What is topology? What is meant by the local network topology

The term "topology" has a lot of meanings, one of which is used in the computer world to describe networks. What is the topology of computer networks, and will be considered further. But, a little forward, in the simplest case, this concept can be considered as a description of the configuration (location) of computers connected to the network. In other words, it all comes down to understanding not even the connections themselves, but geometric figures that correspond to each type of terminal location.

What is meant by the topology of the local network?

As it is already clear, computers that are integrated into a single network are connected to them not chaotically, but in a strictly defined order. To describe this scheme, an understanding of topology was introduced.

In fact, what is topology? Map, diagram, diagram, map. Descriptive process, as already understood, in something akin to elementary knowledge of geometry. However, only purely from the geometric point of view, this term can not be considered. As it is not only about connections, but also about the transfer of information, this factor should also be taken into account.

The main types of networks and their topologies

In general, there is no single concept of computer topology. It is generally accepted that there may be several types of topologies that collectively describe one or another network organization. Actually, networks can be completely different.

For example, the simplest form of organizing the connection of several computer terminals into a single whole can be called a local network. There are still intermediate types of networks (urban, regional, etc.).

Finally, the largest are global networks that affect large geographic regions and include all other types of networks, as well as computers and telecommunications equipment.

But what is meant by the topology of a local network, as one of the simplest forms of organizing the connection of several computers with each other, in this case?

On the basis of the described processes and structures, they are divided into several types:

• Physical - a description of the existing structure of the location of computers and network nodes, taking into account the relationships between them;
• Logical - the description of the passage of the signal through the network;
• Information - a description of the movement, direction and redirection of data within the network;
• Exchange management - a description of the principle of using or transferring rights to use the network.

Network topology: types

Now a few words about the generally accepted classification of the types of connection topologies. In the context of what a topology is, it's worth mentioning another type of classification that describes only the way the computer connects to the network or the principle of its interaction with other terminals or main nodes. In this case, the concepts of fully connected and incompletely connected topologies become topical.

A fully connected structure (and this is recognized all over the world) is extremely cumbersome because every single terminal that is part of a single network structure is connected to all the others. The inconvenience in this case lies in the fact that for each computer it is necessary to install additional communication equipment, and the terminal itself must be equipped with a sufficiently large number of communication ports. And as a rule, such structures, if they are, are very rare.

Unconnected topology in this plan looks much more preferable, since each individual terminal does not connect to all other computers, but receives or transmits information through certain network nodes or refers directly to the central hub or hub. A striking example of this is the topology of the "star" network.

Since it was the main methods of integrating terminals into a single whole (network), we should dwell on the basic topologies of all the main types, among which the main are "bus", "star" and "ring", although there are some mixed types.

Network topology "bus"

This type of connection of terminals to the network is quite popular, although it has very serious drawbacks.

To consider what the topology "bus" is, it is possible by a simple example. Imagine a cable with several branches on either side. At the end of each such branch is a computer terminal. They are not directly connected with each other, but the information is received and transmitted through a single trunk, at both ends of which special terminators that prevent reflection of the signal are installed. This is the standard line topology of the network.

The advantage of such a connection is that the length of the main trunk decreases significantly, and the output of a single terminal is not affected by the network as a whole. The main drawback is that when the trunk itself is disrupted, the whole network is inoperable. In addition, the topology of the "bus" is limited in the number of connected workstations and has a rather low performance due to the allocation of resources between all terminals in the network. The distribution can be uniform or uneven.

The star topology (star)

The topology of the "star" network in some ways resembles a "bus", with the only difference being that all terminals are connected to a central switchgear (hub) rather than to a single mainline.

Just through the hub, all computers can interact with each other. Information is transferred from the hub to all devices, but it is received only by those to which it is intended. The advantages of such a connection include the possibility of centralized management of all network terminals, as well as the connection of new ones. However, as in the case of the "bus", the failure of the central switching device is fraught with consequences for the entire network.

Topology "ring" (ring)

Finally, we have another type of connection - the ring topology of the network. As, probably, it is already clear from the title, the connection of computers is carried out sequentially from one to another through intermediate nodes, as a result of which a closed circle is formed (naturally, the circle in this case is a conditional concept).

When transferring information from the starting point passes through all the terminals that are facing the final recipient. But the final beneficiary is recognized on the basis of marker access. That is, the information received is only a terminal marked in the information stream. This scheme is practically never used because the failure of one computer automatically entails a disruption in the operation of the entire network.

Mesh and mixed topology

This type of connection can be obtained if you remove some of the links from the above connections or add them in addition. In most cases, this scheme is used in large networks.

In this connection, several basic derivatives can be determined. The most common are schemes like "double ring", "tree", "lattice", "snowflake", "Klose network", etc. As can be seen even from the names, all these are variations on the theme of the main types of connections, which are taken For the basis.

There is also a mixed type of topology, which can combine several other (subnets), grouped by some characteristic features.

Conclusion

Now it is probably clear what topology is. If we make a general summary, this concept is a description of how to connect computers in the network and the interaction between them. How this is done depends solely on the method of integrating the terminals into one whole. And to say that today we can single out one universal connection option, it is impossible. In each case and depending on the needs, one or another type of connection can be used. But in local networks, if we talk about them, the most common is the "star" scheme, although the "bus" is still widely used.

It remains to add that in the network topology, one can still find concepts of centralization and decentralization, but they are mostly connected not with connections, but with the management system of network terminals and the control over them. Centralization is explicitly expressed in star connections, but decentralization is also applicable for this type, providing the input of additional elements in order to increase the reliability of the network when the central switch fails. A rather effective development in this regard is the "hypercube" scheme, but it is very difficult to develop.