These are the old pages from the weblog as they were published at Cornell. Visit for up-to-date entries.

June 19, 2003

Day 2 at Middleware 2003 - session 1

The session was on pub/sub systems

The first talk by Yuan Chen from Georgia Tech was on opportunistic even delivery for pub/sub systems for mobile users. He presented pub/sub system with many features including dynamically instantiating new brokers and other components based on resource uses monitoring. One of these features is a component that implements a subscriber hand-off protocol between brokers to facilitate mobility

The second presentation was by Peter Pietzuch from Cambridge on congestion control for pub/sub systems that he had done as a intern in the Gryphon group at IBM. The problem is how to provide end-to-end as well as broker to publisher flow control based on congestion trigger. The solution they pick is to use an additive/multiplicative increase/decrease scheme based on congestion indications from different components. This is similar to ATM VBR congestion control, but is more complex because of the possibility of congestion indication explosion as the stream basically is a multicast. For the subscriber based flow control they manipulate the acknowledgement streams from the subscribers to the publishers. There are some interesting details in the paper on the way that gryphon observes and manages streams,

The 3rd paper was a carry over from yesterday's P2P systems and detailed techniques for keyword search on DHT based networks by Patrick Reynolds from Duke. He distributes the keyword index over the various nodes in the network and uses a number of optimizations to improve the performance. For an "x and y" style query the 'x' query results in a bloom filter for the document ID's which is sent along with the y query. This allows the node holding the index to filter its result. Other optimizations dealt with caching, and inserting multiple nodes in the DHT.

Posted by Werner Vogels at June 19, 2003 10:20 AM