AIMD with coupon mechanism

The increasing demand of multimedia applications has spurred recent interest in end-to-end congestion control for real-time applications. However, all these mechanisms proposed so far try to provide smooth sending rate and be friendly to TCP. They have paid little attention to the characteristics that distinguish a real-time application from a non-real-time service. The works on equal and unequal protection multimedia transmission through FEC (forward error correction) encoding show that, there are many different structures in an encoded multimedia stream with different importance in the media restoration. In order to protect these different structures of different importance in the transport layer instead of in application layer through FEC a coupon based AIMD (CAIMD, coupon based additive-increase multiplicative-decrease) algorithm is proposed in this paper. In this algorithm, a coupon is attached to each sending packet to indicate the importance of the message carried in this packet. The network services packets differently according to the coupon value attached on them. In order to make CAIMD TCP friendly, the "linear" increase slope in CAIMD is dynamically changed with the importance of the message carried in a sending packet. Theoretical analysis and simulations carried in this paper show that CAIMD is capable of providing different protection in the packet level with a fine granularity, which opens a new means to optimize the QoS of media streams in network transportation. In additional, CAIMD is friendly to TCP flow as well.