Networking

Chap:02Topologies

1.2

1.3 Data Flow (Modes of Communication)1.3 Data Flow (Modes of Communication)

•Simplex: Simplex: in simplex mode communication is in simplex mode communication is unidirectional. Only one device on a link unidirectional. Only one device on a link can send the data. The other device will can send the data. The other device will only receive the data. E.g Keyboard & only receive the data. E.g Keyboard & MonitorMonitor

•Half Duplex: Half Duplex: in this mode both sender and receiver in this mode both sender and receiver can send and receive, but not at the same can send and receive, but not at the same time. At a time one is sender the other act time. At a time one is sender the other act as receiver. E.g Walki-talkiesas receiver. E.g Walki-talkies

1.3

Conti...Conti...

•Full Duplex: Full Duplex: in this mode both sender and in this mode both sender and receiver can send and receive at the receiver can send and receive at the same time. E.g telephonesame time. E.g telephone

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Topology:Topology:

•The Physical structure of the network is known as Topology.

•The Physical layout of the links and devices is called topology.

1.5

Figure 1.4 Four basic Categories of topology

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Bus Topology:Bus Topology:

•All devices are directly connected to a single main cable

•Main cable act as the backbone for the network•Computer are connected with the main cable via

local loop/drop line•Only one device can send the data at a time

•Otherwise collision will occur.•Terminator are used at the end of the main cable

•Main cable is used either thick net/ thick net.

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Figure 1.7 A bus topology connecting three stations

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Bus Topology

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Advantages Use of cable is economicalMedia is inexpensive and easy to work withSystem is simple and reliable .Bus is easy to extendDisadvantages of Bus Topology:Network can slow down in heavy traffic Problems are difficult to isolateCable break can affect many users

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Star Topology:Star Topology:

•In a star topology, each device/computers has a direct point-to-point link only to a central

controller•central controller is called a hub/switch

•The devices/computers are not directly linked to one another.

•If one device wants to send data toanother, it sends the data to the controller,•Controller then send the data to the other

connected Device/computers

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Figure 1.6 A star topology connecting four stations

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Star Topology

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Star Topology

Advantages of Star Topology

Modifying system and adding new computers is easy . Centralized monitoring and management are possible Failure of one computer does not affect the rest of the network

Disadvantages of Star Topology : If the centralized point fails, the

network fails

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Ring Topology:Ring Topology:

•In a Ring topology, each device has a dedicated point-to-point connection with only

the two devices on either side of it.

• A signal is passed in ring in one direction, from device to device, until it reaches its

destination.

• token (frame) is circulating in the ring

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Ring Topology:Ring Topology:

•Each device wait for its number to send the data

•At a time only one device can send the data

•Each device in the ring contain a repeater.

Note: Repeater is used to Re-generate the weaken signals

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Figure 1.8 A ring topology connecting six stations

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Advantages of Ring Topology

System provides equal access for all computers Performance is even despite many usersDisadvantages of Ring Topology:Failure of one computer can impact the rest of the networkProblems are hard to isolate.

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Ring Topology

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Mesh Topology:Mesh Topology:

•In a mesh topology, every device has a dedicated point-to-point link to every

other device in the Network

•If a network contain ‘N’ number of computers then each computer needs ‘N-1’ number of

Input/output ports

•The link between devices usually are Full duplex

• very reliable topology (if one link goes down then other line is available)

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Figure 1.5 A fully connected mesh topology (five devices)

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Mesh Topology

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•End of Chapter