This material may not be reproduced in printed or electronic format without the express permission of the author.
NETWORK SEGMENTS
A network segment
Large networks are made by combining several individual network segments together, using appropriate devices like routers and/or bridges.
In the above diagram, a bridge is used to allow traffic from one network segment to the other. Each network segment is considered unique and has its own limits of distance and the number of connections possible.
When network segments are combined into a single large network, paths exist between the individual network segments. These paths are called routes, and devices like routers and bridges keep tables which define how to get to a particular computer on the network. When a packet arrives, the router/bridge will look at the destination address of the packet, and determine which network segment the packet is to be transmitted on in order to get to its destination.
In the above diagram, a packet arrives whose destination is segment B. The bridge forwards this incoming packet from segment A to the B segment.
Sometimes, a loop would be created which caused the wrong packets to be sent on incorrect segments. These packets could loop around the network, being forwarded on, eventually arriving back, only to be forwarded on, etc. This quickly floods the network. The spanning tree algorithm is a software algorithm which defines how switches and bridges can communicate and avoid network loops.
Packets are exchanged between bridges/switches, and they establish a single path for reaching any particular network segment. This is a continuous process, so that if a bridge/switch fails, the remaining devices can reconfigure the routing tables to allow each segment to be reached.
To be effective, ensure that the bridges/switches in use in your network support this protocol.