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Introduction to Network

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Computer Networks

Primary purposes of network is to increase productivity.

The minimum requirements for setting up a network are:An NIC cardNetwork MediaConnectors

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Network Interface Circuit (NIC) Card IS a printed circuit board that provides

network communication capabilities to and from a PC. Amplifies electronic signals Package data for transmission Physically connects computer to

transmission media Each NIC card is stored with a unique

address provided by IEEE called MAC address.

MAC is a 48 bit address, the first 24 bits is the vendor code and the next 24 bits represent the Serial Number.

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Network Media

IS the actual physical environment which data travels as it moves from one computer to another, and it connects network devices.

The most common types of network media are: Coaxial Cables Twisted Pair Cables Fiber Optic Cables Wireless

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Coaxial Cables

Consists of Single copper conductor Plastic insulation Over a wire mesh( Braided Copper Shielding) Another plastic insulation.

Used to connect dish antenna to a TV set. Coaxial Cables are of two types:

Thicknet (longest distance ) Thinnet

Connectors used: BNC T Terminators.

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Twisted Pair Cables

Used for both LANs and telephone systems. Composed of four color-coded pairs of

copper conductors twisted around each other.

The outer jacket provides protection and keeps the pairs in alignment.

There are two types: Unshielded Twisted Pair Cable (UTP) Shielded Twisted Pair Cable (STP)

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Twisted Pair CablesUnshielded Twisted Pair Cable (UTP)

Used in normal office environments. IS the most popular network media. Connectors used is RJ 45 connectors.

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Twisted Pair CablesUnshielded Twisted Pair Cable (UTP)

The advantage of UTP is its ability to limit signal degradation from electromagnetic interference (EMI) and Radio frequency interference.

Reduces Crosstalk There are different categories of UTP cable. The most used is CAT5 –have the

maximum segment length 100m.(shorter than coax)

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Twisted Pair CablesUnshielded Twisted Pair Cable (UTP)Implementation

Straight through Cable Used for

• Switch to router • Switch to PC or server • Hub to PC or server

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Twisted Pair CablesUnshielded Twisted Pair Cable (UTP)Implementation Crossover Cable (pins 1 and 2 on one connector connect to pins 3

and 6 on the other)

Used for• Switch to switch • Switch to hub • Hub to hub

• Router to router PC to PC

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Twisted Pair CablesUnshielded Twisted Pair Cable (UTP)Implementation

Roll-over Cable (pins 1 on one connector connect to pins 8 on the

other)

Used for• Console port of a router or switch to the PC

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Twisted Pair Cablesshielded Twisted Pair Cable (STP)

Protect against signal degradation. Each pair of wires is wrapped in a metallic foil. The four pairs of wires are then wrapped in an

overall metallic braid or foil.

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Twisted Pair Cablesshielded Twisted Pair Cable (STP)

Reduces electrical noise within and outside the cable.

Used in Token Ring. Maximum segment length is 100m

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Fiber Optic Cables

Capable of conducting modulated light transmission.

Consists of two fibers encased in separate sheaths.

• A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity.

Connectors used are multimode. Not effected by EMI

There are two types of fiber-optic cables: Single-mode Multimode

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Fiber Optic Cables Single-mode

Allow only one mode of light to propagate through the fiber.

Capable of higher bandwidth and greater distances

Uses Lasers as the light-generation method and is expensive.

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Fiber Optic Cables Multimode

Allows multiple modes of light to propagate through the fiber.

Often used for workgroup applications.

The segment length is less than the single-mode.

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Wireless

The device use to signal distribution called wireless hub or access point

To receive the signal from the access point the pc needs to install wireless (NIC)

Radio frequency (RF)• Transmit voice, video and data• Affected by electromagnetic interference• Limited distance

Wireless LAN (WLAN) use radio waves, microwave and Infrared waves.

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Network Topologies

The configurations of network components Widely used network topologies

BusStarExtended starRingMeshPartial Mesh

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Bus Network Topology

Most simple network topology All devices connected to a common central

cable (wire or other media ) Inexpensive Easily expanded If cable fails, the entire network will shut down Earlier Ethernet commonly implement a bus

topology

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Bus Network Topology (Continued)

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Star Network Topology

Star topology is centered around central routing device called a switch or a hub by point-to-point links.

All network nodes connect to the hub Easy to install and update If hub fails, network fails Disadvantage that it require more cabling

therefore, higher cost than the bus. Extended star

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Ring Network Topology

Each node connected to two other nodes in a ring

Similar to the buss, but with the ends of the buss connected together by unidirectional transmission link to form a single closed loop.

Each station on the network connects to the network at a repeater.

Expensive and difficult to install One example of a ring topology is Token Ring

networks

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Ring Network Topology (Continued)

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Dual-Ring Tow rings allow data to be sent in both

directionsCreates redundancy.

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Mesh Network Topology

Every node connected to every other node Fast Reliable

No hub or bus to failIf one device goes down, it is the only node affected

ExpensiveEvery node must be wired to every other node

Difficult to add nodesIf there are 32 nodes in a mesh network and you

wish to add a new node, how many new cables must you add?

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Partial MeshAt least one derive is connected to all

other devices without being fully meshed.

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