‘Control plane’ properties for signaling in loss-feedback based video rate adaptation over shared multicast paths

In wide-area video conferencing, the rate control of video sources to relieve network congestion along the multicast data path occurs in a distributed manner. In this paper, we study the desirable properties of signaling channels that carry the `packet loss report´ (ELR) from a receiver to the sources as a short control message. A signaling channel provides for loss-free and time-ordered flow of ELRs from receivers, so that the rate adjustments of sources triggered by the signaling messages are executed correctly. For instance, the loss of a ELR may delay the source-level response to relieve congestion. Our goal is to improve the quality of rate adaptation when relieving congestion along the video data paths, with a suitably constructed ELR-signaling channel. For this purpose, we employ a group communication substrate, SINS, that provides loss-free and time-ordered message flows based on Lamport´s concept of global virtual time. The paper demonstrates improvements in the quality of adaptation during congestion relief: faster convergence to final send rates and lower rate oscillations.