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Shape of a Network. Topology The way the computers are cabled together The way the computers are cabled together Four different layouts Four different.

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Presentation on theme: "Shape of a Network. Topology The way the computers are cabled together The way the computers are cabled together Four different layouts Four different."— Presentation transcript:

1 Shape of a Network

2 Topology The way the computers are cabled together The way the computers are cabled together Four different layouts Four different layouts Logical topology describes the way data travels across the network Logical topology describes the way data travels across the network

3 Four types Bus Network Bus Network Star Network Star Network Ring Network Ring Network Mesh Mesh

4 Bus Network Simplest/easiest Simplest/easiest Linear Linear Single cable – trunk Single cable – trunk Computers are passive participants Computers are passive participants Any computer (node) can pass a message Any computer (node) can pass a message Transmissions are limited to one computer at a time – one computer is the master Transmissions are limited to one computer at a time – one computer is the master Other computers must wait until the line is free Other computers must wait until the line is free

5 Collision Data runs into each other Data runs into each other CSMA/CD – carrier sense multiple accesses with collision detection CSMA/CD – carrier sense multiple accesses with collision detection Both nodes must back off and wait for line to be free Both nodes must back off and wait for line to be free Signal bounce – caused by signal that continues uninterrupted to the end of the bus and then keeps bouncing back and forth along the cable, keeping other nodes from using the line Signal bounce – caused by signal that continues uninterrupted to the end of the bus and then keeps bouncing back and forth along the cable, keeping other nodes from using the line Terminator – absorbs signals and keeps them from bouncing back along the trunk Terminator – absorbs signals and keeps them from bouncing back along the trunk

6 Disrupting Communication Break in the cable Break in the cable –Physically separated –One end is disconnected All activity stops All activity stops Computers can still function as stand-alone Computers can still function as stand-alone –Just cant communicate or share resources

7 Network Expansion Cable in a bus network can be expanded in one of two ways: Cable in a bus network can be expanded in one of two ways: –Barrel connector – connects two pieces of cable to make longer Connectors weaken signal Connectors weaken signal Continuous cable is preferable Continuous cable is preferable –Repeater – used to connect two cables Boosts signal before it sends it on its way Boosts signal before it sends it on its way Better than connector because allows signal to travel further and still be correctly received Better than connector because allows signal to travel further and still be correctly received

8 Advantage/Disadvantage Advantages Advantages –Easy to implement –Require less cable –Nodes relatively easy to add and remove Disadvantages Disadvantages –Problems more difficult to pinpoint –Breaks mean a breakdown in entire network –Too many nodes slow network

9 Star Network Like arms of octopus Like arms of octopus Stretches out in different directions Stretches out in different directions Hub – device in the middle Hub – device in the middle Hub – connects nodes in the arms Hub – connects nodes in the arms Hub participates actively in the network boosting signals as they pass Hub participates actively in the network boosting signals as they pass It can be a passive wiring panel that simply relays transmission through the network It can be a passive wiring panel that simply relays transmission through the network

10 Advantages/Disadvantages Advantages Advantages –Centralized resources and management –Expandable –Nodes added easily –Problems are easier to find –Break in cable brings down only the node directly affected Disadvantages Disadvantages –Requires great deal of cable –If central point fails, everything shuts down

11 Ring Network Nodes form a circle Nodes form a circle Data travels from node to node Data travels from node to node Each node communicates with only two others: Each node communicates with only two others: –The one that transmits to it –The one to which it transmits The failure of one node can bring down the whole system The failure of one node can bring down the whole system

12 Token Passing A way to avoid collisions and help data run smoothly A way to avoid collisions and help data run smoothly Computers pass a small collection of bits – tokens Computers pass a small collection of bits – tokens A node has to wait until it has a token to transmit data A node has to wait until it has a token to transmit data Computer then modifies token to let other nodes know that a token is in use Computer then modifies token to let other nodes know that a token is in use Token travels at speed of light – 186,000 miles per second Token travels at speed of light – 186,000 miles per second

13 Advantages/Disadvantages Advantages Advantages –Each node has equal opportunity to transmit –Do not require a lot of cable or fancy equipment Disadvantages Disadvantages –Problems are difficult to find –Break in cabling brings down network

14 Mesh Network Computer is connected to every other computer by separate cable Computer is connected to every other computer by separate cable

15 Advantages/Disadvantages Advantages Advantages –Provides redundant or backup paths –If one cable is broken, another takes over the traffic –Easy to find problems Disadvantages Disadvantages –Expensive to install because of all the cabling


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