Classification of topologies
Local networks are usually ordered in 2 groups (see classification of networks):
From this first classification we can deduce a hierarchy of the different topologies of local networks:
Interconnexions are of two types:
Finally, the topology we choose for a networks depends on:
The different topologies
Ring or loop networks
This kind of network is not really efficient and reliable but it is quite cheap. As soon as two lines are cut the network no longer works.
We can use this topology for security reasons. It is also used for FDDI (optical fibre) local networks.
Networks in star
Network in star
This topology is quite efficient and cheap. Most small local networks is built on this model (mainly for cost reasons), by using a central hub that connects computers together. Private phone networks (PABX) are also based on this topology. The weakness of this structure is the central node that must never be broken.
Complete networks or with regular meshing
This topology is reliable but it is also the most expensive one. Each node is connected to every other node. It is never used in practice.
It is sometimes used to copy a given hierarchical organization. In practice, it is not efficient because intermediate nodes can be congestion points.
The main characteristic of this topology is that it is a passive structure: is a node is down, the network is not affected. The signal go through the bus and disappears once it has reached an end (terminations on coaxial Ethernet networks).
Undefined network or irregular meshing
Unfortunately it is the most frequent topology. Communication is seldom direct, messages need to go through intermediate nodes. It is not the most efficient and reliable configuration (intermediate nodes can play an important role). This structure is the consequence of interconnection of several local subnetworks.
Copyright © 2000-2002 themanualpage.org - This site is submissive to the terms of the GNU GPL and FDL licences.