Middleware 2003

ACM/IFIP/USENIX International Middleware Conference

Rio Othon Palace Hotel

Rio de Janeiro, Brazil

16-20 June 2003

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Full Paper Abstracts

Congestion Control in a Reliable Scalable Message-Oriented Middleware

Peter Pietzuch and Sumeer Bhola (U. of Cambridge and IBM T.J. Watson)

This paper presents congestion control mechanisms for reliable and scalable message-oriented
middleware. We focus on the publish-subscribe communication model, implemented using an
overlay network of brokers. Brokers can perform hop-by-hop filtering of messages on the path from
a publisher to a subscriber, and can cache messages at intermediate hops for satisfying
retransmission requests. We identify the key requirements of congestion control in this environment,
how it differs from congestion control for the Internet, and propose a combination of two congestion
control mechanisms, (1) driven by a publisher hosting broker (PDCC), (2) driven by a subscriber
hosting broker (SDCC). SDCC decouples the notion of a receive window and a NACK window,
and is used by subscriber hosting brokers in recovery mode. PDCC implements a scalable and low
latency feedback loop between a publisher hosting broker and all subscriber hosting brokers, which
is used to adjust the rate of publishing new messages. PDCC normalizes the rate at different
subscriber hosting brokers, regardless of which subset of messages they receive, and handles
recovering brokers in a way that they are guaranteed to eventually complete their recovery phase.
We present a detailed experimental evaluation of our implementation of these mechanisms in the
Gryphon system by injecting network failures and link congestion.

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