Bandwidth for High Speed Networks

By using these two assumptions as our starting points

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Unformatted text preview: tion 4. By using these two assumptions as our starting points we are not claiming that they are true, but rather are only looking at the implications if indeed they were true. If one starts with these assumptions then overcoming the complexity problem in achieving fair allocation becomes a vitally important problem. To this end, we propose and examine an architecture and a set of algorithms that allocate bandwidth in an approximately fair manner while allowing the routers on high-speed links to use FIFO queueing and maintain no per- ow state. 1 We use the max-min de nition of fairness 12 which, while not the only possible candidate for fairness, is certainly a reasonable one and, moreover, can be implemented with only local information. In this approach, we identify an island of routers2 and distinguish between the edge and the core of the island. Edge routers compute per- ow rate estimates and label the packets passing through them by inserting these estimates into each packet header. Core routers use FIFO queueing and keep no per- ow state. They employ a probabilistic dropping algorithm that uses the information in the packet labels along with the router's own measurement of the aggregate tra c. The bandwidth allocations within this island of routers are approximately fair. Thus, if this approach were adopted within the high speed interiors of ISP's, and fair allocation mechanisms were adopted for the slower links outside of these high-speed interiors, then approximately fair allocations could be achieved everywhere. However, this approach, like Fair Queueing 7 or RED 9 , still provides bene t if adopted in an incremental fashion, although the incremental adoption must be done on an island-by-island basis, not on a router-by-router basis. We call this approach Core-Stateless Fair Queueing CSFQ since the core routers keep no per- ow state but instead use the state that is carried in the packet labels.3 We describe the details of this approach such as the rate estimation algorithm and the packet dropping algorithm in S...
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