Video traffic is growing in prominence on the Internet. It is desired to optimize the performance of the Internet for video delivery. Maintaining a small end-to-end delay is a critical factor for acceptable delivery of real time video. The retransmission requests on packet losses, however, can result in significantly large delays which are often unacceptable making the retransmitted packets obsolete for the current playout. By the use of caching at some intermediary routers, the delivery path for video packets upon retransmission requests can be shortened and hence, the retransmission time can be reduced by a significant amount making it feasible for timely redelivery of lost packets. This retransmission time can be further minimized if optimal placement of caching routers is considered.
This thesis presents the detailed analysis on reduction of the retransmission delay for video traffic using video caching routers. The expression for the average retransmission delay is formulated in the presence of video caching routers which is used to define a mathematical program to minimize the average retransmission delay. Finally, a dynamic programming solution is obtained that finds the optimal placement of caching routers in a given network path for video delivery that minimizes the average retransmission delay. The results obtained from the dynamic programming solution are then verified against the experimental exhaustive enumeration performed with a simulation model of the system.
Further, the performance of the optimal caching router placement is analyzed against the worst case cache placement by varying the size of the problem. It is observed that the optimal placement of caching routers reduces the network cost in a significant manner by minimizing the number of caching routers for meeting a desired retransmission delay performance.