Local Area Network (LAN)
The IEEE 802 LAN is a popularly used shared medium peer-to-peer communications network that broadcasts information for all stations to receive.
The LAN enables stations to communicate directly using a common physical medium on a point-to-point basis without any intermediate switching node being required.
A LAN is a system composed of computer hardware and transmission media and
LANs are privately owned networks within a single building or campus of upto few km in range. It generally use only one type of transmission media.
Depends upon application and cost, various topology used in LAN. (e.g. star, bus, ring).
The basic idea of a LAN is to provide easy access to Data Terminal Equipment (DTES) within the office. These DTES are not only computers but other devices, such as printer, plotters and electronic files and databases.
LAN can provide users
Access to the other LAN and WAN
Hardware and software sharing
Private ownership of the LAN.
Aibutes of LAN
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LAN typically identified by the following properties
1 Mules athed to shared muslum. 2. High tal and (-30 Mbps)
3. Low delay.
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Limited pography (1-2 km)
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For laticeship between stations Confined to get property
The low level protocols and in och vinmests are different from those st
The cons of LAN are those described by the IEEE standard 802 The standard describes pettum upto and including Ol layer 2. Individuale may bd what they keeps of the basic protocols A set of higher level protocols is called TCP/IP which provides CSI layer
and & functionality, on top of the may be found a set of priols manly called Telnet protocols
the lowest level the EE 802 specifications split into 3 corresponding to three
dent but comme LAN structions. These are KOA, NA, 825 wandanks for topology LAN are capable of mansmitting data at very fast rates, much faster than data can
bear a telephone line; but the dinonces are limited, and there alt on the number of computers that can be attached to a single
The fillowing characratis differentiate one LAN um another
Topology: The gemetric rangement of device on the network. For ample, deis can be amnged in a ring or in a straight lin
Protocals: The rules and encoding specifications for sending data The proculs also determine whether the network es a peer-to-peer or client were achitecture
Media: Devices can be connected by twisted-pair wire, co-axial cables, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves.
Metropolitan Area Networks (MAN)
A MAN, while larger than LAN is limited to city or group of nearby corporate offices. It uses similar technology of LAN.
The Metropolitan Area Network standards are sponsored by the IEEE, ANSI and the Regional Bell operating companies. The MAN standard is organized around a topology and technique called Distributed Queue Dual Bus (DQDB).
MAN provides the transfer rates from 34 to 150 Mbps.
MAN is designed with two unidirectional buses. Each bus is independent of the other in the transfer of traffic. The topology can be designed as an open bus or a closed configuration.
MANS are based on fiber optic transmission technology and provide high speed interconnection between sites. It can support both data and voice.
MAN as a special category is that a standard has been adopted for them and this standard is now being implemented. It is called IEEEl
Wide Area Networks (WAN)
A WAN provides long distance transmission of data and voice.
A Network that covers a larger area such as a city, state, country or the world is called wide area network.
The WAN contains host and collection of machines. User program is installed on the host and machines. All the host are connected by each other through communication subnet. Subnet carries messages from host to host.
Subnet consists of transmission lines and switching elements. The transmission line is used for data transfer between two machines. Switching elements are used for connecting two transmission lines. Switching elements are specialized computers. It selects the proper outgoing line for incoming data and forward the data on that line.
The switching elements are basically computers and they are called packet switching nodes, intermediate systems and data switching exchanges. These switching elements are also called routers.
Each host is connected to a LAN on which a router is present. Sometimes the how can be directly connected to the router. The interconnection of routers forms the subnet. More
In the WAN, when the packet is sent from one router to another via one or more intermediate routers, the packet is received at each intermediate router in its entirety. This packet is stored in that router until the required output line is free The subnet which uses this principle is called point-to-point, store and forward, or packet switched subnet.
Almost all the WANS use store and forward subnets.
If the packets are small and of same size, they are also called cells.
In the point-to-point subnet, the router interconnection topology becomes
important. WANs can also use satellite or ground radio system. The routers have
antenna, through which they can send or receive data, they can listen from
WAN uses hierarchical addressing because they facilitate routing. Addressing is required to identify which network input is to be connected to which network output.
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