Question

Flow-control mechanisms are used at both layers 2 and 3 of X.25. Are both necessary or is this redundant? Explain the problems which can be avoided for having flow control at both layers..

Answer 1

Stream control component utilized at both layer 2 and layer 3 is vital just when there is huge likelihood of more traffic and blunder in any of the connections in the system and this isn't useful for present day advanced correspondence offices. System in this day and age need dependable speedy advanced transmission as opposed to nature of transmission.

X. 25 is a virtual exchanging system and it utilizes broad blunder and stream control at both the information and system layers. The mistake and stream control at both the layers builds the measure of overhead as stream and blunder control at both layer hinders the speed of transmission of information.

The information pace of transmission is 64 kbps which is exceptionally low in X.25. At each bounce in the system information connect control convention includes the trading of information edge and affirmation edges and state tables must be kept up for each virtual circuits to manage mistake and stream control perspectives at both the layers 2 and layer 3.

The X. 25 is a virtual circuit switching network which has three layers as

1)Physical (layer 1)

This level arrangements with physical interface and utilizations the physical standard X. 21.

2)Link (layer 2)

This layer gives solid exchange of information in physical connection by transmitting information in casings and this layer utilizes HDLC significant level information interface conventions

3)packet (layer 3)

This layer gives a coherent association set up called virtual circuits to the clients.

The Problems which can be dodged by utilizing stream control at the two layers

1)The X.25 give affirmation at connect layer on interface by interface premise and at arrange layer so this guarantees dependable transmission of information outlines in system and stream control as different virtual circuits can be carried on a solitary physical connection at each bounce in the system .The connection control convention can be utilized for unwavering quality.

2)Flow control is a strategy for lessening blockage as stream control component restricts the measures of information that sender can send to reciever dependent on his sliding window size.In X. 25 system the stream control at both layer information interface layer and system layer adequately accommodates blockage the executives as both the hubs and connection can be checked for clog. stream control can be utilized on the connection and just as on the virtual circuits that are going through hub to lessen clog.

3)X.25 utilizations a significant level information interface protocol(HDLC) gives succession numbering capacity at information connect layer additionally where as edge hand-off and IP conventions don't give sequencing at information connect layer as it is done on higher layer transport layer.The sequencing of number is significant for stream control instrument.

4)The stream control component at both the layers can deal with the rapid information blasts just as low speed transmissions also.It likewise incorporates hub by hub and bounce to jump blunder and stream control which gives progressively dependable transmission.