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Dammam Community College

Network Overview

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Advantages of networks

• Enable sharing of files

• Enables sharing of resources

• It saves time

• Internet access

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What is a Network ?

• Two or more computers connected together by a cable.

• LAN - Local Area Network

• MAN - Metropolitan Area Network

• WAN - Wide Area Network

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Basic Network Components

• Network Interface Cards - NIC• Network cabling & connections• Servers & Workstations• Network Operating System – NOS

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Extending a LAN

• Repeaters

• Bridges

• Routers

• Gateways

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Network Interface Card

• Interrupt (IRQ) request line

• Base I/O port address

• Base memory address

• Direct memory access (DMA) request line

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Basic Types of LAN’s

• Peer-to-Peer: Two computers participating equally in the network.

• Server Based: Security and other network functions are provided by a dedicated server.

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Network Elements

• Sending Computer

• Receiving Computer

• Protocol

• Media - Wire or Wireless

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Network Protocols • A protocol is a set of rules that govern network

communication.• A protocol suite is a group of protocols that can be

used together.• The standard protocols are

– Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX)

– Networked Basic Input/Output System/NetBIOS Enhanced User Interface (NetBEUI)

– Transmission Control Protocol/Internet Protocol (TCP/IP)– AppleTalk– Data Link Control (DLC)

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Protocols Summary

Protocols - A set of rules for a network Examples:

– TCP/IP– TELNET– IPX/SPX– NET BEUI

To cater for the following types of networking technology:

Ethernet

Fast Ethernet

Token Ring

FDDI

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Main Types of Cable

• Coaxial Cable

• Twisted Pair

• Fiber Optic

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Network Cabling

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Three different types of network cabling and their advantages are:

1. Twisted pair cable is readily available, easy to install and inexpensive

2. Coaxial cable is standard technology that resists rough treatment and EMI, can transmit over longer distance than twisted pair

3.Fibre Optic cable is immune to EMI and detection outside and provides reliable and secure media with high bandwidth

Cabling types and advantages

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Types of Cable Connectors

• BNC Connector

• RJ-45 Connector

• Duplex SC Connector

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Ethernet Cable Summary

Specification Cable Type Maximum length

10BaseTUnshielded Twisted Pair 100 meters

10Base2 Thin Coaxial 185 meters

10Base5 Thick Coaxial 500 meters

10BaseFFiber Optic 2000 meters

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LAN Communication

• Ethernet uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as well as bus topology.

• Token ring allows only the station holding the token to transmit data.

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LAN Topology

Topology is the way the network is connected physically. Following are topologies:

• Bus Topology

• Ring Topology

• Star Topology

• Mesh Topology

• Hybrid Topology

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BUS TOPOLOGY

WORKSTATION 1 WORKSTATION 2 WORKSTATION 3 SERVERPRINTER

T-CONNECTOR TERMINATOR

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Workstation 1Workstation 2

Workstation 3

Workstation 4

Workstation 5

server

printer

RINGTOPOLOGY

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HUB

WORKSTATION 1

WORKSTATION 2

WORKSTATION 3WORKSTATION 4WORKSTATION 5

WORKSTATION 6

SERVERPRINTER

PRINTER

STAR TOPOLOGY

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Workstation 1Workstation 2

Workstation 3

Workstation 4

Workstation 5

server

printer

MESHTOPOLOGY

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HYBRID TOPOLOGY

Workstation 1Workstation 2

Workstation 3

Workstation 4

Workstation 5

server

printer

RINGTOPOLOGY

HUB

WORKSTATION 1

WORKSTATION 2

WORKSTATION 3WORKSTATION 4WORKSTATION 5

WORKSTATION 6

SERVERPRINTER

PRINTER

STAR TOPOLOGY

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Networking Essentials

• Local Area Network (LAN)– Usually limited to short distances– Owned by the organization that uses it– Usually employs solid cable– Transmission rates tend to be high in the

range of 1Mbps to 100Mbps

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Networking Essentials

Local Area Network

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Networking Essentials

• Wide Area Network (WAN)– Usually owned by major telephone companies– Cover extremely large areas– Most common WAN protocol is TCP/IP

(common for internet)– Transmission rates are usually slower than

LAN or MAN rates (2400bps to 128Kbps)– Technology such as ATM is improving data

transmission rates

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Networking Essentials

Wide Area Network

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Networking Essentials

• Network Components– Network Interface Card (NIC)

• Usually found in the form of an expansion card• Can have multiple connector types• Can be integrated into the motherboard• Can be 8-bit, 16-bit ISA, VLBus or PCI• Is used to connect the computer or PC to the

network

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Networking Essentials

• Network Components (cont.)– Network cable

• Coaxial cable– Thinnet (10Base-2) and Thicknet (10Base-5)– RG-59 used in broadband networks to support video and

data

• Twisted pair– Is used by dial-up modems for dial up connection to the

internet– Unshielded and Shielded twisted pair (UTP and STP)– Category 1 to 5

• Fiber optic

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Networking Essentials

• Network Protocols– TCP/IP

• Transmission Control Protocol/Internet Protocol• The most widely used protocol suite in the world• Most major NOSs support the use of TCP/IP• Originally designed for WAN use• Routable protocol that offers true internetworking

and interoperability between disparate NOSs

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Common Topologies

• Bus Topology– Computers in the network are connected to a single

cable– Main cable is called the backbone– Signals from computers travel in both directions– Cable must be properly terminated at both ends– Only a single computer can transmit a signal at any

given time

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Common Topologies

Bus Topology

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Common Topologies

• Bus Topology– Advantages

• Easy to apply and maintain• Requires minimal amount of cabling• Easy to extend by adding cable or adding

repeaters• Can be extended with the addition of hubs

connected to the bus

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Common Topologies

• Bus Topology– Disadvantages

• The speed of the network is directly related to the number of computers connected to the bus

• Damage to the cable at any location may bring down the entire network

• The network usually has to be taken down to add additional computers

• It may be difficult to locate a break or short in the cable without specialized equipment

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Common Topologies

• Star Topology– All computers are connected to a central

device called a hub– Each signal is initially sent to the central hub

and then either out to all computers (broadcast star network) or to the recipient computer (switched star network)

– Several star networks can be linked together

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Common TopologiesStar Topology

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Common Topologies

• Star Topology– Advantages

• Easy to expand• If one computer fails or one cable connecting a

computer fails, the rest of the network stays up• Hubs can support different types of cable• UTP is the least expensive type of cable

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Common Topologies

• Star Topology– Disadvantages

• Failure of the central hub results in failure of the entire network

• Separate cables are required to connect each workstation to a hub

• The initial cost of the equipment is more than with a straight bus topology due to the added expense of the hubs and running separate cables to each computer

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Common Topologies

• Ring Topology– All computers in the network are joined in a logical

ring– The actual appearance may look like the star topology– The central network device, called an MAU, has a

loop inside of it, which creates the ring– utilises token-ring to transmit data around the

network. If a token is free of data a transmitting computer grabs it to send data by it and on the receiving end the data is removed and free token passed on to the network

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Common Topologies

• Ring Topology– Advantages

• Ring networks handle collisions more efficiently than bus networks

• No single computer can end up using the network all the time. This is theoretically possible in the bus topology.

• It is faster than the star topology• Can be very long because each computer

reinforces the message

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Common Topologies

• Ring Topology– Disadvantages

• On a physical ring network, you must down the entire network to add or remove computers

• On a physical ring network, if a computer goes down the entire network may go down

• It may not be easy to locate a faulty computer or device on the physical ring network

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Common Topologies

Ring Topology

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Connectivity Within Networks

• Hubs– Hubs can be used to connect networks but

are more commonly used to extend a network– Most hubs will simply rebroadcast signals to

all ports– Intelligent hubs rebroadcast signals only to

the actual destination port

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Connectivity Within Networks

• Repeaters– Amplify signals on networks– Most commonly used to increase the length of

the network backbone– Normally signals should not pass through

more than two repeaters before reaching their destination

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Connectivity Within Networks

• Bridges– Selectively sends signals from one segment to the

other– Can filter signals based on the protocol type– Transparent bridges contain the addresses of each

computer and calculate the shortest route to the destination computer

– Source-routing bridges—sender determines the proper route

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Connectivity Between Networks

• Routers– Connect independent networks– Dynamic and static routers– Distance-vector routing

• Each router sends its table to all other routers at regular intervals

– Link-state routing• Instead of sending the entire table, only the

changes are sent

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Connectivity Between Networks•Gateways

• Provides all the connectivity, and even greater functionality of routers and bridges• usually resides on a dedicated computer and acts as a translator between two completely dissimilar systems or applications• Are slower than bridges or routers• Also provide access to special services such as e-mail or fax functions

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Maintaining and Troubleshooting Networks

• Reduced bandwidth

• Loss of data• Slow loading of

programs and files• Unauthorized

software

• Traffic overloads

• Common mode failures

• Network security violations

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•A network provides connections, communications, and services.•Networks are either peer-to-peer or server-based. •Network topology types are star, bus, and ring.•A NIC connects the computer to the network.•Network cable types are twisted-pair, coaxial, and fiberoptic.•A network protocol provides the rules for network communications.•Networks can be extended with repeaters, bridges, routers, and gateways.

Summary