Network Basics

When dealing with networks one has to understand the different types and how they are used along with the advantages and disadvantages of each.

A mesh network allows for redundancy in that if one node goes down all terminals are able to still communicate with other terminals and networks by taking several possible paths. The mesh network will be more complex and time consuming to install, but is also the more reliable than other topologies. If each terminal having reliable connectivity is mission critical, the knowledge is available and cost is not really a factor then a mesh would be the preferred network.

Bus topology is probably the least preferred topology to implement. If one node is removed or non-operational on the bus then all terminals will not be able to utilize the network. According to Annabel Dodd (2005) "Prior to hubs, each device in a LAN was wired to another device in a "bus" arrangement."(p. 26) Circumstances that may play a factor in this use of this particular topology would be cost savings in regards to cable and the importance of that particular network to the department's mission, as well as the network's size as well as security. Required speed, number of attachments, cable length, and use play a factor in determining the use of the bus topology. Bates & Gregory (2000) tell us that bus speed is limited to "10Mbits/s with effective throughput of 3.3-4 Mbits/s" and that attachments cannot exceed "1024 addressable nodes" and are "limited to cable lengths of 1500 meters." They continue on to say that "collisions when the network gets 40% busy, resulting in less throughput." It seems that the bus topology is also the least secure in respect to the fact that all transmissions are a broadcast to the entire network.

The star topology is another network architecture. Circumstances to install this type of network would be similar to those of the bus topology. The star topology would be primarily used with hubs and switches. This topology allows for all terminals to continually communicate on the network when a terminal is dropped or goes down. This type of topology is important when connectivity of each terminal in the network is important and is mission critical to operations.

Combinations of all the various topologies will be seen in MAN, WAN, and even some larger LANs. An example would be a college campus in which each department uses a star topology internally, but meshes with all the other outlying departments. So in the case of a college campus all departments would still be able to access records from other departments on campus when one or more departments lose connectivity.

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