LAN Topologies
Lord Bones
IT240
Jan 01,
University of Phoenix - AXIA College

LAN Topologies
With this assignment I will discuss some topologies of a LAN as requested by questions 11, 12, and 13, chapter three from the textbook Local Area Networks. A “LAN (Local Area Network) topology is the appearance or layout of a network” (Regan, 2006). There are two forms of topologies of a network, namely, the physical- and logical topology with each its own types of topologies. The physical topology is what someone can see with his or her own eyes, i.e. a workstation, servers, cables, etc. while the logical topology is the dataflow of the network, how the data is moving from one point to another (Regan, 2006). In the following I will describe two physical topology types and one logical topology type, following the scenarios in the question’s mentioned above.
In the first scenario there are four servers in the network with no hub present. The first (A) server is connected to the second (B), third (C), and the fourth (D). The second is connected to the third and fourth, while the third is connected to the fourth. (See figure 1.) This type of physical topology is called a Mesh Topology. A Mesh Topology is a topology where “every computer is linked to every other computer” (Regan, 2006). With this type of topology there is no hub or a similar device present. Also this type is difficult to install and certainly when it has to be reconfigured when a new computer is added to the network and the amount of cables increases dramatically. In the above example there are six cables, but when a server is added the amount of cables increases to nine cables. As you can see it is not a very efficient layout for a LAN network, but there are other topologies that are easier to install and to expand, one of them is the Star Topology which be discussed in the second scenario.

Server A Server B

Server C Server D
Figure 1: Mesh Topology
In the second scenario there are two servers, 15 workstations, and a 24-port bridge. The servers and workstations have each its own dedicated cable between each one and the bridge. This type of topology is called a Star Topology. (See figure 2.) This is a topology in which “every network device connects to a central point such as a hub or switch, which acts as a multipoint connector” (Regan, 2006). This topology is easy to install, expand, or reconfigure. And not only that, it is easier to troubleshoot when a cable breaks or a workstation stops operating. The network is then not affected when a workstation added or replaced, and when a cable breaks, only the workstation that is connected to it is affected. In this scenario there is room for expansion since the bridge has 24 ports and 17 ports are in use, seven workstations, seven servers, or a combination can be added. The topology described here is a physical topology, but this necessarily does not have to be the case. The topology described here is a physical topology, but this necessarily does not have to be the case, it can have a Logical Topology which can be, for instance, a Logical Bus Topology. This brings us to the third scenario.

Figure 2: Star Topology

Even when a Star Topology is installed as a physical topology, this network can function in a different way in how the dataflow is following the pathway along the network. This is called a Logical Topology in where “how the data flows through the physical topology or the actual pathway of the data” (Regan, 2006). Let us use a hub, two workstations, and a server. The cabling will be done by using a cable that has two wires from a workstation or server to a hub. One wire will be used to transmit the data from the workstation or server; the other wire will do the opposite. This will create a Logical Bus Topology. (See figure 3.)

Figure 3: Logical Bus Topology

As you can see there are several topologies or lay outs for a network but it is not limited to what is described above. There are other physical topologies like a bus or ring topology, but also a cellular topology. Also a network can contain a combination, called a Hybrid Topology. This is a topology in where two of the traditional topologies are combined into a larger topology (Regan, 2006). In choosing which topology to install depends on how big or small the network is going to be, if there is an expansion in the future, the size of the company, what kind of work load will be happening, and last but not least what will the budget be to set up a network.

Bibliography
Regan, P. (2006). Local Area Networks. Prentise-Hall.