This paper introduces Wave and Equation Based Rate Control (WEBRC), the first multiple rate multicast congestion control protocol to be equation based. The equation-based approach enforces fairness to TCP with the benefit that fluctuations in the flow rate are small in comparison to TCP.This paper also introduces the multicast round trip time (MRTT), a multicast analogue of the unicast round trip time (RTT). The MRTT is fundamental to the equation-based protocol that each receiver uses to adjust its reception rate. Each receiver independently measures its own MRTT without placing any added messaging burden on the receiver, the sender or the intermediate network elements. Benefits provided by the MRTT include those that the RTT provides to TCP, e.g., reduced reception rates in reaction to buffer filling and fair sharing of bottleneck links. In addition, the use of MRTT is shown to synchronize and equalize the reception rates of proximate receivers and to cause reception rates to increase as the density of receivers increases.Another innovation of WEBRC is the idea of transmitting data with waves: the transmission rate on a channel is periodic, with an exponentially decreasing form during an active period followed by a quiescent period. Benefits of using waves include insensitivity to large IGMP leave latency; a frequency of joins and leaves by each receiver that is small and independent of the receiver reception rate; the use of a small number of multicast channels; fine-grained control over the receiver reception rate; and minimal, at times nonexistent, losses due to buffer overflow.

We describe fair layered increase/decrease with dynamic layering (FLID-DL): a new multirate congestion control algorithm for layered multicast sessions. FLID-DL generalizes the receiver-driven layered congestion control protocol (RLC) introduced by Vicisano et al. (Proc. IEEE INFOCOM, San Francisco, CA, , p.996-1003, Mar. 1998)ameliorating the problems associated with large Internet group management protocol (IGMP) leave latencies and abrupt rate increases. Like RLC, FLID-DL, is a scalable, receiver-driven congestion control mechanism in which receivers add layers at sender-initiated synchronization points and leave layers when they experience congestion. FLID-DL congestion control coexists with transmission control protocol (TCP) flows as well as other FLID-DL sessions and supports general rates on the different multicast layers. We demonstrate via simulations that our congestion control scheme exhibits better fairness properties and provides better throughput than previous methods. A key contribution that enables FLID-DL and may be useful elsewhere is dynamic layering (DL), which mitigates the negative impact of long IGMP leave latencies and eliminates the need for probe intervals present in RLC. We use DL to respond to congestion much faster than IGMP leave operations, which have proven to be a bottleneck in practice for prior work.