Abstract-Real-time multimedia comprises a large, and growing, fraction of mobile data traffic. An important subset of such flows are from interactive conferencing applications using RTP on UDP/IP to reduce latency. UDP has no congestion control, and while the IETF is developing RTP-level congestion control algorithms as part of the WebRTC standards, these will take time to finalise and deploy. In the interim, we proposed an RTP circuit breaker to the IETF. This can detect and stop RTP flows that cause excessive network congestion, acting as an envelope within which a congestion control algorithm can operate. We briefly review the design of the RTP circuit breaker, then present an initial evaluation of its performance on LTE networks. Our results show that the algorithm is conservative in overload situations with low delay and high loss. Such situations can occur due to active queue management in LTE networks. We propose changes to the RTP circuit breaker to better suit such networks, by using a different TCP throughput model that is more sensitive to the observed packet loss patterns.
This document describes two reference video traffic source models for evaluating RMCAT candidate algorithms. The first model statistically characterizes the behavior of a live video encoder in response to changing requests on target video rate. The second model is tracedriven, and emulates the encoder output based on actual encoded video frame sizes from a high-resolution test sequence. Both models are designed to strike a balance between simplicity, repeatability, and authenticity in modeling the interactions between a live video traffic source and the congestion control module. Finally, the document describes how both approaches can be combined into a hybrid model. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts.
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