computer networks workshop

Abdullah [email protected]

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Computer Networking

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INFORMATION TECHNOLOGY – Part II5. Introduction to Networking

Who R We?? دماغهم شباب فدماغك بتجيىف اللى نفساألفكار

االجازه فى

Why We do that ? ... .. اكتب.. .. فيديو اشرح شير ترجم ... أعلن

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Index:

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Computer Networks :• Group of interconnected computers

• First Network : The Advanced Research Projects Agency (ARPA) funded the design of the "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense

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Importance of Networks:

• Sharing information • Do you prefer these?

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• Or this?

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• Sharing hardware or software

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• E.g. print document

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• Centralize administration and support• E.g. Internet-based, so everyone can access the same

administrative or support application from their PCs

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5.5. Network Types… Network Types…Size…Management…TopologySize…Management…Topology

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Network Classification : 1

• By Size or Scale– LAN– WAN– MAN– CAN– PAN

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Local Area Network (LAN)

• Contains printers, servers and computers• Contained in one office or building• Organizations often have several LANS• Small network, short distance

• Limited by no. of computers and distance covered• Serve a department within an organization

• Examples: • Network inside the Student Computer Room• Network inside your home

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• Wide Area Network (WAN)• Two or more LANs connected Over a large

geographic area• Typically use public, leased lines phone lines

• Examples:• Internet

WAN

Student Computer Centre

Your home

USA

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• Example WAN technologies:

• ISDN – Integrated Service Digital Network• Basic rate: 192 Kbps Primary rate: 1.544Mbps

• ATM – Asynchronous Transfer Mode• Support B-ISDN: 155Mbps or 622Mbps or higher

Large network that connects different organizations

Shares regional resources

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Metropolitan Area Network (MAN)

A LAN in one large geographic area

Resources related to the same organization

Each department shares the LAN

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Campus Area Networks (CAN)

Very small scale network

Range is less than 2 meters

Cell phones, connectify :D

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Personal Area Network (PAN)

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• By Structure / Functional / Management Relationship :

1- Peer to Peer. 2- Client / Server.

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Peer-to-Peer Networks• Peer-to-peer network is also called workgroup• No hierarchy among computers all are equal• No administrator responsible for the network

Peer-to-peer

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• Advantages of peer-to-peer networks:• Low cost• Simple to configure• User has full accessibility of the computer

• Disadvantages of peer-to-peer networks:• May have duplication in resources• Difficult to uphold security policy• Difficult to handle uneven loading

• Where peer-to-peer network is appropriate:• 10 or less users• No specialized services required• Security is not an issue• Only limited growth in the foreseeable future

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Clients and Servers• Network ClientsClients (WorkstationWorkstation)

• Computers that request network resources or services

• Network ServersServers• Computers that manage and provide network resources and

services to clients • Access to data controlled by server• Server is the most important computer

• Usually have more processing power, memory and hard disk space than clients

• Run Network Operating System that can manage not only data, but also users, groups, security, and applications on the network

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• Advantages of client/server networks• Facilitate resource sharing – centrally administrate and

control• Facilitate system backup and improve fault tolerance• Enhance security – only administrator can have access

to Server• Support more users – difficult to achieve with peer-to-

peer networks

• Disadvantages of client/server networks• High cost for Servers• Need expert to configure the network• Introduce a single point of failure to the system

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By Topology / Physical Connectivity

– BUS– STAR– RING– MESH– TREE

Network Topology– Logical layout of wires

and equipment– Choice affects

Network performance Network size Network collision detection

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Topology ― 3 basic types• How so many computers are connected together?

Bus Topology Ring Topology

Star Topology

Hub

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• Bus Topology (Linear) • Simple and low-cost الدش توصيلة• A single cable called a trunk (backbone, segment)

connects all nodes• Only one computer can send messages at a time• Terminator ends the wires

Advantages

Easy to setupSmall amount of wire

DisadvantagesSlowEasy to crash

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Star Topology: (Centralized Device)Most common topology• Each computer has a cable

connected to a single point• More cabling, hence higher cost• All signals transmission through the hub; if down, entire network down• All nodes connect to a hub….Packets sent to hub…Hub sends packet to destination

Advantages :

Easy to setup

One cable can not crash network

Disadvantages

One hub crashing downs entire network

Uses lots of cable

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How to construct a network with Bus / Star Topology?

Star Topology

Bus Topology

BNC T-Connector

Coaxial cable

Network Card

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• Ring Topology :( الخارجيه (مبنى• Every computer serves as

a repeater to boost signals• Typical way to send data:

• Token passing• only the computer who

gets the token can send

data• Disadvantages

• Difficult to add computers• More expensive• If one computer fails, whole network fails

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MESH

• All computers connected together

• Internet is a mesh network

• Advantage– Data will always be

delivered• Disadvantages

– Lots of cable– Hard to setup

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TREE

• Hierarchal Model

• Advantages– Scalable– Easy Implementation– Easy Troubleshooting

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Traaaaaaaaacks

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Vendors :

• http://www.cisco.com/• http://www.nortel-us.com/• http://www.avaya.com/usa/• http://www.juniper.net/• http://www8.hp.com/us/en/home.html

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• Links that connect nodes with certain Speed, Security, and Size

• Two main categories:– Guided ― wires, cables– Unguided ― wireless transmission, e.g. radio,

microwave, infrared, sound, sonar

• We will concentrate on guided media first:– Twisted-Pair cables:

Unshielded Twisted-Pair (UTP) cables Shielded Twisted-Pair (STP) cables

– Coaxial cables– Fiber-optic cables

Transmission Media

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• If the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors.

• Most common LAN cable• Called Cat5 or 100BaseT• Four pairs of copper cable twisted• May be shielded from interference• Speeds range from

1 Mbps to 1,000 Mbps

Twisted-Pair Cables

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Unshielded Twisted-Pair (UTP)

• Typically wrapped inside a plastic cover (for mechanical protection)

• A sample UTP cable with 5 unshielded twisted pairs of wires

MetalInsulator

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Shielded Twisted-Pair (STP)• STP cables are similar to UTP cables, except there

is a metal foil or braided-metal-mesh cover that encases each pair of insulated wires

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Coaxial Cables• In general, coaxial cables, or coax,• Similar to cable TV wire• One wire runs through cable• Shielded from interference• Speeds up to 10 Mbps

• Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit

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Fiber-Optic Cables

• Data is transmitted with light pulses• Glass strand instead of cable• Immune to interference• Very secure• Hard to work with• Speeds up to

100 Gbps

• Beyond the critical angle total internal reflection

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Advantages and Disadvantages Noise resistance ― external light is blocked by outer

jacket Less signal attenuation ― a signal can run for miles

without regeneration (currently, the lowest measured loss is about ~4% or 0.16dB per km)

Higher bandwidth ― currently, limits on data rates come from the signal generation/reception technology, not the fiber itself

Cost ― Optical fibers are expensive Installation/maintenance

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Wireless Media:

• Data transmitted through the air• LANs use radio waves• WANs use microwave signals• Easy to setup• Difficult to secure• Examples: Wi-Fi

Wi-MAX VSAT

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Communication Model

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Communication Model

• Source– generates data to be transmitted

• Transmitter– Converts data into transmittable signals

• Media– Carries data

• Receiver– Converts received signal into data

• Destination– Takes incoming data

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Transmission Modes

• Simplex– One direction

e.g. Television

• Half duplex– Either direction, but

only one way at a time e.g. police radio

• Full duplex– Both directions at the

same time e.g. telephone

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Communication Types

• Unicasting (one-to-one)

• Multicasting (one-to-many)

• Broadcasting (one-to-all)

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• /Unified and Integration Inside

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computer networks workshop

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