Computer NetworksComputer Networks

Comp302

Prepared by Iman GhasedianM.B.

Introduction :

• A computer network is a collection of

computers and devices connected to each

other. The network allows computers to

communicate with each other and share communicate with each other and share

resources and information.

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Network classification:

• Connection method

• Scale

• Functional relationship (network

architecture)architecture)

• Network topology

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Types of networks:

• Personal area network (PAN)

• Local area network (LAN)

• Campus area network (CAN)

• Metropolitan area network (MAN)• Metropolitan area network (MAN)

• Wide area network (WAN)

• Global area network (GAN)

• Virtual private network (VPN)

• Internetwork (Intranet,Extranet,Internet)

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Basic hardware components

• Network interface cards

• Repeaters

• Hubs

• Bridges • Bridges

• Switches

• Routers

• Wireless LAN access point

• Cables and Connectors

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Network interface cards

• A network card, network adapter or NIC

(network interface card) is a piece of

computer hardware designed to allow

computers to communicate over a computer computers to communicate over a computer

network.

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Repeaters

• A repeater is an electronic device that

receives a signal it at a higher power level, or

to the other side of an obstruction, so that the

signal can cover longer distances without

degradation. In most twisted pair Ethernet degradation. In most twisted pair Ethernet

configurations, repeaters are required for

cable which runs longer than 100 meters.

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Hubs

• A hub contains multiple ports. When a packet

arrives at one port, it is copied unmodified to

all ports of the hub for transmission. The

destination address in the frame is not changed

to a broadcast address. to a broadcast address.

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Bridges• A network bridge connects multiple network

segments at the data link layer (layer 2) of the OSL

model. Bridges do not promiscuously copy traffic to

all ports, as hubs do, but learn which MAC addresses

are reachable through specific ports. Once the bridge

associates a port and an address, it will send traffic associates a port and an address, it will send traffic

for that address only to that port. Bridges do send

broadcasts to all ports except the one on which the

broadcast was received.

• Bridges come in three basic types:

LAN, WAN, WLAN

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Switches

• A switch is a device that forwards and filters OSI layer 2 data grams between ports (connected cables) based on the MAC addresses in the packets. This is distinct from a hub in that it only forwards the packets to the ports involved in the communications rather than all ports connected. communications rather than all ports connected. Strictly speaking, a switch is not capable of routing traffic based on IP address (OSI Layer 3) which is necessary for communicating between network segments or within a large or complex LAN.

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Routers

• Routers are networking devices that forward

data packets between networks using headers

and forwarding tables to determine the best

path to forward the packets. Routers work at

the network layer.the network layer.

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Wireless LAN access point

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Category of Network Cables• Category 5 cable: Cat5 is capable of transmitting data

at speeds of up to 1000 Mbps (1 Gigabit per second).

• Category 6 cable: Cat6 cable was designed to perform at frequencies of up to 250 MHz and offers higher performance for better transmission of data higher performance for better transmission of data at speeds up to 1000 Mbps to 10Gbps.

• Category 7 cable: Cat7 cable designed to transmit data at 10-gigabit speeds and it is rated for transmission frequencies up to 600 MHz.

• Cat5,6 and 7 are terminated with RJ-45 conenectors.M.B.

RJ45 Connectors• RJ45 is a standard type of connector for

network cables. RJ45 connectors are most

commonly seen with Ethernet cables and

networks that they have eight pins to which

the wire strands of a cable interface the wire strands of a cable interface

electrically.

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Standard/Straight Cables

• Straight cables are used to connect PCs or other equipment to a HUB or Switch. If your connection is Pc to PC or HUB to HUB you MUST use a Crossed cable.

Standard, Straight-Through Wiring:

Pin No. strand color

• 1 white and green TX_D1+

2 green TX_D1-• 2 green TX_D1-

• 3 white and orange RX_D2+

• 4 blue BI_D3+

• 5 white and blue BI_D3-

• 6 orange RX_D2-

• 7 white and brown BI_D4+

• 8 brown BI_D4-M.B.

Crossed cable• Crossed cables are used to connect PCs to one

other PC or to connect a HUB to a HUB.

Cross Over wiring:

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Make a Network with two Computers

We can connect two computer together with or

without cable:

1- Connect with Cross cable

2- Connect with Wireless2- Connect with Wireless

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Hardware Component in a network

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Hardware Component in a network

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Benefits of Network

1- Resource sharing

Physical resources, such as printers, scanners & CD-ROM drives,

and Logical resources (software), such as databases and

applications.

2- Remote Access and File Transfer2- Remote Access and File Transfer

For example the ftp and telnet (remote login) commands.

3- Communications

Including: e-mail, chat and e-conferencing services.

4- Savings

All above services save money compared to other alternatives.

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Research:

Is there any disadvantage Is there any disadvantage of networking (in general)

? ? ?

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