18. Suppose two TCP connections have the same RTT and share a bottleneck link, f

Question

18. Suppose two TCP connections have the same RTT and share a bottleneck link, for which there is no other competition. The size of the bottleneck queue is negligible when compared to the bandwidth × RTTnoLoad product. Loss events occur at regular intervals.

3. Suppose a TCP Vegas connection has R as its bottleneck router. The transit capacity is M, and the queue utilization is currently Q>0 (meaning that the transit path is 100% utilized, although not necessarily by the TCP Vegas packets). The current TCP Vegas cwnd is cwndV. Show that the number of packets TCP Vegas calculates are in the queue, queue_use, is

queue_use = cwndV×Q/(Q+M)

Explanation / Answer

18) TCP connection means traffic which means congestion and then comes the need to have congestion management in place and TCP congestion management is window bases which means it adjust the window size to adapt the congestion, and here window size means number of packets and ack in transit or enqueued.Now if its sending packets over an idle network the RTT will be RTTnoload and time each spends in queue is RTT-RTTnoload and hence number of packets will be windowsize*(RTT-RTTnoload) and these packtes sits at the router at the head of bottleneck link.Now if the TCP congestion management is in such as way to equally share the link between tow connections this means the realized throughput will fall 45 deg arrow from the origin. and in ideal situations sum of two throughputs be equal to R and hence our goal is to reach a throughput which fall near to intersection of equal bandwidth share line and the full bandwidth line.

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