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
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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- Fall '10
- Eugene Ng
- Scheduling algorithm, Round-robin scheduling, Scheduling algorithms, Ow, Fair queuing, ows