The network topology characterizes the properties of networks that do not depend on their size, reflects the structure formed by the network nodes and the many channels connecting them. It does not take into account the performance and principle of operation of these nodes, their types and the length of the channels.
From the point of view of the physical location of the functional network components (cables, workstations, etc.) and the method of access to the transmission medium to the network resources, four basic topologies can be distinguished: "common bus", "star", "ring" and "cellular".
When building a network of intercoms, topology star or mixed topology is most often used.
A network with a star topology is a tree network in which there is exactly one intermediate node. The central part is a router or switch of level 3.
The network has one central node and the stations radiating from it with peripheral devices at the ends (Fig. 1.2). In such a network, all stations are directly connected to the central router, which controls the flow of messages on the network, and messages from one station to another can be transmitted only through the central node.
Fig. 1.2. Network layout with a star topology
You can expand the star topology by connecting another switch instead of one router and connecting additional machines to it. This creates a hybrid star-shaped network (Fig. 1.3).
Fig. 1.3. Hybrid Star Network Diagram
The advantages of a star topology network are that:
- such a network allows simple modification and addition of computers without disturbing the rest of it;
- the central router of a star topology is convenient to use for diagnostics;
- failure of a single computer does not always stop the entire network;
- several types of cables are allowed on the same network.
The disadvantages of a network with a star topology are that:
- if the central router fails, the entire network becomes inoperable;
- typically, large cable lengths are used (depending on the location of the central router) and, therefore, such networks are more expensive than networks with a different topology.