Large Scale Content Delivery applied to Files and Videos

Christoph Neumann 1
1 PLANETE - Protocols and applications for the Internet
Inria Grenoble - Rhône-Alpes, CRISAM - Inria Sophia Antipolis - Méditerranée
Abstract : Reliable multicast is certainly one of the most effective solutions to distribute content, like files and
videos, to a very large number (i.e. possibly millions) of clients. To that respect the ALC and FLUTE
protocols, both coming from the IETF Reliable Multicast Transport (RMT) working group, have
recently been adopted in the context of 3G cellular networks in 3GPP/MBMS and for DVB-H IP
Datacast services.
This work focuses on reliable multicast with massive scalability as a core requirement, and it builds
upon the RMT IETF solutions. These reliable multicast protocols rely on several building blocks that
we investigate in detail:
* Forward Error Correction (FEC) Building Block: We examine the broad class of "Low Density
Parity Check" (LDPC) large block FEC codes. We design derivates, namely LDGM-Staircase
and LDGM-Triangle, and benchmark these codes in detail with respect to their error correcting
capacities, memory requirements and decoding/encoding speeds, and compare them to the Reed
Solomon small block code. We found that LDPC codes and their implementation have very
promising performance, especially when used with large files.
The FEC building block must be adapted to the channel, and we experimentally evaluate how
to 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 finish
because 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 congestion
control protocols RLC, FLID-SL and WEBRC.We show that the startup phase of these protocols
significantly 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 therefore
propose a mechanism to aggregate several files in the file delivery protocol FLUTE, and also
explain how to logically group files.
* Video Streaming: Designing a video streaming solution for an environment having no or a
constrained 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 one
requires hierarchically encoded videos, while the latter is more adapted to a wireless broadcast
use case and does not need hierarchical encoded videos anymore. These approaches benefits
from all the ALC reliable multicast protocols assets in terms of unlimited scalability, congestion
control and error recovery.

Keywords: Reliable Multicast, FLUTE, ALC, Forward Error Correction (FEC), Low Density Parity
Check (LDPC) Codes, Content Delivery
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Submitted on : Thursday, January 19, 2006 - 4:19:34 PM
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Christoph Neumann. Large Scale Content Delivery applied to Files and Videos. Networking and Internet Architecture [cs.NI]. Université Joseph-Fourier - Grenoble I, 2005. English. ⟨tel-00011424⟩

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