Subburao's Blog

HIGH SPEED NETWORKS

The high speed networks dominates both LAN(local area network) and WAN(Wide Area Networks) markets because of the increased use of multimedia applications and the world wide web.

Basically high speed refers to the rate at which the data in terms of bits, in a network is transfered ie. Bandwidth x latency.

CIRCUIT SWITCHING- it establishes a direct physical connection between the two devices such as phones and computers and creates a temporary connection.

PACKET SWITCHING- Data are transmitted in discrete units called packets.It is of two types namely Datagram approach (takes any path)  and Virtual Circuit Approach(takes a fixed path).

ITU-T  developed the first commercial packet switching named X.25

FUNCTIONALITY OF X.25-

• Physical level(physical connection or wired)
• Link level(Data transfer across physical level as sequence of frames)
• Packet level(logical connection or virtual or imaginary connection)

KEY FEATURES OF X.25-

• Call control packets which are used for setting up and clearing virtual circuits are carried on the same channel
• Multiplexing of virtual circuits at layer 2
• Both layer 2 and 3 include Flow control and error control mechanism

DISADVANTAGES OF X.25-

• Over head occurs in X.25 ie the addition of an extra header in the frame.At each hop through the network the Data level control protocol involves the exchange of the Data Frame and acknowledgement frame.At each immediate node,state tables must be maintained for each virtual circuits to deal with call management
• Due to this disadvantage we make use of the Frame Relay which is faster than this