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… on Modified Network Layer to Support Real-time Service

Real-time transfer suggests that when a request has been made, it is immediately communicated to the recipient. Hence, putting off packet transmissions, no matter how much of a fraction of a second, would be undesirable.

Currently, TCP handles packet transmissions with the aid of acknowledgements and waiting for acknowledgements could possibly result to transmission delays. To support real-time transfer in TCP, we suggest to remove the retransmission of lost packets to lessen latency and delay of receiving packets. For audio/video applications, minor loss of data is tolerable.

To minimize packet losses, the window size would still adapt the slow start, additive increase and multiplicative decrease of window size protocol. This will still provide the balance between the load and the fairness of the network.

For applications that do not tolerate data loss and requires reliability, the packets will be sent in duplicates. The amount of duplicates are determined on how often the timeouts occur. Upon a timeout, the transmission window would increase the allocation of the duplicates. The amount of duplicate packets would increase say from 10% to 15% of the current window size. This will continue to increase up to 50% maximum (all packets will be sent with duplicates).
On the next sending and if there is no time-out received on the previous data sent, the number of redundant packets to be sent would be decreased by say 5% or 10%. This would continue until there is no more duplicate packets sent.

It should be noted that duplicate packets will not congest the network since the window size is decreased during timeouts. However, the number of redundant packets are to be increased. The trade-off with this method is the efficiency of the usage of the resources against the reliability of the transfer.

Another thing to consider is to determine packets to duplicate. Certain packets may hold important data which if lost would translate to an incomplete and incomprehensible message. It would also be inefficient to send multiple packets that would be discarded at the receiving end.

posted by ninoy in CS 255 and have No Comments

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