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 further considered. But, looking a little ahead, 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 shapes that correspond to each type of terminal arrangement.
What is meant by the topology of the local network?
As it is already clear, computers united in unified networks are connected to them not randomly, but in a strictly defined order. To describe this scheme, an understanding of topology was introduced.
In essence, what is a topology? Map, diagram, chart, map. The descriptive process, as is already clear, is somewhat akin to elementary knowledge of geometry. However, only from a geometric point of view, this term cannot be considered. Since this is not only about connections, but also about the transfer of information, in this regard, this factor should 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 can be several types of topologies that together describe one or another network organization. Actually, the 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 the global networks, which affect large geographic regions and include all other types of networks, as well as computers and telecommunications equipment.
But what is understood by the topology of the local network as one of the simplest forms of organizing the connection of several computers to each other, in this case?
Based on the described processes and structures, they are divided into several types:
- physical - a description of the actual existing structure of the location of computers and network nodes, taking into account the relationships between them;
- logical - a description of the signal flow through the network;
- informational - a description of the movement, direction and redirection of data within the network;
- exchange management - a description of the principle of use or transfer of rights to use the network.
Network Topology: Types
Now a few words about the generally accepted classification of topology types by relationship. In the context of what a topology is, it is worth mentioning one more type of classification that describes only the way a computer connects to a 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 relevant.
A fully-connected structure (and this is recognized around the world) is extremely cumbersome due to the fact that each single terminal that is part of a single network structure is connected to all the others. The inconvenience in this case is 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 applied, are extremely rare.
An incomplete topology in this regard looks much preferable, since each individual terminal does not connect to all other computers, but receives or transmits information through certain network nodes or addresses directly to a central hub or hub. A striking example of this is the star network topology.
Since we are talking about the basic methods of combining terminals into a single whole (network), we should dwell on the basic topologies of all the main types, among which the main ones are the "bus", "star" and "ring", although there are some mixed types.
Bus network topology
This type of networking of terminals is quite popular, although it has very serious drawbacks.
Consider what a bus topology is, using a simple example. Imagine a cable with several branches on both sides. At the end of each such branch is a computer terminal. They are not directly connected to each other, but they receive and transmit information through a single highway, at both ends of which special terminators are installed that prevent signal reflection. This is the standard linear network topology.
The advantage of such a connection is that the length of the main trunk is significantly reduced, and the failure of a single terminal on the network as a whole has no effect. The main disadvantage is that in case of violations in the work of the main itself, the entire network turns out to be inoperative. In addition, the bus topology is limited in the number of connected workstations and has a rather low productivity due to the distribution of resources between all terminals on the network. Distribution may be uniform or uneven.
Star Topology
The star network topology in a sense resembles a bus, with the only difference being that all terminals are connected not to a single trunk, but to a central switchgear (hub, hub).
Just through the hub, all computers can interact with each other. Information is transmitted from the hub to all devices, but is accepted only by those for which it is intended. The advantages of this 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.
Ring Topology
Finally, we have yet another type of connection - a ring network topology. As probably the name implies, computers are connected sequentially from one to another through intermediate nodes, as a result of which a vicious circle forms (naturally, the circle in this case is a conditional concept).
When transmitting information from the starting point passes through all the terminals that are facing the final recipient. But the recognition of the final beneficiary is based on token access. That is, information is received only by the terminal marked in the information stream. Such a scheme is practically never used due to the fact that 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 connections from the above connections or add them additionally. In most cases, such a scheme is used in large networks.
In this regard, several basic derivatives can be defined. The most common schemes are the types of “double ring”, “tree”, “lattice”, “snowflake”, “Klose network”, etc. As you can see even from the names, all these are variations on the main types of compounds, which are taken as a basis.
There is also a mixed type of topology, which can combine several others (subnets), grouped by some characteristic features.
Conclusion
Now it’s probably clear what a topology is. If you make a general result, this concept is a description of how computers are connected to the network and the interaction between them. How this is done depends solely on the method of combining the terminals into a single whole. And to say that today it is possible to single out any one universal connection option 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 specifically about them, the most common is the "star" scheme, although the "bus" is still used quite widely.
It remains to add that in the network topology one can also find the concepts of centralization and decentralization, but for the most part they are not connected with connections, but with the control system for network terminals and the control over them. Centralization is clearly expressed in star-type 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 fairly effective development in this regard is the hypercube scheme, but it is very difficult to develop.