Laboratoire d'informatique de l'École polytechnique

PhD defense of Mohammed Hawari

Speaker: Mohammed Hawari
Location: Online
Date: Tue, 6 Jul 2021, 09:00 - Fri, 9 Jul 2021, 11:00

Mohammed Hawariwill defend his doctoral thesis for the degree of doctor in Computer Science on Tuesday, July 6th at 9:00 AM (GMT+1). Due to the COVID pandemic, this defense will happen remotely.

This defense will discuss System and Networking Aspects of the Transition of High-Performance Applications from Dedicated to Commodity Hardware: the Example of Media Production for Professional Broadcast.

Abstract: Due to the increasing performance offered by commodity servers and to the general availability of multi-gigabit Ethernet-based networking hardware, a growing number of performance-intensive and network-intensive applications are being migrated from dedicated to commodity hardware. Examples thereof include scientific computing and network-packet processing, historically implemented by dedicated super-computing clusters and by dedicated packet-processing hardware, respectively. However, media production for professional broadcast (i.e., the process by which multiple audiovisual sources are mixed and processed, in real-time, to elaborate the audiovisual stream as it will be consumed by the final viewer) is still being implemented with dedicated hardware equipment, based on the Serial Digital Interface (SDI), an interconnection technology carrying the legacy of analog video. Despite an ongoing industrial effort to replace SDI with IP-based interconnection — as specified by the SMPTE 2022-6 and 2110 standards — the delay-sensitive nature of media production still challenges its total transition to software running on commodity servers. This thesis solves different aspects of that problem.

First, the high rates and low jitter-tolerance of media production packet streams have motivated a quantitative and qualitative study of the sources of jitter undergone by those streams when they are processed by commodity servers. In addition to results specific to Linux x86_64 servers, that work has yielded a general jitter exploration methodology, applicable to any operating system and hardware commodity servers. Second, a generic platform enabling the implementation of custom high-accuracy instrumentation for hardware-based packet timestamping has been developed. By exposing a high-level programming interface — relying on the P4 language — that platform, despite being FPGA-based, allow network and broadcast operators with little hardware design skills to specify custom logic for line-rate packet processing and timestamping. In particular, such instrumentation can be used to qualify the jitter properties of media production streams. Third, a system to perform packet-pacing — i.e., the transmission of a constant-rate packet stream with negligible jitter — has been proposed. By exclusively but cleverly relying on commodity hardware, that work invalidates the common belief according to which software-based media-production is impossible on commodity servers (due to the jitter they introduce). The proposed system has been formally and experimentally proven to yield a jitter, conforming to the requirements of media production streams. Finally, a software framework easing the implementation of media-production applications has been developed. That framework relies on a separation between media processing and media transport: the media processing logic receives and transmits full media frames (e.g., video frames) from the media transport logic, which handles high-performance packet processing with techniques such as zero-copy and kernel bypass networking. Those last techniques have been shown to notably increase the scalability of media production on commodity servers.

Link to the online conference