Network TopologiesBy:Nawaraj Kumar Mahato&Bayo Ken Munduni
Network Topologies Network topology is the arrangement of the various elements(links, nodes, etc.) of a computer network. Essentially, it is thetopological structure of a network, and may be depicted physically orlogically. Physical topology refers to the placement of the networks variouscomponents, including device location and cable installation. Logical topology shows how data flows within a network, regardless of itsphysical design. Distances between nodes, physical interconnections,transmission rates, and/or signal types may differ between two networks,yet their topologies may be identical.
Point-to-point The simplest topology is a permanent link between two endpoints.Switched point-to-point topologies are the basic model ofconventional telephony. The value of an on-demand point-to-point connection isproportional to the number of potential pairs of subscribers, and has beenexpressed as Metcalfes Law. It may be permanent or switched.
Bus Each node is connected to a single cable. Each computer or server is connectedto the single bus cable. A signal from the source travels in both directions to all machines connected onthe bus cable until it finds the intended recipient. If the machine address doesnot match the intended address for the data, the machine ignores the data.Alternatively, if the data matches the machine address, the data is accepted.AdvantagesEasy to setupSmall amount of wireDisadvantagesSlowEasy to crash
Star Each network host is connected to a central hub with a point-to-pointconnection. In Star topology every node (computer workstation or any otherperipheral) is connected to central node called hub or switch. The switch is the server and the peripherals are the clients. The network doesnot necessarily have to resemble a star to be classified as a star network, butall of the nodes on the network must be connected to one central device. Alltraffic that traverses the network passes through the central hub. The hub actsas a signal repeater.AdvantagesEasy to setupOne cable can not crash networkDisadvantagesOne hub crashing downs entirenetworkUses lots of cables
Mesh– All computers connected together– Internet is a mesh networkAdvantage Data will always be deliveredDisadvantages Lots of cable Hard to setup
Tree Tree topology is a combination of Bus and Star topology. The type of network topology in which a central root node (the top level ofthe hierarchy) is connected to one or more other nodes that are one levellower in the hierarchy (i.e., the second level) with a point-to-point linkbetween each of the second level nodes and the top level central root node. Each node in the network having a specific fixed number, of nodes connectedto it at the next lower level in the hierarchy, the number, being referred to asthe branching factor of the hierarchical tree.
Hybrid Hybrid networks use a combination of any two or more topologies in such a waythat the resulting network does not exhibit one of the standard topologies. Ahybrid topology is always produced when two different basic network topologiesare connected. Two common examples for Hybrid network are: star ringnetwork and star bus network.
Daisy chain Except for star-based networks, the easiest way to add more computers into anetwork is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each systembounces it along in sequence until it reaches the destination. A daisy-chainednetwork can take two basic forms: linear and ring.
Linear A linear topology puts a two-way link between one computer and thenext. However, this was expensive in the early days of computing, since eachcomputer (except for the ones at each end) required two receivers andtwo transmitters.
Ring• By connecting the computers at each end of a linear topology, a ringtopology can be formed. An advantage of the ring is that the number oftransmitters and receivers can be cut in half, since a message willeventually loop all of the way around.
Network Hardware• Network interface cards(NIC)– Network adapter– Connects node to the media– Unique Machine Access Code (MAC)
Network linking devices– Connect nodes in the network– Cable runs from node to device– Crossover cable connects two computers
Hubs– Center of a star network– All nodes receive transmittedpackets– Slow and insecure
Switches– Replacement for hubs– Only intended node receives transmission– Fast and secure
Bridge– Connects two or more LANs together– Packets sent to remote LAN cross• Other packets do not cross– Segments the network on MAC addresses
Router– Connects two or more LANs together– Packets sent to remote LAN cross– Network is segmented by IP address– Connect internal networks to the Internet– Need configured before installation
Gateway– Connects two dissimilar networks– Connects coax to twisted pair– Most gateways contained in otherdevices