Informed Content
Delivery Across Adaptive Overlay Networks_
John Byers, Jeffrey Considine
(Boston University) Michael Mitzenmacher (Harvard
University) and Stanislav Rost (MIT) Overlay networks have emerged as a powerful and highly
flexible method for delivering content.
We study how to optimize throughput of large transfers across richly
connected, adaptive overlay networks, focusing on the potential of
collaborative transfers between peers to supplement ongoing downloads. First, we make the case for an erasure-resilient
encoding of the content. Using the
digital fountain encoding approach, end-hosts can efficiently reconstruct the
original content of size n from a subset of any n symbols drawn from a large
universe of encoded symbols. Such an
approach affords reliability and a substantial degree of application-level
flexibility, as it seamlessly accommodates connection migration and parallel
transfers while providing resilience to packet loss. However, since the sets of encoded symbols
acquired by peers during downloads may overlap substantially, care must be
taken to enable them to collaborate effectively. Our main contribution is a collection of
useful algorithmic tools for efficient estimation, summarization, and
approximate reconciliation of sets of symbols between pairs of collaborating
peers, all of which keep message complexity and computation to a
minimum. Through simulations and
experiments on a prototype implementation, we demonstrate the performance
benefits of our informed content delivery mechanisms and how they complement
existing overlay network architectures. Papers are provided as
a service to all by the members of ACM SIGCOMM. This
paper is available in Adobe PDF format. |