introduction
A LAN (Local Area Network) is a network of computers that share network traffic. Communication between computers in the same LAN is easy. Communication between computers in different LANs is difficult.
Each DMZ in the LIC contains several LANs.
what it is
A group of computers form a LAN to share resources. LAN resources are things like network printers, file stores and applications.
A domestic LAN contains a couple of computers and an office LAN can contain thousands. A LAN usually only covers an area of a few hundred square meters. MANs and WANs are used to cover bigger areas. A MAN (Metropolitan Area Network) connects computers in several buildings in a city. A WAN (Wide Area Network) connects computers that are geographically far away from each other.
There are several protocols around for letting the computers in a LAN talk to each other.
| common LAN protocols | |
|---|---|
| type | description |
| ethernet | the original and genuine LAN protocol. Ethernet networks typically have computers attached in a bus topology. Computers can transmit data at a maximum speed of 10Mbps (Megabits per second). |
| fast ethernet | a faster replacement for ethernet that has computers attached in a star topology. The computers can communicate at up to 100Mbps. |
| gigabit ethernet | the latest replacement for ethernet. This one goes like a train at up to 1000Mbps. |
| token ring | IBM's idea of arranging computers in a ring topology and letting each computer communicate in turn. A token is used to keep track of whose turn it is. Many token ring networks have been replaced with fast ethernet networks. |
| LocalTalk | Apple's attempt at ethernet. It was damn slow. |
The only type that most small offices and home offices have is fast ethernet. A few use token ring and a few super speedy LANs use FDDI. Most computers use the TCP/IP protocol when they talk to each other but there are the LANs that time forgot that talk protocols such as NetBEUI, IPX, SNA and Appletalk.
All the computers in one LAN share network traffic. If they are all connected to a bus network or are connected by a hub in a star network, they share all the traffic. If they are connected to a switch in a star network, most traffic is filtered out by the switch but they still all hear broadcast and multicast traffic.
A network administrator can make his life easier by taking one big office LAN and split it into several LANs. This makes the network easier to manage than leaving it as one big block. The administrator can do tricky things like move one LAN from the penthouse suite to the basement without affecting the rest, stop the marketing department's network traffic flooding the sales department, and increase security by stopping the IT department hacking the accounts department's wages database.
what it isn't
A LAN is independant of ethernet and TCP/IP. These are protocols usually used in LANs, but in ten years time they may have disappeared from LANs.
A LAN is indepent of network topology. Most LANs are star networks. The idea of a topology is to show the way everything in the network is connected. The idea of a LAN is to show that everything in the network sees the same traffic.
where it is
Like a country made up of counties, the LIC is made up of LANs.
- administration LAN. one interface is for management traffic.
- a web site LAN. two interfaces are used for application traffic (the data that lets punters and websites interact).
