The Difference Between Physical And Logical Design Of A Network
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In this paper I will discuss the two different types of design methods used when building a network physical and logical. I will also discuss how each part of these methods works.
When building wireless networks. After all, where is the physical part of the network? In wireless networks, the physical medium we use for communication is obviously electromagnetic energy. But in the context of this chapter, the physical network refers to the mundane topic of where to put things. How do you arrange the equipment so that you can reach your wireless clients? Whether they fill an office building or stretch across many miles, wireless networks are naturally arranged in these three logical configurations; Point-to-point links, Point-to-multipoint links and Multipoint-to-multipoint clouds.
The physical network layout you choose will depend on the nature of the problem you are trying to solve. While different parts of your network can take advantage of all three of these configurations, any individual link will fall into one of the above topologies. The application of each of these topologies is best described by example.
Point-to-point links typically provide an Internet connection where such access isnt otherwise available. One side of a point-to-point link will have an Internet connection, while the other uses the link to reach the Internet. For example, a university may have a fast frame relay or VSAT connection in the middle of campus, but cannot afford such a connection for an important building just off campus. If the main building has an unobstructed view of the remote site, a point-to-point connection can be used to link the two together. This can augment or even replace existing dial-up links. With proper antennas and clear line of sight, reliable point-to-point links in excess of thirty kilometers are possible. Of course, once a single point-to-point connection has been made, more can be used to extend the network even further.
Point-to-point links dont necessarily have to involve Internet access. Suppose you have to physically drive to a remote weather monitoring station, high in the hills, in order to collect the data which it records over time. You could connect the site with a point-to-point link, allowing data collection and monitoring to happen in real-time, without the need to actually travel to the site. Wireless networks can provide enough bandwidth to carry large amounts of data (including audio and video) between any two points that have a connection to each other, even if there is no direct connection to the Internet.
The next most commonly encountered network layout is point-to-multipoint. Whenever several nodes1 are talking to a central point of access, this is a point-to-multipoint application. The typical example of a point-to-multipoint layout is the use of a wireless access point that provides a connection to several laptops. The laptops do not communicate with each other directly, but must be in range of the access point in order to use the network.
The third type of network layout is multipoint-to-multipoint, which is also referred to as an ad-hoc or mesh network. In a multipoint-to-multipoint network, there is no central authority. Every node on the network carries the traffic of every