Roshan BasnetStudent id: 3069391.Network topology is a systematic arrangement of computers and its elements, including its nodes andconnecting lines.2. The two classifications of network topology are:a.Physical topology : The mapping of the nodes of a network and the physical connections betweenthem – i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between thenodes and the cabling or wiring system.b. Logical Topology : is also called as Signal Topology.It is a network computing term used to describethe arrangement of devices on a network and how they communicate with one another.Logical topologies are bound to network protocols and describe how data is moved across the network3. Four most common topologies used in industry are:Bus topologyRing topology.Star topology.Tree topologya) Bus topology: In this topology each computer or server is connected to the single bus cablethrough some kind of connector.Advantage:1. low wiring complexity.2. Economical and easy to manage.Disadvantage:1. Limited Network.2. A cable end which is not correctly terminated can make the entire bus inoperative, especiallywith a high transmission speed.
b) Ring Topology: In this topology each computer is connected to the network in a ring and eachcomputer has a unique address which is used for identification purposes. The signal passesthrough each computer connected to the ring in one direction.Advantage:Very orderly network where every device has access to the token and the opportunity totransmitPerforms better than a star topology under heavy network loadCan create much larger network using Token Ring.Does not require network server to manage the connectivity between the computersDisadvantage:One malfunctioning workstation or bad port in the MAU can create problems for theentire networkMoves, adds and changes of devices can affect the networkNetwork adapter cards and MAUs are much more expensive than Ethernet cards andhubsMuch slower than an Ethernet network under normal loadc) Star Topology: In a star topology all computers are connected to a central hub, which controlsthe network communications, and can communicate with other hubs. Range limits are about100 meters from the hub.AdvantagesGood performanceReliable (if one connection fails, it doesnt affect others)Easy to replace, install or remove hosts or other devicesDisadvantagesExpensive to installHub
Extra hardware requiredd) Tree Topology: This network topology is also referred as hierarchical network. In thistopology central root node (the top level) is connected to more other nodes that are onlower level in the hierarchy with a point-to-point link between each of the second levelnodes and the top level central root node, while each of the second level nodes that areconnected to the top level central root node will also have one or more other nodes thatare one level lower in the hierarchy (i.e., the third level) connected to it.Advantages :Point-to-point wiring for individual segments.Supported by several hardware and software companies.Disadvantage:More complicated network.Expensive.3. Hybrid Topology: It is a combination of any two or more network topologies. A hybrid topologyalways accrues when two different basic network topologies are connected.1stlevel2ndlevelhub hub
Advantage:It allows coexistence and cohabitation by integrating different network technology to work together.Disadvantage: It is very expensive.Needs frequent support to maintain them.5.Two common type of hybrid Topology are:• A Star ring network : The Star Ring is a combination of ring and star topologies. The hubs in a starring are connected in a star pattern by the main hub.This network consists of two or more star topologies connected using a multistation access unit(MAU) as a centralized hub.• A Star Bus network : This networking topology uses hubs for workgroups or departmentallocal area networks (LANs) which is connected by using a network bus to form a single network. Star bustopology is a combination of star topology superimposed on a backbone bus topology.It consists of two or more star topologies connected using a bus trunk (the bus trunk serves as thenetworks backbone).6)Some organization uses hybrid topology rather than the normal topology because of the followingreasons:
a) use a combination of any two or more topologies in such a way that the resulting networkdoes not exhibit one of the standard topologiesb) Hybrid topology allows coexistence and cohabitation by integrating different networktechnology to work together.c) Better functionality.7)Some topology requires end points to be terminated because Without termination, when thesignal reaches the end of the wire, it bounces back and travels back up the wire. When a signalechoes back and forth along an unterminated bus, it is called ringing. To stop the signals fromringing, terminators are attached at either end of the segment. The terminators absorb theelectrical energy and stop the reflections.8) In a ring topology the funtion of Token is to transmit attached data from source to destinationcomputer. Token frame is repeated from station to station until arriving at a station that needs totransmit data. When a station needs to transmit data, it converts the token frame into a data framefor transmission. Once the sending station receives its own data frame, it converts the frame backinto a token. If a transmission error occurs and no token frame, or more than one, is present, aspecial station referred to as the Active Monitor detects the problem and removes and/or reinsertstokens as necessary9) Being a Network Designer I would suggest to go with Star Bus Topology because of easy use,easy to monitor the network , security and cost effectiveness..