The offer of local area networks is very wide, with solutions for almost any circumstance. We can select the type of Cable, the Topology and even the type of transmission that best suits our needs. However, of all this offer the most widespread solutions are three: Ethernet, Token Ring and Arcnet.
Comparison of the types of networks
To choose the type of network that best suits our requirements, we have to take into account different factors, such as the number of stations, maximum distance between them, difficulty of wiring, needs for speed of response or to send other information apart from the network data and, of course, the cost.
As a reference for the previous parameters, we can make a comparison of the three types of networks discussed above. To do this, suppose that the Ethernet and Arcnet type are installed with Coaxial Cable and Token Ring with Shielded Twisted Pair Cable. Regarding the ease of installation, Arcnet turns out to be the easiest to install due to its topology. Ethernet and Token Ring require further thought before proceeding with their implementation.
In terms of speed, Ethernet is the fastest, 10/100/1000 Mb / s, Arcnet runs at 2.5 Mb / s and Token Ring at 4 Mb / s. Currently there is a 16 Mb / s version of Token Ring, but it requires a more expensive type of cabling.
As for the price, Arcnet is the one that offers the lowest cost; on the one hand, because the cards installed in PCs for this type of network are cheaper, and on the other, because the cabling is more accessible. Token Ring turns out to be the one with a higher price, because, although the PC boards are cheaper than those of the Ethernet network, nevertheless its wiring turns out to be expensive, among other things because it requires one MAU for each group of eight more users.
Component
- Server: the server is the one or those computers that will share their Hardware and Software resources with the other computers on the network. Its characteristics are computing power, importance of the information it stores and connection with resources that you want to share.
* Workstation: the computers that take the role of workstations take advantage of or have at their disposal the resources offered by the network as well as the services provided by the Servers to which they can access. - Gateway or gateways: it is a Hardware and Software that allows communications between the local network and large computers (Mainframe). The Gateway adapts the communication protocols of the mainframe (X25, SNA, etc.) to those of the network, and vice versa.
- Bridge or bridges: it is a hardware and software that allows two local networks to be connected to each other. An internal bridge is the one that is installed on a Server]] of the network, and an external bridge is the one that is made on a Workstation of the same network. Bridges can also be local or remote. The local bridges are those that connect to networks of the same building, using both internal and external connections. The remote bridges connect different networks to each other, carrying out the connection through public networks, such as the telephone network, ISDN or packet switched network.
- Network card: Also called NIC (or Network Interface Card according to abbreviationfinder). Basically it performs the function of intermediary between the Computer and the communication network. The network communication protocols are recorded on it. Communication with the computer is normally carried out through the expansion slots that it has, either ISA, PCI or PCMCIA. Although some computers have this adapter integrated directly on the motherboard.
- The medium: made up of the cabling and connectors that link the components of the network. The most widely used physical media are twisted pair cable, cable pair, coaxial cable and fiber optics (the latter is increasingly used).
- Cabling hubs: a bus LAN uses only network cards in the stations and coaxial cabling to interconnect them, in addition to the connectors, however this method complicates the maintenance of the network since if any connection fails, the entire network stops working. To prevent these problems, local area networks use cabling hubs to make the connections of the stations, instead of distributing the connections, the hub centralizes them in a single device, maintaining light indicators of their status and preventing one of them from failing. the whole network.
There are two types of cabling hubs:
- Passive concentrators: they act as a simple concentrator whose main function is to interconnect the entire network.
- Active concentrators: in addition to their basic function as a concentrator, they also amplify and regenerate the received signals before they are sent.
Cabling hubs have two types of connections: for stations and to join other hubs and thus increase the size of the Network. Cabling hubs are classified depending on the way they internally make connections and distribute messages. This feature is called a logical topology.
There are two main types:
- Hubs with a logical bus topology (HUB): these devices make the network behave like a bus by sending the signals that reach them through all the connected outputs.
- Concentrators with logical ring topology (MAU): they behave as if the network were a ring, sending the signal that reaches them through one port to the next.
Description of the figure
The network is connected to the Internet. This is protected from external attacks by means of a Firewall (not completely protected). Then it goes to a demilitarized zone. In this area are the servers that have contact with the outside and also protect the internal network. The servers are communicated with the workstations, through a Hub or Switch. The clients of this network are stations that run operating systems such as MacOS X, GNU / Linux and Windows. We also have a network printer and we can have other peripherals such as scanners, faxes, etc. (some of these requiring additional software to get the job done). You can see in this network a wireless device, Bluetooth and any other that shows the necessary characteristics for the operation of a local network.
