Extending TCP congestion control to multicast

This paper proposes a new single-rate multicast congestion control scheme named PGMTCC, which has been implemented and investigated in PGM. The primary idea of PGMTCC is to extend Sack TCP congestion control mechanism to multicast in order to make multicast perform almost the same as Sack TCP under all kinds of network conditions. To achieve this goal, first of all, the sender should accurately select a receiver with the worst throughput as a representative (acker) by a simplified equation of TCP throughput. Then the Sack TCP congestion control mechanism, with some modifications to be adapted to multicast, is deployed to take charge of congestion control between the sender and the acker. Moreover, in our scheme, the problem of the feedback suppression is considered and solved by a selective suppression mechanism of feedback. NS2 is used to test and investigate the performance of our scheme. As expected, PGMTCC performs almost like Sack TCP under all kinds of conditions. We believe that it is TCP-friendly, robust and scalable.