SHAPE OF A NETWORK COPYRIGHT BTS

TOPOLOGY The way the computers are cabled together Four different layouts Logical topology describes the way data travels across the network COPYRIGHT BTS

FOUR TYPES Bus Network Star Network Ring Network Mesh COPYRIGHT BTS

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

COLLISION Data runs into each other Both nodes must back off and wait for line to be free Single bounce – caused by single 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 – usually only in BUS networks COPYRIGHT BTS

DISRUPTING COMMUNICATION Break in the cable Physically separated One end is disconnected All activity stops Computers can still function as stand-alone Just can’t communicate or share resources COPYRIGHT BTS

NETWORK EXPANSION 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 Continuous cable is preferable Repeater – used to connect two cables Boosts signal before it sends it on its way Better than connector because allows signal to travel further and still be correctly received COPYRIGHT BTS

ADVANTAGE/DISADVANTAGE Advantages Easy to implement and extend Well suited for temporary networks (quick setup) Initially less expensive than other topologies Cheap Disadvantages Difficult to administer/troubleshoot. Limited cable length and number of stations. If there is a problem with the cable, the entire network goes down. Performance degrades as additional computers are added or on heavy traffic. Low security (all computers on the bus can see all data transmissions). Proper termination is required.(loop must be in closed path). If many computers are attached, the amount of data flowing causes the network to slow down. COPYRIGHT BTS

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

ADVANTAGES/DISADVANTAGES Advantages Centralized resources and management Very expandable Nodes added easily Problems are easier to find Break in cable brings down only the node directly affected Disadvantages Requires great deal of cable If central point fails, everything shuts down More expensive to install COPYRIGHT BTS

RING NETWORK Nodes form a circle Data is quickly transferred without a ‘bottle neck’. (very fast, all data traffic is in the same direction) 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 COPYRIGHT BTS

TOKEN PASSING A way to avoid collisions and help data run smoothly Computers pass a small collection of bits – tokens 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 Token travels at speed of light – 186,000 miles per second COPYRIGHT BTS

ADVANTAGES/DISADVANTAGES Advantages Each node has equal opportunity to transmit Do not require a lot of cable or fancy equipment The transmission of data is relatively simple as packets travel in one direction only. Disadvantages Problems are difficult to find Total dependence upon the one cable Break in cabling brings down network COPYRIGHT BTS

MESH NETWORK Computer is connected to every other computer by separate cable or by wireless Uses mainly for Backbone networks COPYRIGHT BTS

ADVANTAGES/DISADVANTAGES Advantages Provides redundant or backup paths If one cable is broken, another takes over the traffic Easy to find problems Disadvantages Expensive to install because of all the cabling – Wireless connectivity can alleviate the cable cost but can be less reliable than cable and less bandwidth. COPYRIGHT BTS

SUMMARY OF NETWORK TOPOLOGIES COPYRIGHT BTS Topology Performance with few nodes or low network traffic Change in performance with many nodes or high network traffic Ease of troubleshooting (compared to other topologies) Cost of installation (compared to other topologies) Ease of setting up and modifying (compared to other topologies) Problems to the network caused by cable or node failure LINE (BUS) MediumMost affectedFairly easyLow Easy to set up and modify Failure of the bus cable causes total failure. Failure of a node has no affect. RING SlowLeast affectedHardHigh Easy to set up but harder to modify Cable or node failure causes total network failure. STAR Fast Some affect but the switch/hub can be upgraded easily EasyHigh Easy to set up and modify Cable or node failure only affects that node. Failure of the hub/switch or the server causes total network failure

ASSIGNMENT 1 List the 4 types of topologies: _____________ _______________ _________________ _________________ Which topology is probably the least expensive initially? __________________ This type network requires a hub or switch: _______________________ A _____________ network is the network behind the network for extreme bandwidths and high speed data. This type network would be the most reliable, but the most expensive to use if using wire or fiber, so mostly only used in backbone networks: ___________________ Collisions between data occur mostly in this type network, especially when the network grows to large: _______________________ All the nodes in this type network form a closed circle and pass tokens: ____________ These two types of network shapes are mainly used for backbone networks: _________________________ __________________________

ASSIGNMENT 2 Select the type of network you think based on the scenario: BUS / STAR / RING / MESH The node in this network failed, and brought down the entire network: __________ A cable was cut but only brought the one client down: ____________ The problem appears to be the switch, may need replaced: _________________ We are using wireless instead of wire, we’ll have tons of redundancy but will be to expensive to use wire: ___________________ A cable cut had brought down the entire network: __________________ It was easy to setup this network, but going to be hard to modify_____________ We’ve had to add 10 clients, now up to 20, the network speed is terrible:_____________ Adding a client is just connecting another wire into the switch: _______________

ASSIGNMENT 3 COPYRIGHT BTS NODE SWITCH NODE Given the scenario: Construct and draw a network diagram for: 5 Nodes Using the following symbols For each type network create a slide: Bus network / Star Network/ Ring Network So there will be a total of 3 networks, one on each slide. Example of a mesh network with the symbols given: