Topologies

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The word topology is commonly used to discuss the properties of various types of networks. It comes from the branch of mathematics that examines the characteristics of geometric shapes. Networks have shapes, and those shapes have much to do with how it functions.
There are two different types of topology, physical and logical. The physical topology of a network is the actual layout or appearance of the cables and computer on the network. All physical topologies are variations of two fundamental methods of connecting devices, a point-to-point or multipoint. A point-to-point (PTP) topology connects two nodes together. The following examples are pure PTP:



• Two computers communicating via modems
• A mainframe terminal communicating with a front-end processor
• A workstation communicating along a parallel cable to a printer

In a PTP link, two devices control the Communication medium. Because the medium is not shared with other devices, a mechanism is not needed to identify the computers. A simple PTP Two device has no need for addressing. A PTP can be simplex which the communication goes one way only. A half-duplex were the transmission goes two ways, but only one direction at a time, or a full-duplex were the transmission goes both ways simultaneously.
If you wanted to link three or more devices together through a single communication medium you would probably use a multipoint topology. Multipoint works much like a party-line telephone service where several users are connected to the same line. Because they share a common channel, each device needs a way to identify itself and the device it wants to send information. The method that they use is by assigning addresses.
The following four types of physical topologies are frequently used in computer networking:
1. Star
2. Bus
3. Ring
4. Hybrid
The star topology is a popular method of connecting the cabling in a computer network. In a star, each device connects...