in that they have many municipally owned LECs. Commercial carriers had no interest in providing service in such sparsely populated areas, given the high costs of provisioning and the low potential for revenues and profits. Note that many cooperatives were established for the same reasons.

Carriers in the United States traditionally have been required to file a set of tariffs with each appropriate regulatory authority. Those tariffs describe the services the carrier intends to offer in that domain, the rates it proposes to charge for them, and the proposed obligations, rights, and responsibilities of both the carrier and the customer. The regulatory authority examines the tariff filing, holds public hearings on the proposal, and renders a binding decision, which the carrier can appeal to the regulator or through the judicial system [12].

In the United States, national regulation is the domain of the FCC, which has the responsibility to determine all interstate issues, including radio frequency allocation. At the state level, the regulatory authority is in the form of a Public Utilities Commission (PUC) or Public Services Commission (PSC), which has the authority to regulate all exclusively intrastate matters not delegated to the municipalities and other local authorities.

Some years ago, and certainly prior to AT &T's divestiture of the Bell Operating Companies (BOCs) in 1984, the network in the United States was relatively simple in terms of its ownership and topology. Each operating telephone company provided service in its franchised serving areas and gained access to the AT&T long-distance network on a fairly straightforward basis. Beginning in the late 1920s, the network was organized on a layered basis, with five levels of hierarchy, known as classes [12].

· Class 4 offices are tandem toll centers, which serve to interconnect Class 5 offices not interconnected directly. As the lowest class of toll center, these also serve as the first point of entry to the long-distance, or toll, network. Class 4 offices are interconnected within a relatively local toll network and provide access to higher order toll centers. In many instances, a Class 4 office also serves as a Class 5 office; in other words, a hybrid Class 4/5 switch serves as both a Class 4 tandem toll office and a Class 5 CO, with the separate functions provided through logical and physical partitioning within the switch. Approximately 1500 tandem toll centers existed in North America prior to AT&T's divestiture of the BOCs. It is uncertain how many of them remain.

· Class 3 offices, or primary toll centers, are higher order toll centers, generally serving to connect Class 4 offices for intrastate toll calling. Class 3 offices typi-cally serve to interconnect independent telcos and BOCs. Approximately 200 such offices existed prior to divestiture. It is likely that most, if not all, have now been decommissioned.

· Class 2 offices, or sectional toll centers, serve to interconnect primary toll centers, largely for interstate calling within a geographic region such as the northeast or the southwest. Approximately 67 sectional toll centers existed in the AT&T network prior to divestiture. It is likely that most, if not all, have now been decommissioned.

· Class 1 offices, or regional toll centers, serve to interconnect sectional toll centers in support of interregional calling. There were 10 regional toll centers in place in the United States prior to divestiture. At the end of 2001, 7 remained in the United States and 2 in Canada. It is likely that most, if not all, have now been decommissioned.

As illustrated in Figure 5.3, the offices traditionally were interconnected on a hierarchical basis, with end offices residing at the bottom of the network food chain. As a user places a long-distance call, the Class 5 switch examines and analyzes the destination telephone number in the context of the geographic area it serves. Based on that information and relying on programmed logic, the CO processes and routes the call. Local long-distance calls (e.g., within the San Francisco Bay Area) are handled either by directly connected Class 5 offices or through a Class 4 tandem toll office that interconnects multiple Class 5 offices. A coast-to-coast call of only a few years ago, on the other hand, might have involved all five classes of the hierarchy.

This approach was quite sensible in the days when AT&T dominated the local and long-distance networks. As calls worked their way through the network, ever larger volumes of traffic were aggregated by ever more capable switches and shipped over trunks of ever greater capacity, taking advantage of the economies of scale.

This network topology has flattened over the years as the cost of transport over fiber-optic facilities has dropped, as the cost of switches has decreased, as hybrid Class 4/5 switches have been replaced by separate Class 4 and Class 5 switches, as competition has increased, and as traditional circuit-switched infrastructure has been replaced with Asynchronous Transfer Mode (ATM) and especially Internet Protocol (IP) infrastructure. As a result, there exist fewer switches, many of which are more intelligent and multifunctional and are interconnected by higher capacity transmission facilities in a sparse network configuration. As the various TDM–based offices have been decommissioned, many of them have been replaced with soft-switches, which are software-based and highly flexible, whereas TDM circuit switches are hard coded and highly inflexible. Softswitches can support multiple protocols, including perhaps TDM, Frame Relay, and IP.

CPE, as is noted earlier in the chapter, is the terminal and switching equipment located on the customer premises. While such equipment traditionally was rented to the subscriber by the LEC, deregulation generally places both the privilege and the responsibility of ownership on the end user in most countries. Similarly, inside wire and cable generally are deregulated.

The demarc constitutes the boundary between the end user and carrier domains. In a residential environment, the demarc is in the form of a Network Interface Unit (NIU). A NIU includes a protector, which serves to protect the premises wiring and equipment from aberrant voltages possibly induced by carrier power supplies, power utility transformers, or lightning strikes. Contemporary NIUs are intelligent, enabling telco technicians or automatic test systems to regularly test the integrity of the local loop from the CO to the customer premises. In the United States, the NIU is located outside the residence, perhaps on an outside wall or in the garage, because the regulated telco cannot place equipment inside the premises under the terms of the MFJ. (Note: On special request, the telco can install the demarc in a basement.)

In a business environment or a multitenant building, the demarc is positioned at the Minimum Point of Entry (MPOE), defined as the closest logical and practical point within the customer domain. In a high-rise office building, for example, it typically is defined as a point of the entrance cable 12 in. from the inside wall. Newer entrance cable facilities involve a physical demarc, while older facilities typically are tagged by telco technicians in order to indicate a logical point of demarcation. From that point inward, the cable and wire system is the responsibility of the user or building owner, as appropriate.

LECs provide local telephone service, usually within the boundaries of a metropolitan area, state, or province. Their primary charter is to provide local voice services through a network of local loops and COs, which can be connected either directly or through a tandem switch, as depicted in Figure 5.4. The LECs also provide short-haul, long-distance service, Centrex, certain enhanced services such as voice mail, and various data services. In the United States and many other developed nations, both Incumbent LECs (ILECs) and Competitive LECs (CLECs) exist. In many developing countries, only a single ILEC exists.

In addition to causing AT&T to divest the BOCs, the MFJ effectively limited the BOCs to providing basic voice and data services within defined geographical areas, known as Local Access and Transport Areas (LATAs). These services included intraLATA toll service, also known as local long distance, within the confines of the 196 defined LATAs. Additionally, the BOCs and RBOCs could not engage in certain other activities such as manufacturing communications equipment and providing enhanced services such as voice mail; subsequently, the latter restriction was lifted. LATAs now serve primarily as reference points for call routing.

In the United States, LECs traditionally had the exclusive rights to local and intraLATA markets, although many states either eroded or modified this policy; Connecticut, for example, has permitted local exchange competition since July 1, 1994. Although the Telecommunications Act of 1996 set the stage for complete and open competition for virtually all services, as it bogged down in the courts, the various state regulators took the initiative in terms of local service competition.

In addition to the RBOCs and their LEC subsidiaries, approximately 1300 independent telephone companies exist. GTE was the largest independent until Bell Atlantic acquired it in July 1999 to form Verizon Communications. Southern New England Telephone Company (SNET), which was partially owned by AT&T prior to the MFJ, was acquired by SBC in October 1998.

At this point, it is worth noting that the Telecommunications Act of 1996 has changed this landscape in a very dramatic way. Casting aside the MFJ, the act permitted the IXCs to begin competing immediately with the ILECs for local and intraLATA service. The act also allowed the RBOCs to offer interLATA long-distance service outside the states in which they operate as ILECs. Once the RBOCs satisfied certain local competition requirements, they were allowed to offer inter-LATA toll services within their home states as well. As competition intensified and both the ILECs and IXCs lost their dominance, interesting mergers began to take place, as noted above and below:

· SBC acquired AT&T in November 2005 to become AT&T, Inc.

· Verizon acquired MCI Worldcom in January 2006 to form Verizon Business.

· AT&T, Inc. acquired BellSouth in December 2006.

Competitive Local Exchange Carriers (CLECs) can compete for local service in most states. As of June 30, 2005, at least one CLEC was serving customers in 85 percent of U.S. postal ZIP codes, which include approximately 98 percent of the population [11]. While many CLECs originated as CAPs, others were IXCs, and still others were created specifically as CLECs. Metropolitan Fiber Systems (MFS), for example, originally was a facilities-based CAP. Subsequently, MFS acquired UUNET, a very large Internet access and backbone provider. MFS then was acquired by MCI, which then was acquired by Worldcom, with the combined company assuming the name MCI Worldcom. While MFS has lost its identity, the network that it constructed served MCI Worldcom well for IXC access and positioned it well as a CLEC. MCI Worldcom subsequently changed its name to Worldcom and then back to MCI after it was bankrupted by senior management. MCI later was acquired by Verizon, as previously noted.

IXCs are responsible for long-haul, long-distance connections across LATA boundaries. The IXC networks are connected to the LECs through Points of Presence (POPs), which typically are in the form of tandem switches. An interLATA call originating in a LEC serving area is recognized as such and is passed to the access tandem switch, which in turn passes the call to the IXC POP via dedicated trunks leased from the ILEC (see Figure 5.5). Alternatively, the IXC may collocate network termination equipment in the LEC exchange office, assuming that space is available and that secure physical separation can be established and maintained.

IXCs, by definition, are facilities-based carriers, or heavy carriers. While they prefer to contract directly with large end users, they also often work through non-facilities-based carriers (light carriers), including resellers, aggregators, and agents. Of the 400 or so heavy carriers in 2000, AT&T, MCI Worldcom, and Sprint domi-nated the market. Ultimately, however, they succumbed to various competitive forces. The tattered remnants of AT&T and MCI Worldcom eventually were absorbed by ILECs, and Sprint decided to focus on the wireless business.

Competitive Access Providers (CAPs), also known as Alternative Access Vendors (AAVs), provide an alternative means of connection between large user organizations and IXCs, completely bypassing the LEC network in the process. CAPs generally deploy high-capacity, fiber-optic facilities from IXC POPs to areas where there exist high densities of large user organizations (e.g., commercial office parks and urban business areas). In many cases, the CAP will extend the fiber-optic connection directly to the user's CPE, such as a PBX, as depicted in Figure 5.6. Wireless CAPs provide access on the basis of either various licensed microwave or infrared technologies.

CAPs operate most especially in the United States, where many now function as voice/data CLECs, providing Centrex service, local calling service, high-speed data services, and certain enhanced services.

International carriers provide communications transport services across national borders, based on access from the LEC or IXC domain by connection to an International Gateway Facility (IGF). Contemporary international carrier transmission facilities are largely satellite and submarine fiberoptic cables, the latter often jointly owned through consortia. Examples of international carriers include AT&T, Cable & Wireless (C&W), Global Crossing, and Verizon. International Record Carriers (IRCs) offer record communications services, which are services designed or used primarily to transfer information that originates or terminates in written or graphic form. Examples of record communications services include telex and TWX.

Overlay carriers build networks that overlay the traditional PSTN. While such networks are unusual in highly developed countries, they are common in developing nations. In some countries of eastern and central Europe, for example, private carriers have been franchised to build overlay digital microwave networks to provide service to large governmental, educational, and commercial organizations. In such cases, the PSTN simply could not be upgraded quickly enough to provide satisfactory communications, which are considered vital to economic growth. Overlay carriers generally deploy microwave systems that effectively overlay the outdated wireline facilities of the incumbent carriers.

5.4 SIGNALING AND CONTROL: EXPANDED VIEW

Only in rare instances can a telephone operator know how momentous are the spoken messages for which she established the connections. Life and death may depend upon the swiftness and sureness with which she handles any call. All Bell System telephone calls are treated as if marked "urgent." Methods of operation and mechanisms are so planned that every connection may be established with all possible speed. Bell System service was the fastest in the world ten years ago [1925], when the average time required to complete a long distance call was seven minutes. It is almost five times as fast today [1935].

Telephone Almanac, American Telephone & Telegraph Co., 1935

Signaling and control systems and networks also handle billing matters, perhaps querying centralized databases in the process. Billing options might include bill to originating number (e.g., DDD and WATS), bill to terminating number (e.g., INWATS, or toll-free), bill to third number (third party), and bill to calling card with verification of a PIN against a database.

Finally, certain network management information often is passed over signaling and control links. Such information is used for remote monitoring, diagnostics, fault isolation, and network control. In this fashion, a centralized Network Operations Center (NOC) can monitor the network, and faults or degradations in performance can be determined and isolated. Diagnostic routines can then be invoked in order to determine the specific nature of the difficulty. Finally, a network management system or network manager can instruct the network element in difficulty to resolve the problem, perhaps by resetting or reinitializing itself, or by disabling a failed port and activating a standby port.

In-band signaling and control functions take place over the same physical path as the conversation and occupy the same frequency band (analog) or time slots (digital). The impact of simultaneous data transfer and signaling over the same frequency range or time slots disrupts the information stream and, therefore, can be characterized as disruptive or intrusive. As a result, in-band signaling and control seldom is employed in contemporary networks, with the exception of analog local loops.

By way of example and in years past, I frequently called long distance to talk with my young son in East Texas. During those conversations, Barrett (my son) had the annoying habit of "accidentally" depressing the buttons on the tonepad with his chin. The resulting Dual-Tone MultiFrequency (DTMF) signals were interpreted by the network as a priority instruction set. Since the signaling tones occupy the same range of frequencies at the same moment in time as the conversation, they override and interfere with it. In contemporary networks, this in-band signaling and control technique actually is disruptive only over the local loops, which extend from the CPE to the edge of the network cloud; internally, the networks make use of out-of-band signaling and control. Nonetheless, Barrett got a set of tones in his ear and I got a set of tones in my ear; Barrett found this to be highly amusing, while I found it to be highly aggravating, which Barrett found to be even more amusing, and so on, and so on. (Note: James Barrett Horak is now a Sergeant in the United States Marine Corps. No longer is he easily amused, as it is against Marine Corps policy.)

Out-of-band signaling and control, in the simplest analog application, takes place over frequencies separate from those that carry the information. In a contemporary digital network, signaling and control data generally occupy separate, specifically designated time slots. In either case, there is no interference between the two functions. In other words, out-of-band signaling and control is termed to be nondisruptive or nonintrusive. Out-of-band signaling and control is the standard approach in digital networks and, most certainly, in the core of the carrier networks.

In 1916, the average time required to establish a Bell System long distance connection was approximately eleven minutes. By 1926, it had been reduced to 5.6 minutes. The average for 1936 was 1.4 minutes.

Telephone Almanac, American Telephone & Telegraph Company, 1937

The carriers use Common Channel Signaling (CCS) and control systems to carry large volumes of signaling and control information in support of high-traffic networks. The CCS links are digital in nature, based on packet switching, and often are in the form of a dedicated T1 channel over a high-speed optical fiber. Essentially, the CCS network is a highly robust subnetwork that supports the operations of the primary communications network. The CCS subnetwork connects the various network switches to centralized computer systems of significant intelligence and on which reside very substantial databases. Through the use of centralized intelligence supported by carefully synchronized databases, you can control the operations of an entire network and monitor its performance, from end to end. While complicated and expensive to design and deploy, CCS networks are more effective and less costly than the alternative of placing lesser levels of intelligence in each of the various network switches, each of which is required to perform redundant processes in complete harmony with the others.

5.5 NETWORK SERVICES

By means of what is known as Conference Service, a number of telephones, at widely scattered points, may be connected together so that their users may converse with each other as if they were all seated in the same room. Widely used for business purposes, it has its social uses also—as an antidote for loneliness.

Telephone Almanac, American Telephone & Telegraph Company, 1938

You can group network services into several categories that define their basic nature. Those categories include access services, dedicated services, switched services, and virtual services.

Access services are those services that provide circuit access to the network, which may be a LEC CO or an IXC POP. The circuits may be analog or digital and single-channel or multichannel. Access services include residential and business lines and PBX trunks.

Residential lines are local loop connections between the residential premises and the CO. Although generally analog in nature, the market penetration of digital ISDN Basic Rate Interface (BRI) local loops is relatively high outside the United States. Contemporary residential lines also can be provided over analog or digital channels of a DSL local loop or even over a CATV network. According to the 1951 Bell Telephone System Telephone Almanac:

Business lines are local loop connections between the business premises and the CO. Business lines provide access to single-line and multiline terminal sets as well as to Key Telephone Systems (KTSs). Business lines generally are analog in nature, although digital ISDN BRI has increased in popularity. Contemporary business lines also can be provided over analog or digital channels of a DSL local loop or even over a CATV network. Business lines are almost always private lines, although there are very rare instances of party line service in developing countries.

An Off-Premises eXtension (OPX) circuit is a dedicated PSTN circuit that connects a PBX or KTS to an extension voice terminal located off premises, that is, at another location some distance away. The terminal appears to the PBX exactly as though it were an on-premises extension, providing the user with the same level of functionality. OPXs are unusual, as both the circuit and the special-purpose system interface card are expensive. Additionally, and as contemporary users often are not office bound, voice mail, e-mail, cellular telephony, pagers, and other technologies are adequate alternatives for most situations.

Switched services include all typical local and long-distance voice traffic, whether inbound or outbound. Specific services in the United States include DDD, WATS, virtual WATS, INWATS, 500, and 900/976. Many other telcos around the world offer similar services and a great many other services under a wide variety of names. Deregulation, divestiture, and resulting competition have significantly reduced the costs of these services over the years. The emergence of specialized VoIP carriers has further intensified the price wars, and many long-distance services truly have become commodities, with any differentiation limited to pricing.

While the last manual exchange in the United States converted to dial many years ago, there are still a great number of manual exchanges in developing countries. Operators must still act on long-distance calls in some developing countries, particularly in the case of international calling where International DDD (IDDD) is not in place. In some developing countries it is still necessary to make an appointment call, which involves making an appointment for the international operator to seize an international trunk and place an international call at an appointed time. Message service, also known as a messenger call, is available in developing countries. This service involves the telephone company's sending a mes-senger to a remote village or other location with a message advising that person to expect an appointment call to be placed to a particular pay station, telco office, or agency in another village with telephone service; the cost of the messenger is added to the cost of the call.

In remote, rural areas of the United States, there remain a large number of non-dialable toll points. These toll points are six-digit numbers in the 88 X-NXX format. Operator intervention is required to access these telephone numbers, which terminate in locations that are beyond the reach of cable systems and are too low and sheltered to be reached via satellite. (The bottom of the Grand Canyon is one good example.)

WATS resembles DDD service but is billed according to a variety of discount plans for large user organizations. WATS originally required special-purpose outgoing trunks that had access to specific areas of the country. Intrastate WATS provided intrastate coverage only. Interstate WATS was organized according to mileage bands 1–5, which were pre-sented as crudely concentric areas of increasing geographic coverage. Band 1 reached adjacent states, band 2 included the next concentric ring of states, band 3 the next ring, band 4 the next ring, and band 5 provided full coverage of the 48 contiguous states. The greater the area of coverage was, of course, the higher the cost of the WATS service was. Traditional WATS was provided on a full-time or a measured basis. You could categorize full-time WATS as "all-you-can-eat" WATS because it was billed at a flat rate, with no usage monitoring or billing. Part-time, or measured, WATS was billed on a flat rate for the first 10 or 20h of usage, with overtime charges applying to traffic over the threshold. Clearly, the process of analyzing traffic patterns and configuring an optimum WATS network, with overflow to DDD, could be a fairly complex process.

Also known as 800 Service, Inward WATS (INWATS) resembles virtual WATS, with the charges billed to the called party. Therefore, the call is toll free, at least to the caller. INWATS (1.800) service became so popular in the United States that the supply of numbers was exhausted several years ago. Therefore, 888 numbers were added, and 877 and 866 numbers were added soon afterward. Future additions will follow this existing convention of 8 NN, with the last two numbers being identical. Outside the United States, INWATS service is known by various terms, including FreeCall, Freephone, Greenphone, and Green Number, and is accessed through various dialing conventions, including 080, 0800, and 0500. In 1997 the ITU-T implemented a Universal International Freephone Number (UIFN) convention, which involves dialing 800 + 8 digits.

INWATS is an effective means of encouraging current and prospective customers to call, because they incur no toll charges. Incoming call centers, therefore, are heavy users of INWATS, often terminating large numbers of INWATS numbers in a single call center. An ACD in a call center often is equipped to recognize the INWATS number called, with the called number being delivered to the system through the Dialed Number Identification Service (DNIS), which generally is provided by the carrier at additional cost, although it may be a no-cost feature of ISDN PRI trunks. Based on the DNIS and other information, the ACD can route the incoming call to the optimal agent group and agent with greater effectiveness and efficiency, delivering a screen pop in the process.

INWATS also is a cost-effective means for telecommuters and mobile employees to access various company offices for both voice and data applications. With the billing reversed to the target number, the company is relieved of the cost of processing expense vouchers for telephone charges. Further, the cost of the call often is far less than if it were charged to a calling card.

INWATS was the first instance of an Intelligent Network (IN) service. The INWATS numbers dialed do not represent real telephone numbers, at least not in the classic sense. In other words, they do not conform to the standard numbering scheme, wherein a telephone number (logical address) relates directly to a physical location (physical address) based on a standard numbering convention. Rather, an INWATS number can be directed to any location within the carrier's domains. In order to direct the call to the proper physical location, the network must query a database of INWATS numbers to translate that number into a conventional number associated with a specific physical location. Additionally, the database advises the originating LEC as to how the call should be routed. In the case of an interLATA call, the call routes to the IXC with which the target user has an INWATS relation-ship [15].

AT&T offered a similar service some years ago in the form of 700 service. The service provided follow-me call forwarding, although only AT&T long-distance subscribers could access a 700 number. No companies currently market 700 services [17–19]. Note: In some countries, 700 and 0700 numbers are designated other purposes such as for Internet calls, which may be billed at a different rate than voice calls.

The 900/976 services are premium information services that carry either a flat cost per call or the cost per minute that the called party (sponsoring party) determines. The revenues are divided among the sponsoring party receiving the call and the various carriers involved. Originally intended for applications such as telethons and informational services, 900/976 services have gained a bad reputation because many providers of telephone sex and other questionable services make extensive use of them. As a result, 900/976 services have fallen out of favor and are not widely used any longer. Fraud schemes actively use 900/976 numbers. In such a scheme, a caller will leave a message asking for a return call to a 900/976 number, with the call carrying an exorbitant charge.

Virtual Private Network (VPN), or Software-Defined Network (SDN), services are intended for use by very large user organizations. Classic voice VPNs are circuit switched in nature, creating the effect of a private, leased-line network but without the associated issues of design complexity, long deployment time, high recurring cost, and vulnerability to failure. VPN services generally are inter-exchange, and often international, in nature because they find their greatest application in large multisite enterprises that transcend local boundaries. To configure a VPN, it is necessary to identify each terminating location in the multisite enterprise and the level of bandwidth required by each. Dedicated access circuits are established between each point of termination and the closest VPN-capable POP (Figure 5.8). Rather than interconnecting the various sites with dedicated circuits, the carrier routes the traffic over high-capacity transmission facilities on a priority basis, with the paths identified in switch routing tables. This ensures that the level of service provided is roughly equivalent to that of a true private network. The carrier realizes the benefit of sharing the involved network with other users, and at least a portion of those cost savings are reflected in lower network costs to the VPN customer.

You can define value-added services, also known as enhanced services, as those that alter the form, content, or nature of the information, thereby adding value to it. Examples include store-and-forward services such as voice mail, e-mail, and fax mail. In the data realm, networks that accomplish the process of protocol conversion are considered as providing value-added services.

5.6 PORTABILITY: A SPECIAL ISSUE

In the United States, 800 numbers (currently 888, 877, and 866 as well) have been portable across carriers since 1992 (although subject to restriction by LATA boundary). Portability of local numbers became an issue of great significance in the mid-1990s, when a small number of states began to permit competition in the local exchange. As the CLECs began to provide local service, they attacked the installed base of large ILEC customers. They were forced to require that those customers change their telephone numbers to fit into a block of DID numbers leased by the CLEC from the ILEC. Regardless of the attractiveness of the CLEC service offerings, potential customers were understandably reluctant to undergo a number change, which could involve a potentially significant loss of business, potentially considerable costs for reprinting stationary and otherwise advertising the new number, and an obvious disruption in the business of the enterprise. Further, customers would have to change numbers again if they were unhappy with the new provider and, therefore, choose either to return to the ILEC or to switch to another CLEC. The issue grew exponentially with the drafting of the Telecommunications Act of 1996 and the expectation that the CLEC business would experience dramatic growth.

Therefore, the act mandated the establishment of the Local Number Portability Administration (LNPA) to oversee the development and deployment of a mechanism for Local Number Portability (LNP). The first implementation of LNP was in the state of Illinois, which was among the first to permit competition in the local exchange and which has served as the model for the current method. That method involves the use of a Local Routing Number (LRN) of 10 digits and makes use of both the SS7 signaling and control network and the Advanced Intelligent Network (AIN) that SS7 supports. When a caller dials a telephone number, the originating CO consults a Service Control Point (SCP), which dips into a regional database. The database, as appropriate, provides the LRN, as well as the Carrier Identification Code (CIC) of the CLEC, in order that the call can route to the competitive carrier. Number Portability Administration Centers (NPACs) serve as clearinghouses for all local operators. Neustar, which currently is responsible for administration of the North American Numbering Plan (NANP), operates the NPACs. Note that LNP, as the name suggests, is local in nature; in other words, the number is portable between LECs only within the local calling area supported by the serving LEC (i.e., not across ILEC domains and not between calling areas involving toll calls).

As a footnote, 500 numbers and 900 numbers, both of which are geographically independent, are not portable across carriers, although the FCC has determined that such portability lies in the public interest [19, 20].

5.8 VoIP: NEXT-GENERATION PSTN

The future of the telephone holds forth the promise of a service, growing always greater and better, and of continued progress—the end of which no one can foresee.

Telephone Almanac, American Telephone and Telegraph Company, 1927

The incumbent voice carriers all built their networks around circuit switching. As they converted from analog to digital technology, they introduced TDM, ISDN, and SS7, but circuit switching remained the technological network foundation. The carriers introduced Asynchronous Transfer Mode (ATM) into the backbone in the mid-1980s, and by the early 1990s ATM was touted as the ultimate network-switching technology in the WAN and even in the Local Area Network (LAN) domain. Ethernet overwhelmed ATM in the LAN and the Internet Protocol (IP) is doing the same thing in the WAN. While I discuss the details of Synchronous Optical NETwork (SONET) fiber optics, ATM switching, IP, data compression, and other elements of the VoIP mix in other chapters, I find it appropriate to discuss the overall concept now as VoIP seems certain to be the foundation for the next-generation PSTN. More correctly, IP will be the dominant protocol in the next generation of networks. These networks will support a multimedia blend of voice, audio, data, fax, image, and video at broadband speeds.

As noted previously, voice originates as an acoustic signal. In order to transmit voice over a network, it must first be converted to an analog electrical signal format. To send that voice signal over a digital network, it must be encoded into a digital (data) format, and it must be decoded back into an analog signal on the receiving end. The standard encoding technique is Pulse Code Modulation (PCM), which requires that the analog signal be sampled 8000 times per second at precise and regular intervals of 125 μs (microseconds), which represents 1/8000th of a second. In other words, each sample represents exactly 125 μs of a voice information stream. Each of the PCM samples comprises eight data bits, or one data byte (think of it as a sound byte). The string of sound bytes in a voice conversation, according to the normal conventions, requires a 64-kbps channel, also known as a DS-0 (Digital Signal level Zero), which is the fundamental building block of all digital telephony. A sound byte might represent an utterance or it might represent a moment of silence (i.e., a silence byte). A voice transmission contains lots of moments of silence. Further, the human conversational convention generally involves only one active direction of the conversation at a given time. In other words, we take turns talking, rather than overtalking each other. Therefore, a circuit supporting a voice conversation generally is silent in one direction or the other.

1. The process of compression and decompression takes some time—not much time, but some.

2. The packets can encounter considerable delay, or latency, as they transverse the network. If the network is under a relatively light load at a particular instant, the routers and switches can fairly instantly process the packet, and the links can become available almost immediately. If the network is under relatively heavy load at a particular instant, the packet might queue up for a much longer period of time. The more routers, switches, and links that are involved along a chosen path, the greater the latency.

3. The level of delay is variable and unpredictable in nature. This variability in latency is known as jitter.

4. The stream of packets might take a relatively short physical path on one call and a relatively long path on the next call, all depending on the load on the network at the time. The longer the path taken, the greater the propagation delay involved. The more devices (e.g., routers and switches) involved, the more processes involved, and the greater the cumulative delay as the processes are performed.

5. Individual packets in a stream of packets might take different physical paths. Again, the longer the path taken, the greater the propagation delay involved. The more devices (e.g., routers and switches) involved, the more processes involved, and the greater the cumulative delay as the processes are performed. Note that each packet is treated individually. The final result can be an unac-ceptable level of jitter, even if the packets arrive in the proper sequence. If the packets arrive out of sequence, some process must be invoked to resequence them in order that they can play in the proper order. If some packets are delayed too long, they may not arrive in time to play in the proper order, in which case they are rejected.

6. Individual packets might suffer errors in transit. Errored data are of no value. In fact, errored data are of decidedly negative value. Once the packet arrives, if ever, it must either be accepted or rejected. There is no time for a retransmission of an errored voice data packet.

So, the inherent nature of the packet network is problematic. While this approach offers great efficiencies, it also imposes variable and unpredictable levels of delay on the packets. In other words, VoIP is a classic design trade-off between cost and performance. Next-generation VoIP networks propose to optimize this trade-off in several ways:

1. Voice over IP carriers deploy gateways only at the edges of the network, where the most complex decisions must be made and where the most involved (read time-consuming) processes must be invoked. They deploy high-speed ATM switches in the core of the networks, where speed is of the essence. The routers and switches currently can run at internal bus speeds in the range of 1 Tbps, at least according to the design specifications.

3. The carriers deploy incredibly high-speed optical fiber transmission systems in the core. Along any given path, there may be hundreds of fibers, each of which can support numerous lambdas, each of which can run at rates in the Gbps range.

4. The compression algorithms are extreme. Traditional PCM voice requires 64 kbps. Voice over IP requires as little as 5.3 kbps, depending on the specific algorithm selected, plus IP overhead. (Note: With the IP overhead, the brings the bandwidth requirement back up to approximately 64 kbps, so clearly VoIP is not all about reducing bandwidth requirements.)

To illustrate the concept of compressed, packetized voice, consider the following analogy. You have become concerned about your health. You finally decided to take your grandmother's advice and include a bowl of stewed prunes in your daily diet. (Your grandmother has lived a long and healthy life but is not much of a gourmet!) You call your grandmother and ask her to pick some prunes from her orchard and send them to you on a regular basis. Daily, your grandmother picks the ripest prune plums (bytes) at an exact pace (samples at precise intervals), puts 160 of them (data set) in a bowl (buffer), dehydrates (compresses) them, removing the water (silence) in order to reduce their weight and volume (bandwidth) and lower the cost of postage (network cost). The result is prunes. Every day she sends you a small, numbered box (packet) of prunes through the mail, along with specific instructions that you eat them every day, at exactly the same time of the morning, and in exactly the same order in which she mailed them to you. In that fashion, you always will have fresh prunes for breakfast and you will remain regular (perfectly timed). You follow her instructions precisely for some number of days. Each day you open a box of prunes, put them in a bowl (buffer) and soak the contents in order to reinsert the water (silence), thereby reconstituting (decompressing) them to an approximation of their original form. Then disaster strikes. One box (packet) of prunes (sound bytes) arrives in sequence but crushed (errored). As the contents (compressed voice payload) are inedible (unintelligible), you throw away (discard) the box and its contents. The next day, the postal system fails you, and no box of prunes arrives (latency, or delay). The next day, two boxes arrive (jitter); you eat two bowls of prunes for breakfast and regret it. You call your grandmother and ask her to send the daily prune ration via Federal Express (high-speed network). They almost always arrive every day and at exactly the same time. Each box (packet) still wends its way through the network independently, but the overbuilt (broadband) network of high-speed access circuits (couriers), high-speed jumbo jets (transport circuits), and high-speed airports and processing centers (routers and switches) provides a good balance of cost and performance. Federal Express does such a good job that it lowers its costs. You are such a good customer that Federal Express offers you a discount; the total cost compares favorably to that of growing your own prune plums.