What are network topologies, what they are for and what are the types of network topologies?
Topologia sieci inaczej mówiąc jest danym sposobem połączenia urządzeń komputerowych za pomocą medium transmisyjnego. LAN topologies are described both physically and logically.
Topologia fizyczna – Its task is to define the geometrical organization of the local computer network, where it graphically shows its shape and structure.
Logical topology – ustala reguły komunikacji, which communication devices on the network use. Devices that can communicate with each other or have direct physical connections to each other can be described as the cause of the logical topology. In local area networks, logical topologies such as:
Broadcasting – zadanie tej topologii polega na tym że host wysyła informację do wszystkich hostów podłączonych do medium. The rule used in the medium determines the order, i.e. "who will send first, the first will be served" (first come, first serve). A good example of this type of topology is Ethernet.
Token upload (chip) – ciekawa topologia polegająca na kontrolowaniu sieciowego dostępu do sieci poprzez przekazanie tokenu (a special data frame). The host that currently has a token, has the ability to use a medium. Conversely, when the host does not need access to the medium, the token is passed to the next host and the cycle repeats itself. FDDI and Token Ring networks use this type of topology.
Basic physical topologies, used in the construction of wired local networks are:
- star (bus)
- ring (ring)
- bus (Star)
All computers and network printers (otherwise it is called network nodes), are always connected with one special coaxial cable. The cable only supports one channel and is therefore called a bus. All nodes are connected with each other by "tees". Both ends of the bus should always be terminated with a so-called terminator, in other words an organic element, which will protect against unwanted signal reflections. No other external devices support the bus, therefore, all devices connected to the network listen to the transmission of the bus and receive the transmitted packets. This type of topology was applicable to small local area networks and worked well a few years ago.
A great advantage of the bus is the short length of the cable used to build the network, no need for hubs and switches and great ease of connecting a new device.
The disadvantage of the bus is that it is very difficult to locate the place where the cable is damaged. When a cable fails, all or part of the network stops functioning.
Each networked workstation has two connections, one to each of its closest neighbors. These types of connections form a physical loop, otherwise known as a ring (ring). All data is transported in one direction around the ring. Each workstation works in the same way as a repeater, it supports and replies to packets addressed to it and transports packets to the next workstation.
A minor disadvantage of this type of connection is that when the cable is damaged, the entire network may become unstable. However, to avoid such situations, double ring or bypass systems are used, which provide additional protection in the event of a failure.
All network connections originate from a central point, which is a hub or switch. W tej topologii dostęp do współdzielonego nośnika może uzyskać każde urządzenie przyłączone do sieci. A very big advantage of the star topology is good throughput and easier location of possible faults. When the link fails, the rest of the computers can continue to work.
The disadvantages may be the high demand for cabling and the need for switches and hubs, the failure of which may lead to the malfunction of the entire computer network. This type of topology has been quite popular recently, because it is flexible, scaled, and relatively inexpensive.