Large Scale Content Delivery applied to Files and Videos

September 22nd, 2005Reliable multicast is certainly one of the most effective solutions to distribute content, like files andvideos, to a very large number (i.e. possibly millions) of clients. To that respect the ALC and FLUTEprotocols, both coming from the IETF Reliable Multicast Transport (RMT) working group, haverecently been adopted in the context of 3G cellular networks in 3GPP/MBMS and for DVB-H IPDatacast services.This work focuses on reliable multicast with massive scalability as a core requirement, and it buildsupon the RMT IETF solutions. These reliable multicast protocols rely on several building blocks thatwe investigate in detail:* Forward Error Correction (FEC) Building Block: We examine the broad class of "Low DensityParity Check" (LDPC) large block FEC codes. We design derivates, namely LDGM-Staircaseand LDGM-Triangle, and benchmark these codes in detail with respect to their error correctingcapacities, memory requirements and decoding/encoding speeds, and compare them to the ReedSolomon small block code. We found that LDPC codes and their implementation have verypromising performance, especially when used with large files.The FEC building block must be adapted to the channel, and we experimentally evaluate howto best schedule packets, and derive some recommendations.Finally, we analyze the codes with respect to their ability to offer a partial reliability service,i.e. their ability to decode parts of the content even if the whole decoding process cannot finishbecause too many packet are missing. This study leads to quite surprising results.* Congestion Control Building Block: We look at the startup behavior of the three congestioncontrol protocols RLC, FLID-SL and WEBRC.We show that the startup phase of these protocolssignificantly impacts the performance of a file download application.This thesis has also several contributions at application level:* FLUTE extensions: The larger the content, the more e±cient FEC protection is. We thereforepropose a mechanism to aggregate several files in the file delivery protocol FLUTE, and alsoexplain how to logically group files.* Video Streaming: Designing a video streaming solution for an environment having no or aconstrained back channel, due for instance to scalability requirements, leads to many challenges.We introduce the SVSoA version 1 and version 2 approaches, based on ALC. The first onerequires hierarchically encoded videos, while the latter is more adapted to a wireless broadcastuse case and does not need hierarchical encoded videos anymore. These approaches benefitsfrom all the ALC reliable multicast protocols assets in terms of unlimited scalability, congestioncontrol and error recovery.Keywords: Reliable Multicast, FLUTE, ALC, Forward Error Correction (FEC), Low Density ParityCheck (LDPC) Codes, Content DeliveryLe multicast fiable est certainement la solution la plus efficace pour la distribution de contenu via untres grand nombre (potentiellement des millions) de recepteurs. Dans cette perspective les protocolesALC et FLUTE, standardises via l'IETF (RMT WG), ont ete adoptes dans 3GPP/MBMS et dans leDVB-H IP-Datacast dans les contextes des reseaux cellulaires 3G.Ce travail se concentre sur le multicast fiable et a comme requis principal le passage l'echelle massifen terme de nombre de clients. Cette these se base sur les solutions proposees via l'IETF RMT WG.Ces protocoles de multicast fiable sont construit autour de plusieurs briques de base que nous avonsetudie en detail:* La brique Forward Error Correction (FEC) :Nous examinons la classe de codes grands blocs Low Density Parity Check (LDPC). Nous concevonsdes derivees de ces codes, et les analysons en detail. Nous en concluons que les codesLDPC et leur implementation ont des performances tres prometteuses, surtout si ils sont utiliseesavec des fichiers de taille importante.* La brique controle de congestion :Nous examinons le comportement dans la phase de demarrage de trois protocoles de controle decongestion RLC, FLID-SL, WEBRC. Nous demontrons que la phase de demarrage a un grandimpact sur les performances de telechargement.Cette these a aussi plusieurs contributions au niveau applicatif:* Extensions de FLUTE :Nous proposons un mecanisme permettant d'agreger plusieurs fichiers dans le protocole FLUTE.Ceci ameliore les performance de transmission.* Streaming video :Nous proposons SVSoA, une solution de streaming base sur ALC. Cette approche beneficie detout les avantages de ALC en terme de passage a l'echelle, controle de congestion et correctionsd'erreurs.Mots cles : Multicast fiable, FLUTE, ALC, codes correcteur d'erreurs, Forward Error Correction(FEC), Low Density Parity Check (LDPC) Codes, diffusion de conten