Short Answers for Networking

Short Answers and Definitions

September 4, 2006

Network Topologies

Mesh Topology is a network that provides fault tolerance by either using a full mesh topology that provides a direct link between all routers (nodes) from each network segment or is a partial mesh topology which covers only some of the routers on a network segment but not all and this would than provide for less calculation strain on the routers compared to a full mesh.

Bus Topology is a network that hooks up all workstations and hubs on to one single cable in a liner fashion. This was the original form of network used with Ethernet 10Base5. This type of network is very unsecured for reliability, one break in the cable or hub or workstation and you could bring down whole network segments.

Ring Topology is a network in which all the workstations are hooked up in ring formation having the network ends joined to each other to form this circle. This is used in a Token Ring network with a Multistation Access Unit (MAU) at the center and is also used in a Fiber Distributed Data Interface (FDDI) to help form backbones for networks.

Star Topology is a network that has all workstations and servers hook up or link up to an individual hub to form the network. This style helps prevent the network (LAN) from failing completely if one workstation or server goes down. You can build out from the star to create others off of this one to expand the network.

The difference between all of these topologies is simple, Mesh links all the devices on the network to each other and this can be costly and unruly to maintain but provides great fault tolerance. Bus links everything in a liner fashion on one cable and this provides no fault tolerance, if one station goes down the whole network is dead but is very cheap to setup. Ring topology is seldom used these days and just sent a packet around the circle ring until it was picked up. The Star Topology is the most commonly used of these topologies and really only has one bad fault and that is each node (router) could fail and cause a network outage to that branch particular part of the Star network.

Network Architecture

Ethernet network architecture for LAN's can use any networking topology and cabling system. It runs at the physical layer and data-link layer of the OSI model. It can run at speeds from 10Mbps to 1 Gbps and sends its data full duplex, getting rid of the need to use (CSMA/CD) that half-duplex requires to stop collisions. This is the most extensively used architecture in use today for LAN's.

Token Ring is not in great use today and sets up like a physical star topology but runs on a ring topology passing a token around from one workstation to the next but does not let all the stations work independently of each other. Token Ring can only operate at speeds of 4 or 16 Mbps and can only have about 16 workstations per Multistation Access Unit (MAU.)

FIDDI is a high speed network that can run at speeds from 100 Mbps to 200 Mbps