TCP Has Got Widespread Usage in Computer Networking - Essay Example

TCP has got widespread usage in computer networking because of its ability to perceive any congestion in the applied network. It is this ability that has made this protocol intelligent enough to make adjustments in the rate at which it sends data segments. A TCP sender estimates congestion in a network depending on the number of duplicate ACKs. If it receives three duplicate ACKs, it considers the network as congested and loss of that particular segment to which the receiver TCP is sending ACKs. So for the resending of the lost segment, the sender TCP waits for a total of four ACKs from the receiver. But this presumption of congestion by the sender TCP while using the constant threshold technique is not an impeccable procedure and may cause several problems.    2. Give a rough explanation of the proposed solution. The solution proposed by this paper provides a set of modifications at the sender level applying Non-congestion Robustness (NCR) to TCP. The ACK-based system is modified to selective ACK i.e., SACK. This SACK-based segment recovery technique while getting out of the in-order segment transmission strategy, will inform the sender about all segments that have been received and hence the sender will have to retransmit only those segments which have been lost. The TCP-NCR withdraws the TCP from the ACKs-based retransmission technique to the congestion window (cwnd) of data that has left the network. The threshold value, in this case, is very much a dynamic entity with an appropriate choice for the same is a matter of smart decision-making related to the reasons behind duplicate ACKs and responsiveness. The retransmission is triggered after the TCP sender is aware of the fact that the cwnd’s worth of data has left the network.   3. Explain at least one advantage and one disadvantage of the enhancement that is specified in this RFC.  The TCP-NCR technique will result in better TCP performance. With the SACK-based approach, the algorithm despite being a bit complex achieves better performance with less complicated modifications. The modifications result in better packet reordering procedures instead of stressing on ACKs-based segment retransmission technique thereby preventing the TCP from reducing the sending rate due to needless retransmission.    The TCP-NCR has its set of drawbacks. Though it is believed to make changes on the sender side but in reality receivers’ buffering requirement has to be increased up to an extra cwnd. The RTT factor will lead to the introduction of a delay in fast retransmission. The delivery of data to the application could be delayed by at least one RTT. This will virtually make the TCP-NCR useless for those applications which are sensitive to delays of duration nearing RTT.   Read More