Host A has a file of 49.5Kbytes to send to host C and host B has...

 

 

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Host A has a file of 49.5Kbytes to send to host C and host B has a file of 70.5Kbytes to send to host D, both using TCP. TCP connection 1 from A to C and TCP connection 2 from B to D share one bottleneck link of 750Kbps in the network, as shown in Figure 5. The file transmissions from host A and from host C start at the same time. The round-trip time (RTT) between A and C and between B and D is both 0.2 seconds (ignore detailed propagation, queueing, and nodal processing delays and just consider the RTT). Suppose time is slotted according to RTT and we start from RTT 1. In both TCP connections: the congestion control process starts with slow start until the slow start threshold (ssthresh) has been reached, and then begins AIMD and reacts to loss events detected by timer timeouts by cutting ssthresh to half and following slow start again. In this question, we do not consider duplicated ACK nor fast recovery, and assume exactly 1MSS is added to a sender's congestion window (CongWin) in each RTT during AIMD (instead of CongWin = CongWin + MSS * MSS/ CongWin per new ACK). A receiver sends an ACK immediately after it has received a segment; ignore ACK transmission time. In this way, batches of segments are sent out from each sender in the Mt RTT (M=1,2,...) and ACKS for each batch of segments are received back at the sender in the (M+1)th RTT (M=1,2,...). Suppose each sender's timer expires after 1RTT, the initial ssthresh is 16MSS, and the size of each TCP segment is 1MSS-500bytes. 1 2 3 4 A TCP connection 2 Figure 5 (1) (10 %) Complete the following table for congestion window sizes and slow start thresholds: fill in CongWin size and ssthresh for TCP connection 1 until the RTT when host A's file transfer is completed; fill in CongWin size and ssthresh for TCP connection 2 until the RTT when host B's file transfer is completed. [Hints: consider a loss will occur in each TCP connection in an RTT if the overall data rate in that RTT exceeds the bottleneck link's capacity; compute how many RTTS host A's file transfer takes and how many RTTS host B's file transfer lasts.] Time (in RTTS) CongWin of TCP connection 1 (in MSS) ssthresh of TCP connection 1 (in MSS) 1 5 6 B TCP connection 1 750Kbps C 16 CongWin of TCP connection 2 (in MSS) 1 ssthresh of TCP connection 2 (in MSS) 16 Host A has a file of 49.5Kbytes to send to host C and host B has a file of 70.5Kbytes to send to host D, both using TCP. TCP connection 1 from A to C and TCP connection 2 from B to D share one bottleneck link of 750Kbps in the network, as shown in Figure 5. The file transmissions from host A and from host C start at the same time. The round-trip time (RTT) between A and C and between B and D is both 0.2 seconds (ignore detailed propagation, queueing, and nodal processing delays and just consider the RTT). Suppose time is slotted according to RTT and we start from RTT 1. In both TCP connections: the congestion control process starts with slow start until the slow start threshold (ssthresh) has been reached, and then begins AIMD and reacts to loss events detected by timer timeouts by cutting ssthresh to half and following slow start again. In this question, we do not consider duplicated ACK nor fast recovery, and assume exactly 1MSS is added to a sender's congestion window (CongWin) in each RTT during AIMD (instead of CongWin = CongWin + MSS * MSS/ CongWin per new ACK). A receiver sends an ACK immediately after it has received a segment; ignore ACK transmission time. In this way, batches of segments are sent out from each sender in the Mt RTT (M=1,2,...) and ACKS for each batch of segments are received back at the sender in the (M+1)th RTT (M=1,2,...). Suppose each sender's timer expires after 1RTT, the initial ssthresh is 16MSS, and the size of each TCP segment is 1MSS-500bytes. 1 2 3 4 A TCP connection 2 Figure 5 (1) (10 %) Complete the following table for congestion window sizes and slow start thresholds: fill in CongWin size and ssthresh for TCP connection 1 until the RTT when host A's file transfer is completed; fill in CongWin size and ssthresh for TCP connection 2 until the RTT when host B's file transfer is completed. [Hints: consider a loss will occur in each TCP connection in an RTT if the overall data rate in that RTT exceeds the bottleneck link's capacity; compute how many RTTS host A's file transfer takes and how many RTTS host B's file transfer lasts.] Time (in RTTS) CongWin of TCP connection 1 (in MSS) ssthresh of TCP connection 1 (in MSS) 1 5 6 B TCP connection 1 750Kbps C 16 CongWin of TCP connection 2 (in MSS) 1 ssthresh of TCP connection 2 (in MSS) 16

Answer rating: 100% (QA)

To complete the table for congestion window sizes and slow start thresholds lets calculate the number of RTTs required for each file transfer to compl... View the full answer