Tuesday, May 22, 2007

Iterative Scheduling Algorithms

Iterative Scheduling Algorithms, Mohsen Bayati, Balaki Prabhakar, Devavrat Shah, Mayank Sharma, in Proc. of Infocom'07, Anchorage, May 2007.

A paper where I attended the session at Infocom and made a note to read the document. This is basically a distributed iterative algorithm to schedule the packets to transfer between the input and the output of a switch with no speed up.

The algorithm is an auction algorithm proposed by Bertsekas where the bids are based on the queue length at each input buffer (actually, at each virtual output queue in the input buffer, namely the virtual buffer corresponding to the packets requesting a specific output buffer). The details of the algorithm are not particularly intuitive, a reaction I've had at the presentation itself and reading the paper.

The algorithm enacts a maximum weight matching approximation, which can be arbitrarily good, and the throughput is thus almost optimal. This improves over the previous switch scheduling algorithm (iSLIP in particular).

Anyhow, the reason I was interested was that the algorithm supposedly could be applied to wireless networks. While the result in the paper is extremely valuable, I am disappointed on this count. First, the number of required iterations seems impractical for an actual wireless networks. Second, it is not clear to me who should be participating in the auction algorithm or how. I guess I would need to see a protocol. But the switch allows all inputs and outputs to exchange bids and assignments easily, something that I do not see in the wireless mesh context.


hooligan said...

Hi, you are not updating this blog anymore?

I am waiting for your updates :) Good blog!

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