Topology "ring": disadvantages and advantages

The network topology is a physical and logical way to integrate a group of computers into a single network. The most common network topology is "bus", "star", "ring". Each of them has its advantages and disadvantages and is used depending on the situation. All of them are somehow used in the construction of modern local networks. Let's look at their key features, learn the strengths and weaknesses of each.

"Tire"

This kind of organization of the local network provides for the use of a single cable, through which all the workstations that are used are combined. Each of them transmits a signal to all computers connected to the line, but only the one whose address is indicated in the packet receives the data. The rest simply ignore the information received.

In the "common bus" topology, terminators that are located at the ends of the main cable are necessarily used and suppress signals reaching them, in order to avoid their reflection. Without these devices, collisions would inevitably arise in such a network, because of which normal work would not be possible. Of course, collisions still arise, but thanks to the terminators, their number is minimal. If this does happen, the station simply sends the packet anew through a random time interval determined by the algorithm.

Advantages of topology "tire"

This organization of the network has several advantages over other methods. Among them - low cost of construction and ease of its creation. It is quite easy to organize such a local network, you only need to extend the "common bus" and connect computers to it through special connectors. This topology assumes a small consumption of the network cable, since only small segments are used that connect the "bus" to the workstation.

It makes sense to use a "common bus" in small offices or, conversely, on highways that connect several networks together. One of the advantages of this topology is that if one of the workstations fails, the network is not broken. The rest of its members can continue their work as if nothing had happened. When you connect a new computer, there is no need to stop the network, which is also an indisputable plus of the "common bus".

Disadvantages of the "common bus"

Disadvantages of this topology are due to the same reasons as its dignity. For example, connecting all computers with a single cable significantly reduces the reliability of the network. A break in the "bus" anywhere will put an end to the entire system. In networks with such a topology, it is very difficult to diagnose a malfunction. Another disadvantage of the "bus" is its low performance. All data of such a network passes through one cable. This makes it impossible to work at high speeds.

Another stone in the garden "common bus" - the dependence of the speed of work on the number of computers in the network. Since workstations have to communicate through one communication channel, the more computers will be connected to such a network, the lower the speed of its work. That is, the "common bus" is well suited for a small number of nodes that do not require a serious level of security. After all, with security, this kind of topology also has problems. The matter is that each client in such a network has access to information of other computers.

Topology "ring"

This kind of organization of the local network is arranged so that each computer in it is connected to the next one until the chain closes, forming a ring. The signal in such a network passes in one direction, from one computer to another, until it reaches the addressee. To determine the workstation that is transmitting information at the moment, a marker is used. Computers transmit it in turn until it reaches the node that wants to send the data. Then he sends the information in batches, one by one, without waiting for a confirmation of the delivery. The workstation receiving the data, in turn, sends a report on the receipt of the packet. After receiving a confirmation of delivery, the computer sends the marker further in a circle so that someone else can use it. In this unpretentious way, the network topology "ring" is organized. This design has both advantages and disadvantages.

The benefits of "rings"

The advantage of this topology is its simplicity. Such a network is very easy to implement, and it does not require serious cable costs. A power cord is needed only for laying from one computer to another, there are no additional costs. Also in the "ring" you can achieve a high data transfer speed, because to send a package you do not need to wait for a delivery report.

Another plus of networks with a similar organization - they can have a large length. In this case, there is no need to amplify the signal with the help of additional equipment, since each workstation updates and restores the data itself. But behind the simplicity and cheapness of this topology are the shortcomings that made its application very limited.

Topology "ring": disadvantages

When creating a network of this type, you need to remember that its reliability leaves much to be desired. The reason for this is that its performance depends on each computer that is included in it. That is, if one of the workstations is broken, then the entire network stops functioning. The topology "ring" also assumes that to connect a new computer you need to completely stop the network, and this is very inconvenient for both the administrator and users.

Another reason not to use this topology is low performance with a large number of workstations. Since the data is constantly circling, every new client on the network slows down its work. Moreover, one old computer can make a ring-type network incredibly slow, regardless of the speed of the other members of the ring. All this significantly limits the application of this topology in modern networks, but in some cases its use is justified.

"Star"

Probably the most common topology of the network is the "star". "Ring", discussed above, is used much less often, and the "common bus" too. In a network with a star topology, workstations are directly connected to the hub. This important element of the network can be either active, signal restoring, or passive, which simply provides the physical connection of the cable. The server is also connected to the hub, like other computers, which makes communication between them extremely simple.

Usually the network size with the star topology is limited only by the number of ports on the hub, but theoretically there can not be more than 1024, although it is difficult to imagine a hub with such a number of ports. Through the hub, all traffic passes through a network of the "star" type, so that the reliability and efficiency of the entire system depends entirely on this device.

Pros of the topology "star"

If you need to build a fast and reliable network, then an excellent choice is the topology "star". "Ring" or "common bus" can also be used on some sections of the network. The pros of the "star" - in its reliability and simplicity. Each workstation has a separate network cable, which is very convenient and practical. Thanks to this in such a network it is very simple to find and fix problems, and its maintenance takes much less time and nerves. When connecting new computers to a network of the "star" type, it remains operational, unlike other build options. For example, the topology "ring" can not boast of such flexibility.

The speed in the network with the topology of the "star" is limited only by the bandwidth of the cable and the ports of the hub. Also in such a network there are no collisions of transmitted information. Each computer transmits its data via a separate cable. If you need a large network, you can combine several networks with the topology of the "star". Despite all its advantages, this type of networking has its drawbacks.

Disadvantages of the "star"

If a hub breaks in a network with a star topology, it will stop working. Such dependence on one element of the system significantly reduces the reliability of the network. Another problem is the high cost of installation. For each workstation, a dedicated cable is selected, which you want to hold and secure. So to the price of the cable you can add the cost of communications and boxes for it, and it turns out that the "star" will cost much more than, for example, the topology of the "ring".

Another drawback of the "star" topology is the maximum length of the cable to the workstation. It should not exceed 100 m, otherwise the signal will be weakened and distorted. Therefore, the coverage radius of such a network does not exceed 200x200 meters. For further expansion it will be necessary to add additional concentrators to the network.

Combining topologies

So, you got acquainted with all the options, but did not decide what kind of topology you need - "bus", "star", "ring"? This is not surprising, since modern networks often require a combination of topologies. For example, several servers can be combined into a "common bus", but each of them will have a branch with a star topology. Depending on the task to be performed, the LAN device can be very diverse. You can find such options in which each computer is connected to each, although this is a big rarity. Another interesting option - two "rings" that have one common computer.

At enterprises, you can often find different topologies within a single building. The whole network can be built in the form of a "star", but in separate offices the topology "ring" or "common bus" is organized. In large networks, combining different types of network organization is often the only way to solve the task. After all, in the end, it does not matter what you have - "star", "ring", "tire." The topology of the network is needed only to solve practical problems. Your network works stably and solves all the tasks assigned to it? Then it does not matter which topology was used to create it.