CIS105

Networking: Computer Connections

Describe the basic components of a network.

Explain the methods of data transmission, including types of signals.

List communication equipment and channels options.

Describe various network topologies. Define firewall and communication

protocols.

2

A Computer Network is two or more computers connected together with data communications equipment over a communications channel/media.

Benefits of Networks? Reduce costs by sharing hardware, software,

and data (information). Communication!

3

4

Initiates instruction

Converts data

Signal path

Converts data

ReceivesInstruction

Modem – modulate /demodulate Converts digital signal to analog and vice versa

Telephone Dialup Modem (56 Kbps) DSL (Digital Subscriber Line) modem Cable Modems (cable companies) Cellular Modem (uses cellular system) Network Integrated w/ Motherboard Network Interface Card (NIC)

Installed in expansion slot Wired or wireless cards

5

Twisted Pair (TP) Cable Shielded (STP) Unshielded (UTP) Ethernet uses RJ45 Telephone uses RJ11 RJ – Registered Jack

Coaxial Cable (coax) Copper + 3 layers of insulation

Fiber Optic Cable Glass/plastic –

uses light to transmit Speed of light Tubes are insulated

Wireless (next slide)6

Physical Media

Wireless Generally slower Susceptible to interference Wi-Fi – Wireless Fidelity –

standard 802.11 MIMO (Multiple-in, Multiple-Out)

Infrared Bluetooth (see page 478) Cellular Radio

Microwave (line of site) Satellite – placed about

22,300 miles above 7

Wireless Media

Bandwidth – is the measurement of how much information can be transmitted over a medium over a prescribed period of time.

Signal Type Analog (continuous signal for older media). Digital (individual electrical pulses - binary).

Broadband transmission– multiple signals simultaneously in both directions - shared line - (Internet connections).

Baseband transmission – one signal at a time. Simplex – data is transmitted one direction only (TV). Half-duplex – data is transmitted in both directions,

but not at the same time (CB Radio, ATM, FAX). Full-duplex – data is transmitted in both directions at the

same time for same device (telephone, modem dial-up service).

8

Asynchronous – start/stop signals for each message. Message is usually one or two bytes long. Low-speed communication

Synchronous – larger block of characters are transmitted together. Includes error-check bits at the end of the

message. More complex and more expensive.

9

A LAN is a collection of computers connected together to share hardware, software, and data.

LAN Hardware Network Interface Cards (NIC) for devices Communications Channel / Media

Hub – connects computers to create a LAN

Bridges and Routers – connects LANS that use the same protocol

Gateways – connects LANS that use different protocols, and also serve as routers. 10

11

Node - each computer, printer, or server on network

Network Topology is the physical layout of a network.

Three common topologies Star Ring Bus See next slide

12

Ring Network

Star Network

Bus Network

Star Server is in center with attached clients If server goes down, network goes down Easy to expand Server controls collisions

Ring All computers connected by a single line If any computer goes down, the network goes down Difficult to expand No collisions, because token travels around one way

Bus All nodes share a single line If a computer goes down, the network is still up Easy to expand Many collisions – causes resend – Terminator’s located at

ends.13

Connecting two or more LAN’s of the same company. Can link computers across town or span the world. Common carriers are companies licensed by FCC to

provide these services as leased lines. Dedicated lines provides permanent connection

between two or more locations Companies can build their own (microwave, fiber,

etc.) T1 and T3 high-capacity digital lines can be leased Digital Subscriber Line (DSL) use telephone lines

Connect with Router or Gateway Will need a firewall to keep intruders out,

which can be hardware and/or software (see next slide).14

15

Firewalls block unauthorized users from entering the network and unauthorized software from making outbound connections (spyware).

Windows includes personal Firewall protection. Separate products can also be purchased.

16

GateWay

Internet

Client computer requests services from server.

Server returns requested information / data.

Common uses include Web Server, Print Server, File Server, and Email Server.

18

Connect directly to another computer to create a LAN.

Need to activate Operating System features.

Server is not required. All computers have equal status. Users share each other’s files,

printers, etc. Common in small offices.

19

How is all of this communication possible? Protocol - a set of rules for the exchange of data.

Agreement on how data is to be sent and receipt acknowledged.

Needed to allow computers from different vendors to communicate.

Common protocols include Ethernet, Wi-Fi, TCP/IP Transmission Control Protocol/Internet Protocol (TCP/IP)

Permits any computer to communicate over the Internet. Uses packet switching – original message is broken up;

each piece has address of destination; each piece may take a different route; receiving computer puts all the pieces together. 20

Want to learn more… CIS190 Introduction to LAN CNT140 Cisco Networking Basics MST150 Microsoft Windows Professional

HowStuffWorks-Firewalls

Review MCC’s Wireless Network: http://www.mc.maricopa.edu/its/net_services.html

21