Circuit Breakers for Multimedia Congestion Control

Abstract

Abstract-Real-time multimedia flows comprise a large, and increasing, fraction of the traffic on the Internet. An important subset of that traffic, primarily due to interactive applications, runs over UDP/IP, and requires applications to implement congestion control to ensure the stability of the network. The IETF is developing congestion control algorithms for such uses as part of the new WebRTC standards, but there is no standard algorithm that can be used at this time. We do not propose a congestion control algorithm. Rather, we propose a circuit breaker for RTP sessions that can detect when an application is causing excessive network congestion, and shut down the transmission. This can be used as an envelope within which congestion control algorithms can operate, providing a safety net to prevent congestion collapse. We present the RTP circuit breaker algorithm, and provide an initial performance evaluation to show that it performs as desired.

Media usability circuit breakers for RTP-based interactive networked multimedia

“…Our evaluation of the RTP-CB behaviour contributes to the currently limited experimental assessment of the RTP-CB available in the literature [5]. For sample video sessions (either allowed or terminated by the RTP-CB), we consider the video quality, along with bandwidth usage/share, to assess the effectiveness of the RTP-CB.…”

“…Congestion-controlled RTP flows, and uncontrolled RTP flows in lightly loaded environments, operate without triggering the RTP-CB, while misbehaving flows that cause congestion will be terminated. Evidence in the literature supports the ability of the RTP-CB to prevent persistent severe congestion [5] [6] using the RTP-CB congestion rule of [4]. Alongside this rule, a media usability rule for the RTP-CB has been suggested [4], but to date no algorithm has been proposed to implement it.…”

An evaluation of RTP circuit breaker performance on LTE networks

“…We show that simply reducing the multiplier in the congestion circuit breaker is not sufficient to address this issue, but that using the more complete TCP model of Padhye et al gives better performance. Unfortunately, our previous work [10] has shown that this more complete TCP model leads to an overly sensitive circuit breaker when used in residential access networks. We believe some of this over-sensitivity is due to averaging packet loss events over long RTCP reporting intervals.…”

“…Performance of the circuit breaker on residential access links and for interactive multimedia is studied in [10]. This shows the circuit breaker takes at least 20 s to engage when the reported loss fraction is higher than 33 %, giving time for a congestion control algorithm to operate.…”

“…The RTP circuit breaker is described in detail in [9] but that includes no performance evaluation. Previous work [10] outlines the performance of the circuit breaker in residential networks using trace-driven simulation, but does not consider LTE networks. Ours is the first evaluation of the proposed circuit breaker in LTE networks.…”