Real-time multimedia applications use either TCP or UDP at the transport layer, yet neither of these protocols offer all of the features required. Deploying a new protocol that does offer these features is made difficult by ossification: firewalls, and other middleboxes, in the network expect TCP or UDP, and block other types of traffic. We present TCP Hollywood, a protocol that is wire-compatible with TCP, while offering an unordered, partially reliable messageoriented transport service that is well suited to multimedia applications. Analytical results show that TCP Hollywood extends the feasibility of using TCP for real-time multimedia applications, by reducing latency and increasing utility. Preliminary evaluations also show that TCP Hollywood is deployable on the public Internet, with safe failure modes. Measurements across all major UK fixed-line and cellular networks validate the possibility of deployment.

Abstract-Ossification of the transport-layer limits networked multimedia applications to use TCP or UDP, despite standardisation of new transport protocols that better support their requirements. To improve transport for these applications, we present TCP Hollywood, an unordered, time-lined, TCP variant designed to support real-time multimedia traffic while being widely deployable. Analysis of the protocol indicates that it increases the utility of the network in lossy conditions where total one-way delay is constrained, such as with telephony applications and low-latency video streaming. This allows retransmissions to be useful in cases where they are not with standard TCP, improving the timely good-put of the protocol and reducing overheads. Initial experiments show that TCP Hollywood is deployable on the Internet, successfully operating on all major fixed and mobile networks in the UK, with safe failure modes.

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.

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Anycast is a popular tool for deploying global, widely available systems, including DNS infrastructure and content delivery networks (CDNs). The optimization of these networks often focuses on the deployment and management of anycast sites. However, such approaches fail to consider one of the primary configurations of a large anycast network: the set of networks that receive anycast announcements at each site (i.e., an announcement configuration). Altering these configurations, even without the deployment of additional sites, can have profound impacts on both anycast site selection and round-trip times. In this study, we explore the operation and optimization of anycast networks through the lens of deployments that have a large number of upstream service providers. We demonstrate that these many-provider anycast networks exhibit fundamentally different properties when interacting with the Internet, having a greater number of single AS hop paths and reduced dependency on each provider, compared with few-provider networks. We further examine the impact of announcement configuration changes, demonstrating that in nearly 30% of vantage point groups, round-trip time performance can be improved by more than 25%, solely by manipulating which providers receive anycast announcements. Finally, we propose DailyCatch, an empirical measurement methodology for testing and validating announcement configuration changes, and demonstrate its ability to influence user-experienced performance on a global anycast CDN.