A local Area Network (LAN) is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of LANs, in contrast to wide area networks (WANs), include their smaller geographic area, and non-inclusion of leased telecommunication lines.
Ethernet is a 10Mbps LAN that uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol to control access network. When an end station (network device) transmits data, every end station on the LAN receives it. Each end station checks the data packet to see whether the destination address matches its own address. If the addresses match, the end station accepts and processes the packet. If they do not match, it disregards the packet. If two end stations transmit data simultaneously, a collision occurs and the result is a composite, garbled message. Each end station that wants to transmit waits a random amount of time and then attempts to transmit again. This method is usually used for traditional Ethernet LAN.
It has further types:
1).Fast Ethernet – This is an extension of 10Mbps Ethernet standard and supports speed upto 100Mbps. The access method used is CSMA/CD .For physical connections Star wiring topology is used. Fast Ethernet is becoming very popular as an upgradation from 10Mbps Ethernet LAN to Fast Ethernet LAN is quite easy.
2).Gigabit Ethernet -In computer networking, Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second (1,000,000,000 bits per second), as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed considerably faster. There are five physical layer standards for gigabit Ethernet using optical fiber (1000BASE-X), twisted pair cable (1000BASE-T), or balanced copper cable (1000BASE-CX).
3). 10 Gigabit Ethernet-10 Gigabit Ethernet is the latest generation and delivers a data rate of 10 Gbit/s (10,000 Mbit/s), and a fiber optic or twisted pair cable can be used. 10GBASE-LX4, 10GBASE-ER and 10GBASE-SR based on an optical fiber cable can be used to bridge distances of up to 10,000 m (6.2 miles). With a twisted pair solution, a very high quality cable (Cat-6a or Cat-7) is required. 10 Gbit/s Ethernet is mainly used for backbones in high-end applications that require high data rates.
This is a 4-Mbps or 16-Mbps token-passing method, operating in a ring topology. Devices on a Token Ring network get access to the media through token passing. Token and data pass to each station on the ring. The devices pass the token around the ring until one of the computer who wants to transmit data, takes the token and replaces it with a frame. Each device passes the frame to the next device, until the frame reaches its destination.
FDDI (Fiber Distributed Data Interface)
FDDI provides data speed at 100Mbps which is faster than Token Ring and Ethernet LANs. FDDI comprise two independent, counter-rotating rings: a primary ring and a secondary ring. Data flows in opposite directions on the rings. The counter-rotating ring architecture prevents data loss in the event of a link failure, a node failure, or the failure of both the primary and secondary links between any two nodes. This technology is usually implemented for a backbone network.
VLAN(Virtual Local Area Network):
VLAN provides logical connections between different computers. It is very cost effective because in this when computer from one row has to be shifted to other row, then no change in wiring has to be done. The changes can be done only through the softwares.
ATM (Asynchronous Transfer Mode):
This is a cell relay protocol which is made by ATM forum and accepted by ITU-T standards. This provides high speed transmission of data. It has two interfaces i.e. UUI (User to User Interface) and NNI (Network to Network Interface). Switches are connected to each other in NNI. The switches are connected to end points through UUI. Its architecture consists of 3 layers, i.e. physical layer, ATM layer and AAL (Application Adaptation Layer).