Cross-Protocol Unfairness between Adaptive Streaming Clients over HTTP/3 and HTTP/2: A Root-Cause Analysis

Abstract

With the introduction of HTTP/3, whose transport is no longer the traditional TCP protocol but the novel QUIC protocol, research for solutions to the unfairness of Adaptive Streaming over HTTP (HAS) has become more challenging. In other words, because of different transport layers, the HTTP/3 may not be available for some networks and the clients have to use HTTP/2 for their HAS applications instead. Therefore, the scenario in which HAS over HTTP/3 (HAS/3) competes against HTTP/2 (HAS/2) must be considered seriously. However, there has been a shortage of investigations on the performance and the origin of the unfairness in such a cross-protocol scenario in order to produce proper solutions. Therefore, this paper provides a performance evaluation and root-cause analysis of the cross-protocol unfairness between HAS/3 and HAS/2. It is concluded that, due to differences in the congestion control mechanisms of QUIC and TCP, HAS/3 clients obtain larger congestion windows, thus requesting higher video bitrates than HAS/2. As the problem lies in the transport layer, existing client-side ABR-based solutions for the unfairness from the application layer may perform suboptimally for the cross-protocol case.

Sprinkle Prebuffer Strategy to Improve Quality of Experience with Less Data Wastage in Short-Form Video Streaming

“…It is speculated that such a phenomenon was related to the differences in the congestion control mechanism between the transport layer of HTTP/2 and HTTP/3. It has been reported that the transport QUIC [45] of HTTP/3 updates the congestion window more frequently and increases it more aggressively than TCP [46] of HTTP/2, therefore utilizing the bandwidth better [34]. Thus, there was no unusual bandwidth deterioration occurring when using HTTP/3 as shown in Figure 12b.…”

“…On the other hand, it is possible to consider the use of the novel HTTP/3 protocol [41]. Specifically, existing research has found that HTTP/3 brought effective boosts for the user's QoE in long-form video streaming [34,42], especially for the case of the mobile network [43,44]. Yet, no research has ever investigated the similar impact of HTTP/3 on neither the QoE nor data wastage in short video streaming.…”

“…Both mobile network slices were obtained from the real mobile network trace in [33] and their bandwidth histograms are shown in Figure 5. The experiment was set up similar to that in [34]. Both the streaming server and the client were virtual machines running Ubuntu 20.04 LTS with 4 GB of RAM.…”