Chapter 5 Book Notes: Data Communicating and Networking
1. How computers are connected
a. Roles: Sender/Receiver - sender=transmitter; receiver=listener
b. Communication Channel - an electronic or optical highway that carries a
communication signal between computers or other electronic devices.
c. Bandwidth - transmission speed which dictates the amount of data that can be
moved over the channel per unit of time. The measure of a channel’s capacity.
c.i. Measurement - bps; bits per second.
d. Channel speed - carries communication signals between computers and other
network devices.
d.i. Guide Media - physical and wire-like.
d.i.1. Twisted pair - ordinary telephone wire.
d.i.2. Coaxial cable - thick copper wire surrounded by insulating
material which itself is surrounded by an electrical conductor
formed as braided mesh. A protective plastic coating covers the
whole package.
d.i.2.a. High speed transmission
d.i.3. Fiber optics - the glass or plastic cable itself that is
transparent and carries light waves.
d.i.3.a. Signal is carried by light, data travels at the speed of
light
d.i.4. Wireless Media - channels with media not tied to wires and
cables. Easier installation and lower cost.
d.i.4.a. Microwave - the use of a radio to carry a
communication signal.
d.i.4.b. Infrared - light carries the signal but has the same
line of sight restriction. Mostly used for communication
within the same room
d.i.4.c. Satellite - overcome the distance limitations. An
earth station sends a signal up to an orbiting satellite where
the signal bounces back to another earth station.
d.i.4.d. Radio Frequency (RF) - wireless technology.
d.i.4.d.i. Bluetooth - specific radio frequency wireless
connection limited to very short distances. Used for
connection between computers and peripheral
devices.
2. How a channel works-
a. Protocol - an established procedure of conduct.
3. WAN vs. LAN -
a. Wide Area Network (WAN) - covers a large geography and includes connections
to many MANs (metropolitan area networks) or LANs (local area networks).
Largest WAN is the Internet.
b. Local Area Network (LAN) - single geographical area. Provide local connectivity
and permit sharing of resources among users.
4. LAN topologies -
a. Bus topology - a single cable (bus) that all computers and other devices are
connected to (but not in a loop). Least expensive to wire.
b. Star topology - involves a collection of nodes (terminals or workstations)
connected to a single central computer. Simplest and easiest form of LAN.
c. Ring topology - single cable that connects each workstation in a circle.
5. Network Architecture - specific arrangement of computers connected with various media
and following specific protocols.
a. Client-server - functionality of the server (designated for running a specific
application or applications) shared by the multiple clients. Servers are known as
hosts.
b. Peer-to-peer - a distributed system whose computers (nodes) participate in similar
roles, and therefore peers to each other. Decentralized system with no server.
c. Circuit switching - No shared routes, dedicated routes only
6. Communication Standards - different specifications exist to implement the various
network architectures.
a. TCP/IP - a suite of communication protocols that define how messages are created
and routed to destinations through the Internet. Creation and delivery.
b. WI-FI - the 803.11 standard, specifies how devices will connect to each other over
the air.
c. Bluetooth - defines how two Bluetooth enabled devices will communicate.
d. RFID (Radio Frequency Identification) - automatic identification method., relying
on storing and remotely retrieving data using devices called RFID tags or
transponders. *trackers
7. Connecting to a Network-
a. Dial-up lines - the client uses a modem connected to a computer and a telephone
line to dial into an Internet service provider’s (ISP) node to establish a modem-to-
modem link, which is then routed to the Internet.
b. Dedicated lines - a communications cable dedicated to a specific connection. It is
always on. Faster than dial up lines and less susceptible to external noise.
b.i. DSL - Digital Subscriber Line. Digital data transmission over the wires of
a local telephone network.
b.ii. Cable access - cable modems deliver broadband Internet access by taking
advantage of unused bandwidth on a cable television network.
Multiplexing.
c. Hub - device that provides a central point for cables in a network.
d. Switch - a networking device that directs packets to a specific hardware device
attached to a network.
e. Router - a computer networking device that buffers and forwards data packets
across networks toward their destinations through a process known as routing.
Also acts as a junction between two or more networks to buffer and transfer data
packets among them.
f. Multiplexer - device that selects one of many data-sources and outputs that source
into a single channel.
g. Gateway - entrance from one network to another network. Gateways transfer data
between private networks and the Internet. They also connect networks that use
different protocols.
