LAN Technologies (Ethernet,Token ring)

A local area network(LAN) is a set of connected devices through a common communication line or wireless link and share resources of a single processor or server within a small geographical area.Typically a common server is present and all the rest of devices use the resource of the server.The most common technologies are

• Ethernet 
• Token Ring
• FDDI

Ethernet:

Ethernet protocol is widely used among the LAN technologies.It uses CSMA/CD(Carrier Sense Multiple Access/Collision Detection).In these process each computer in the LAN system listen through the totla LAN to find is it idle/clear or not.If it senses the network is clear it sends the data.If it senses the line is busy it waits for the line to be clear.Sometimes two computers try to send data at same time, and the collision occurs.In that instant both computers wait for random amount of time and retransmit the data again.The Ethernet protocol is used in linear,bus,star and tree topologies.

Ethernet 100Base T

Token Ring:

The token ring technology is widely used LAN technology.It is network of connected computer which creates a logical ring.The network has a token signal which travels from one computer to another.If some computer in the network wants to transmit data it just grab the token and sends the data.While transmitting data the token is made unavailable to the network.After transmission of data the computer release the token and made it available to the network again.That's how it avoids the collision in the network.It can operate at transmission speeds of 4 to 16Mbps.

Token Ring Technology

FDDI:

Fiber Distributed Data Interface(FDDI) is a protocol used to connect two or more networks,often over a large distance. FDDI uses token passing and dual ring physical topology.

Other than these technologies there is LocalTalk used by Macintosh computers and uses the technology of CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance).