Topology

bus topology a linear bus topology consists of a main run of cable with a terminator at each end (see fig. 1). all nodes (file server, workstations, and peripherals) are connected to the linear cable. ethernet networks use a linear bus topology. in this topology network messages are sent to each terminal on the network - so if one of the terminals breaks then the others are not affected. if you want to send a message from computer a to computer b then all the computers will receive the message, however because you have included computer b's address, only computer b will pick it up and display it.

advantages of a linear bus topology easy to connect a computer or peripheral to a linear bus. requires less cable length than a star topology. easy to implement and extend well suited for temporary networks that must be set up in a hurry typically the least cheapest topology to implement failure of one station does not affect others

disadvantages of a linear bus topology entire network shuts down if there is a break in the main cable. terminators are required at both ends of the backbone cable. difficult to identify the problem if the entire network shuts down. not meant to be used as a stand-alone solution in a large building difficult to administer/troubleshoot limited cable length and number of stations 1

a cable break can disable the entire network; no redundancy maintenance costs may be higher in the long run performance degrades as additional computers are added

star topology a star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub . data on a star network passes through the hub or concentrator before continuing to its destination. the hub manages and controls all functions of the network. it also acts as a repeater for the data flow. this configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.

advantages of a star topology easy to install and wire. no disruptions to the network then connecting or removing devices. easy to detect faults and to remove parts. easy to add new stations easy to monitor and troubleshoot can accommodate different wiring easy to add devices as the network expands one cable failure does not bring down the entire network (resilience) hub provides centralised management easy to find device and cable problems

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can be upgraded to faster speeds lots of support as it is the most used

disadvantages of a star topology requires more cable length than a linear topology. if the hub fails, nodes attached are disabled. more expensive than linear bus topologies because of the cost of the hub. more cable required

ring topology a ring topology consists of a set of stations connected serially by cable. in other words, it’s a circle or ring of computers. there are no terminated ends to the cable; the signal travels around the circle in a clockwise direction. note that while this topology functions logically as ring, it is physically wired as a star. each station on the ring has equal access but only one station can talk at a time. in contrast to the ‘passive’ topology of the bus, the ring employs an ‘active’ topology. each station repeats or ’boosts’ the signal before passing it on to the next station. rings are normally implemented using twisted pair or fiber-optic cable.

advantages of ring topology: growth of system has minimal impact on performance

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all stations have equal access data packets travel at great speed no collisions easier to fault find no terminators required

disadvantages of ring topology: most expensive topology failure of one computer may impact others complex requires more cable than a bus a break in the ring will bring it down not as common as the bus – less devices available

mesh topology a type of network setup where each of the computers and network devices are interconnected with one another, allowing for most transmissions to be distributed, even if one of the connections go down. this type of topology is not commonly used for most computer networks as it is difficult and expensive to have redundant connection to every computer. however, this type of topology is commonly used for wireless networks. below is a visual example of a simple computer setup on a network using a mesh topology.

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not common on lans most often used in wans to interconnect lans each node is connected to every other node allows communication to continue in the event of a break in any one connection it is “fault tolerant”

advantages improves fault tolerance if any cable fails, there are many other ways for two nodes to communicate that communication can take place directly between any two nodes without an intermediary there are multiple routes between any two points

disadvantages expensive difficult to install difficult to manage difficult to troubleshoot

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