What are the requirements of wide area network?

Answer 1

• When a network spans a large geographical area, some form of standards must be applied to endure a uniform service throughout the WAN.

• The standard which are important:

1. X.25

2. Frame Relay

3. ATM

X.25

• The use of this protocol started in the 1970's.

• X.25 protocol started its way due to the need to provide users with wide area network (WAN) connectivity across public data networks (PDNs).

• X.25 protocol was the most popular one among others that were developed at that time.

• X.25 was developed by the common carriers, rather than any single commercial enterprise.

• Because of that, the specifications of the protocol are well suited to various system types.

• X.25 has been created in order to exchange data over WAN (Wide Area Network).

• The X.25 is a protocol for packet switching.

• The first version of the protocol was intended to work on a network with lower speed, end-to-end error detection and correction over noisy analog lines.

• The X.25 protocol has been developed due to the need to connect between lots of computer sites.

• The main role was to assure interoperability among various vendor products.

• Another goal was to maximize the sharing of network resources.

• X.25 protocol has methodologies for the three lowest layers:

• physical

• data-link and

• network

• It defines an "open" system connection by creating a standard interface for each layer.

• Therefore, it enables compatibility of multi-vendor hardware and software systems.

Frame Relay

• X.25 networks provides a consistent data rate for the user whether or not that bandwidth is used up.

• This is inefficient in terms of the bursty nature of data on a network.

• Frame Relay was created to cater to a higher data rate demand from users without incurring more costs.

• Frame relay consists of an efficient data transmission technique used to send digital information.

• It is a message forwarding "relay race" like system in which data packets, called frames, are passed from one or many start-points to one or many destinations via a series of intermediate node points.

ATM

• ATM Networks are connection-oriented.

• Communication first initializes by sending a first packet to setup the connection.

• The setup packet makes its way through the subnet, by making entries in the tables of intermediate routers.

• These connections takes the form of virtual circuits.

• The header part of the cell contains the connection identifier.

• The connection identifier tells all intermediate routers which cells belong to which connections.

• In ATM, cell routing is done in hardware, at high speed.

• Having fixed size cells is an advantage because its easy to build hardware routers to handle short, fized-size cells.

• Variable-length IP packets have to be routed by software, which is a slower process.