Local Area Network is short for LAN according to abbreviationfinder. A local area network, local network or LAN (local area network) is the interconnection of several Computers and Peripherals. Its extension is physically limited to a building or an environment of 200 meters, or with Repeaters it could reach the distance of a field of 1 kilometer. Its most widespread application is the interconnection of personal computers and workstations in offices, factories, etc., to share resources and exchange Data and Applications. In short, it allows a connection between two or more computers.
The term local network includes both the Hardware and the Software necessary for the interconnection of the different devices and the processing of information.
Evolution
The first networks were time-shared, the same ones that used Mainframes and connected terminals.
Such environments were implemented with the SNA (Systems Architecture Network) of IBM (International machines bussines) and Architecture Digital Network.
LANs (Local Area Networks) emerged from the PC revolution. LANs allowed Users located in a relatively small geographic area to exchange messages and files, and have access to shared Resources throughout the Network, such as File or Application Servers.
With the advent of Netware came a new solution, which offered: impartial support for the more than forty existing types of cards, cables and operating systems much more sophisticated than those offered by most of the competitors. Netware dominated the LAN field of personal computers from before its introduction in 1983 until the mid- 1990s, when Microsoft introduced Windows NT Advance Server and Windows for Workgroups.
Of all Netware’s competitors, only Banyan VINES had comparable technical power, but Banyan gained a secure base. Microsoft and 3Comworked together to create a simple network operating system which was made up of the foundation of 3Com’s 3 + Share, Microsoft’s Lan Network Manager, and IBM’s Server. None of these projects were very satisfactory.
Advantage
In a company there are usually many computers, which need their own printer to print reports (Hardware redundancy), the data stored in one of the computers is very likely to be necessary in another of the company’s computers, so It will be necessary to copy them in this, being able to produce lags between the data of two users, the occupation of the Storage resources on disk is multiplied (data redundancy), the computers that work with the same data will have to have the same programs to handle said data (Software redundancy), etc.
The solution to these problems is called a local area network, it allows sharing Databases (data redundancy is eliminated), Programs (Softwareredundancy is eliminated) and Peripherals such as a Modem, an ISDN Card, a Printer, etc. (Hardware redundancy is eliminated); making other means of communication available to us such as Email and Chat. It allows us to carry out a distributed process, that is, the tasks can be distributed in different nodes and allows us the integration of the processes and data of each of the Users in a corporate work system. Having the possibility of centralizing information or procedures facilitates the administration and management of the teams.
In addition, a local area network entails significant savings, both in time, since information and work management is achieved, as well as money, since it is not necessary to buy many Peripherals, less paper is consumed, and in a connection to Internet can be used a single telephone or Broadband connection shared by several computers connected in the Network.
Important features
- Broadcast technology (broadcast) with the shared transmission medium.
- Transmission capacity between 1 Mbps and 1 Gbps.
- Maximum extension no more than 3 km (an FDDI can reach 200 km)
- Use of a private means of communication
- The simplicity of the transmission medium it uses (Coaxial Cable, Telephone Cables and Optical Fiber)
- The ease with which changes can be made to Hardware and Software
- Great variety and number of connected devices
- Possibility of connection with other networks
- Limiting 100 m, can reach more if repeaters are used.
Network topology
Network topology defines the structure of a network. A part of the topological definition is the Physical Topology, which is the actual arrangement of the Cables or media. The other part is the Logical Topology, which defines how Hosts access the media to send data. The most commonly used topologies are the following:
Physical topologies
- A circular bus topology uses a single backbone cable that must be terminated at both ends. All Hosts connect directly to this Backbone.
- The Ring topology connects one host to the next and the last host to the first. This creates a physical ring of wire.
- The star topology connects all cables to a central point of concentration.
- An Extended Star Topology connects individual stars to each other by connecting Hubs or Switches. This topology can extend the reach and coverage of the network.
- A hierarchical topology is similar to an extended star. But instead of connecting the HUBs or Switches to each other, the system connects to a computer that controls the traffic of the topology.
- The Mesh Topology is implemented to provide the highest possible protection to avoid a service interruption. The use of a mesh topology in the networked control systems of a nuclear plant would be an excellent example. In this topology, each Host has its own connections to the other hosts. Although the Internet has multiple paths to any location, it does not adopt the full mesh topology.
- The Tree Topology has several terminals connected so that the network branches from a Base Server.
Logical topologies
The logical topology of a network is the way that hosts communicate across the medium. The two most common types of logical topologies are broadcast and token broadcast.
- The topology broadcast simply means that each host sends its data to all other hosts on the network medium. There is no order that stations must follow to use the network. It’s first come, first served, it’s how Ethernet works.
- The Token Transmission Topology controls access to the network by transmitting an electronic Token to each Host sequentially. When a host receives the token, that Host can send data over the network. If the host doesn’t have any data to send, it passes the token to the next host and the process repeats itself. Two examples of networks that use token transmission are Token Ring and Fiber Distributed Data Interface (FDDI). Arcnet is a variation of Token Ring and FDDI. Arcnet is the transmission of Tokens in a Bus Topology.
