601 Assignment 8 & Discussion 8

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Chapter Ten

The Internet

Data Communications and Computer Networks: A Business User’s Approach

Eighth Edition

After reading this chapter,
you should be able to:

Discuss the responsibilities of the Internet Protocol (IP) and how IP can be used to create a connection between networks
Identify both IPv4 and IPv6 addresses
Discuss the responsibilities of the Transmission Control Protocol (TCP) and how it can be used to create a reliable, end-to-end network connection

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

After reading this chapter,
you should be able to (continued):

Identify the relationships between TCP/IP and the protocols ICMP, UDP, ARP, DHCP, NAT, and tunneling protocols
Describe the responsibility of the Domain Name System and how it converts a URL into a dotted decimal IP address

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

After reading this chapter,
you should be able to (continued):

Describe the major Internet applications and services
Recognize that the Internet is constantly evolving and that IPv6 and Internet2 demonstrate that evolution

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Introduction

Today’s present Internet is a vast collection of thousands of networks and their attached devices
The Internet began as ARPANET during the 1960s
One high-speed backbone connected several university, government, and research sites
Backbone was capable of supporting 56 kbps transmission speeds and eventually became financed by the National Science Foundation (NSF)

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Introduction (continued)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Internet Protocols

To support the Internet and all its services, many protocols are necessary
Some of the protocols that we will look at:
Internet Protocol (IP)
Transmission Control Protocol (TCP)
Address Resolution Protocol (ARP)
Dynamic Host Configuration Protocol (DHCP)
Network Address Translation (NAT)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Internet Protocols (continued)

Recall that the Internet with all its protocols follows the TCP/IP protocol suite (Internet model)
An application, such as e-mail, resides at the highest layer
A transport protocol, such as TCP, resides at the transport layer
The Internet Protocol (IP) resides at the Internet or network layer
A particular media and its framing resides at the network access (or data link) layer

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Internet Protocols (continued)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

The Internet Protocol (IP)

IP prepares a packet for transmission across the Internet
The IP header is encapsulated onto a transport data packet
The IP packet is then passed to the next layer where further network information is encapsulated onto it

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

The Internet Protocol (IP) (continued)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

The Internet Protocol (IP) (continued)

There are currently two versions of IP:
Version 4, which has been in existence for many years
Version 6, which has been available for several years but is only now starting to see a substantial move towards replacing version 4
Let’s take a look at both versions

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IPv4

Using IPv4, a router:
Makes routing decisions based on the 32-bit destination address
May have to fragment the datagram into smaller datagrams using Fragment Offset
May determine that current datagram has been hopping around the network too long and delete it (Time to Live)

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The IPv4 Header/Datagram

Figure 10-4

Format of the IPv4 datagram

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

IPv4

Fragmenting an IPv4 datagram is performed by the Offset and More fields. Offset value is in multiples of 8 bytes

Figure 10-5

Division of an IPv4 datagram into three fragments

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IPv4 Addresses

All devices connected to Internet have a 32-bit IP address
Think of the IP address as a logical address (possibly temporary), while the 48-bit address on every NIC is the physical, or permanent address
Computers, networks and routers use the 32-bit binary address, but a more readable form is the dotted decimal notation

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IPv4 Addresses (continued)

For example, the 32-bit binary address

10000000 10011100 00001110 00000111

translates to

128.156.14.7

in dotted decimal notation

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IPv4 Addresses (continued)

When IP addresses were originally created, they were called classful addresses
That is, each IP address fell into particular class
A particular class address has a unique network address size and a unique host address size
There are basically five types of IP addresses: Classes A, B, C, D and E

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IPv4 Addresses (continued)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

IPv4 Addresses (continued)

When you examine the first decimal value in the dotted decimal notation:
All Class A addresses are in the range 0 - 127
All Class B addresses are in the range 128 - 191
All Class C addresses are in the range 192 – 223
All Class D addresses are in the range 224 – 239
All Class E addresses are in the range 240 - 255

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IPv4 Addresses (continued)

IP subnet masking
Sometimes you have a large number of IP addresses to manage
By using subnet masking, you can break the host ID portion of the address into a subnet ID and host ID
Example – subnet mask 255.255.255.0 applied to a class B address will break the host ID (normally 16 bits) into an 8-bit subnet ID and an 8-bit host ID

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IPv4 Addresses (continued)

Today, IP addresses are considered classless addresses
With classless addressing, companies (users) do not apply for particular class of addresses
Instead, company will get its IP addresses from an Internet service provider (ISP)
Most ISPs have already applied for a large number of IP addresses and are willing to lease those addresses to companies

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IPv4 Addresses (continued)

Example – instead of applying for two Class C addresses, a company could contact an ISP, which would lease 500 IP addresses to the company
The addresses are not identified by any class – they are simply a contiguous block of IP addresses
Classless addressing has led to a much more efficient allocation of the IP address space
A company can lease only as many addresses as it needs

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Classless IPv4 Addresses

An IP address in slash notation has all the info we need about the block of addresses assigned to a user/company
For example, one address in a block of addresses is 167.199.170.82/27
27 bits belong to the network ID, and 5 bits belong to the host ID (IPv4 addresses have 32 bits)
The network mask has 27 1s followed by 5 0s. In dotted decimal notation that is 255.255.255.224.
The number of addresses in the block is 25 = 32

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Classless IPv4 Addresses

To find the first address, AND the address (167.199.170.82) with the network mask (255.255.255.224)

Address: 10100111 11000111 10101010 01010010

Mask: 11111111 11111111 11111111 11100000

Result: 10100111 11000111 10101010 01000000

Which in decimal is 167.199.170.64/27

The last address is 31 addresses past the first, or 167.199.170.95/27

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IPv6

The next version of the Internet Protocol
Main features include:
Simpler header
128-bit IP addresses
Priority levels and quality of service parameters
No fragmentation

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IPv6 (continued)

Figure 10-6

The fields in the IPv6 header

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

IPv6 Addresses

IPv6 addresses are 128-bits in size (2128 is a very large number!)
They are also classless addresses, similar to IPv4 addresses
Because of their size, a number of conventions have been adopted:

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IPv6 Addresses

Binary addresses are written using the short-hand hexadecimal form:

0110 1010 0011 1110 1011 1010 … 1110 1111

6A3E : BA91 : 7221 : 0000 : 01FC : 922C : 877B : FFEF

Four hex 0s in a row are truncated as follows:

6A3E : BA91 : 7221 : 0 : 01FC : 922C : 877B : FFEF

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IPv6 Addresses

Longer strings of 0s can be abbreviated further. For example,

6A3E : BA91 : 0 : 0 : 0 : 0 : 877B : FFEF

can be abbreviated as

6A3E : BA91 : : 877B : FFEF

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The Transmission Control Protocol (TCP)

TCP layer creates connection between sender and receiver using port numbers
The port number identifies a particular application on a particular device (IP address)
TCP can multiplex multiple connections (using port numbers) over a single IP line

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The Transmission Control Protocol (TCP) (continued)

The TCP layer can ensure that the receiver is not overrun with data (end-to-end flow control) using the Window field
TCP can perform end-to-end error correction
Checksum
TCP allows for the sending of high priority data
Urgent Pointer

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The Transmission Control Protocol (TCP) (continued)

Figure 10-7

The fields of the TCP header

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Internet Control Message Protocol (ICMP)

ICMP
Used by routers and nodes
Performs error reporting for the Internet Protocol
ICMP reports errors such as invalid IP address, invalid port address, and the packet has hopped too many times

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User Datagram Protocol (UDP)

A transport layer protocol used in place of TCP
Where TCP supports a connection-oriented application, UDP is used with connectionless applications
UDP also encapsulates a header onto an application packet but the header is much simpler than TCP (16-bit source port, 16-bit dest port, 16-bit length of entire packet, 16-bit checksum)

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Multiprotocol Label Switching

An additional layer often added above TCP
Used to move Internet packets more quickly through routers
By using the MPLS label, the router does not have to “dig in” so deep to retrieve IP address
The 20-bit Label field is the key identifier that connects this packet with a particular flow of packets

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Multiprotocol Label Switching

Figure 10-8

Two MPLS headers and their four fields

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Address Resolution Protocol (ARP)

When an IP packet has traversed the Internet and encounters the destination LAN, how does the packet find the destination workstation?
Even though destination workstation may have an IP address, a LAN does not use IP addresses to deliver frames
A LAN uses MAC layer address
ARP translates IP address into MAC layer address so frame can be delivered to proper workstation

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Dynamic Host Configuration Protocol (DHCP)

An IP address can be assigned to a workstation permanently (static assignment) or dynamically
Dynamic IP address assignment is a more efficient use of scarce IP addresses
When DHCP client issues an IP request, DHCP server looks in its static table
If no entry exists, server selects an IP address from available pool

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Dynamic Host Configuration Protocol (DHCP) (continued)

The address assigned by DHCP server is temporary
Part of agreement includes specific period of time
If no time period specified, the default is one hour
DHCP clients may negotiate for a renewal before the time period expires

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Network Address Translation (NAT)

NAT lets router represent entire local area network to Internet as single IP address
Thus, all traffic leaving LAN appears as originating from global IP address
All traffic coming into this LAN uses this global IP address
This security feature allows a LAN to hide all the workstation IP addresses from the Internet

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Network Address Translation (NAT) (continued)

Since the outside world cannot see into LAN, you do not need to use registered IP addresses on inside LAN
We can use the following blocks of addresses for private use:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255

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Network Address Translation (NAT) (continued)

When a user on inside sends packet to outside, the NAT interface changes the user’s inside address to global IP address
This change is stored in a cache
When the response comes back, the NAT looks in cache and switches the addresses back
If not the packet is dropped
Unless NAT has a service table of fixed IP address mappings
This service table allows packets to originate from the outside

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Tunneling Protocols and Virtual Private Networks (VPNs)

The Internet is not normally a secure system
If person wants to use Internet to access corporate computer system, how can a secure connection be created?
One possible technique is by creating a virtual private network (VPN)
VPN creates a secure connection through the Internet by using a tunneling protocol

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The World Wide Web

The World Wide Web (WWW) – immense collection of web pages and other resources that can be downloaded across the Internet and displayed on a workstation via a web browser and is the most popular service on the Internet
Basic web pages are created with the Hypertext Markup Language (HTML)
Hypertext Transport Protocol (HTTP) is protocol to transfer a web page

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Locating a Document on the Internet

Every document on the Internet has a unique Uniform Resource Locator (URL)
All URLs consist of four parts:
Service type
Host or domain name
Directory or subdirectory information
Filename

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Locating a Document on the Internet (continued)

Figure 10-9

The parts of a Uniform Resource Locator (URL) for HTTP (a) and FTP (b)

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

Locating a Document on the Internet (continued)

When a user, running a Web browser, enters a URL, how is URL translated into an IP address?
Domain Name System (DNS) – large, distributed database of URLs and IP addresses
The first operation performed by DNS is to query a local database for URL/IP address information
If local server does not recognize address, the server at next level will be queried
Eventually root server for URL/IP addresses will be queried
If root server has answer, results are returned
If root server recognizes domain name but not extension in front of domain name, root server will query server at domain name’s location
When domain’s server returns results, they are passed back through chain of servers (and their caches)

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Internet Services

The Internet provides many types of services, including several very common ones:
Electronic mail (e-mail)
File transfer protocol (FTP)
Remote login (Telnet)
VoIP (Voice over IP)
Listservs
Streaming audio and video
Instant Messaging, Tweets, and Blogs

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Electronic Mail (e-mail)

E-mail programs can create, send, receive, and store e-mails, as well as reply to, forward, and attach non-text files
Multipurpose Internet Mail Extension (MIME) is used to send e-mail attachments
Simple Mail Transfer Protocol (SMTP) is used to transmit e-mail messages
Post Office Protocol version 3 (POP3) and Internet Message Access Protocol (IMAP) are used to hold and later retrieve e-mail messages

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File Transfer Protocol (FTP)

Used to transfer files across the Internet
User can upload or download a file
The URL for an FTP site begins with ftp://…
The three most common ways to access an FTP site are:
Through a browser
Using a canned FTP program
Issuing FTP commands at a text-based command prompt

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Remote Login (Telnet)

Allows a user to remotely log in to a distant computer site
User usually needs a login and password to access a remote computer site
User saves money on long-distance telephone charges

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Voice Over IP (VoIP)

The transfer of voice signals using a packet-switched network and the IP protocol
Voice over IP (VoIP) can be internal to a company (private VoIP) or can be external using the Internet
VoIP consumes many resources and may not always work well, but can be cost-effective in certain situations

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Voice Over IP (continued)

Three basic ways to make a telephone call using VoIP:
PC to PC using sound cards and headsets (or speakers and microphone)
PC to telephone (need a gateway to convert IP addresses to telephone numbers)
Telephone to telephone (need gateways)

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Voice Over IP (continued)

Three functions necessary to support VoIP:
Voice must be digitized (PCM, 64 kbps, fairly standard)
64 kbps voice must be compressed
Once the voice is compressed, the data must be transmitted

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Voice Over IP (continued)

How can we transport compressed voice?
H.323
Created in 1996 by ITU-T
Actually, H.323 created for a wide range of applications both audio and video, and not for TCP/IP networks
Session Initiation Protocol (SIP)
Created by IETF specifically for supporting the transfer of voice over the Internet
Many feel SIP will surpass H.323

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Voice Over IP (continued)

ENUM
A protocol that supports VoIP
Converts telephone numbers to fully qualified domain name addresses
Example – telephone number (312) 555-1212 will be converted to 2.1.2.1.5.5.5.2.1.3.1.e164.arpa

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Listservs

A popular software program used to create and manage Internet mailing lists
When an individual sends an e-mail to a listserv, the listserv sends a copy of the message to all listserv members
Listservs can be useful business tools for individuals trying to follow a particular area of study

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Streaming Audio and Video

The continuous download of a compressed audio or video file, which can be heard or viewed on the user’s workstation
Real-Time Protocol (RTP) and Real-Time Streaming Protocol (RTSP) support streaming audio and video
Streaming audio and video consume a large amount of network resources

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Instant Messaging, Tweets, and Blogs

IM allows a user to see if people are currently logged in on the network and to send short messages in real time
Consumes less resources than e-mail, and faster
Tweets occur when you Twitter. Max 140 character messages
Blogs are online web logs that people maintain

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The Internet and Business

E-Commerce – the buying and selling of goods and services via the Internet
Many agree that e-commerce consists of four major areas:
E-retailing
Electronic data interchange (EDI)
Micro-marketing
Internet security

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Cookies and State Information

A cookie is data created by a Web server that is stored on the hard drive of a user’s workstation
This state information is used to track a user’s activity and to predict future needs
Information on previous viewing habits stored in a cookie can also be used by other Web sites to provide customized content
Many consider cookies to be an invasion of privacy

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Intranets and Extranets

An intranet is a TCP/IP network inside a company that allow employees to access the company’s information resources through an Internet-like interface
When an intranet is extended outside the corporate walls to include suppliers, customers, or other external agents, the intranet becomes an extranet

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The Future of the Internet

Various Internet committees are constantly working on new and improved protocols
Examples include:
Internet Printing Protocol
Internet fax
Extensions to FTP
Common Name Resolution Protocol
WWW Distributed Authoring and Versioning

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Internet2

A new form of the Internet is being developed by a number of businesses and universities
Internet2 will support very high-speed data streams
Applications might include:
Digital library services
Tele-immersion
Virtual laboratories

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The Internet In Action: A Company Creates a VPN

A fictitious company wants to allow 3500 of its workers to work from home
If all 3500 users used a dial-in service, the telephone costs would be very high

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The Internet In Action: A Company Creates a VPN (continued)

Figure 10-10

CompuCom employees dialing directly into the corporate computing center

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

The Internet In Action: A Company Creates a VPN (continued)

Instead, the company will require each user to access the Internet via their local Internet service provider
This local access will help keep telephone costs low
Then, once on Internet, company will provide software to support virtual private networks
The virtual private networks will create secure connections from the users’ homes into the corporate computer system

Data Communications and Computer Networks: A Business User's Approach, Eighth Edition

The Internet In Action: A Company Creates a VPN (continued)

Figure 10-11

CompuCom’s employees using a tunnel across the Internet into the corporate computing center

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Summary

To support Internet, many protocols, such as IP, TCP, ICMP, UDP, ARP, DHCP, and NAT, are necessary
The Internet Protocol provides a connectionless transfer of data over a wide variety of networks
There are currently two versions of IP: IPv4 and IPv6
The Transmission Control Protocol (TCP) resides at the transport layer and provides an error-free, end-to-end connection
The Internet Control Message Protocol (ICMP) performs error reporting for IP

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Summary (continued)

The User Datagram Protocol (UDP) provides a connectionless transport layer protocol in place of TCP
The Address Resolution Protocol (ARP) translates an IP address into a CSMA/CD MAC address on a LAN
The Dynamic Host Configuration Protocol (DHCP) allows a network to dynamically assign IP addresses to workstations as they are needed
Network Address Translation (NAT) allows a network to replace local IP address with on global-type IP address

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Summary (continued)

Tunneling protocols allow a company to create virtual private network connections into a corporate computing system
World Wide Web is vast collection of electronic documents containing text and images that can be accessed by simply clicking link within browser’s Web page
To locate document on Internet, you usually refer to its Uniform Resource Locator (URL)

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Summary (continued)

Internet consists of many commonly used network applications
E-commerce is the buying and selling of goods and services electronically
Cookies store state information on user’s hard drive and provide a way for Web sites to track a user’s Web-browsing patterns and preferences

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Summary (continued)

Intranet is in-house Internet with Web-like services that are available only to a company’s employees or to customers and suppliers through an extranet
The Internet continues to evolve with a completely new, higher-speed Internet2

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