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David Mulveney "Core-Stateless Fair Queueing: Achieving Approximately Fair Bandwidth Allocations in High Speed

Summary: David Mulveney
"Core-Stateless Fair Queueing: Achieving Approximately Fair Bandwidth Allocations in High Speed
The key point of this paper is developing a new method for queueing packets in routers and making
sure different flows only receive their fair share of the available bandwidth. This is accomplished by having
edge routers in the Internet do some processing on each packet to put identifiers into the header giving a
probability the packet should be dropped if it encounters a congested link. This probability is determined by
the rate packets arrive and the available bandwidth in the link.
This approach performs well under most circumstances. CSFQ has a few problems when it comes to
bursty traffic as shown in the ON-OFF traffic model experiment. Under this experiment CSFQ does not
perform as well as FRED because it allows for a larger average queue size and therefore allows for more
congestion in intermediate links. Another problem addressed in the paper is if edge routers put incorrect
information into their packets. If the rate put in by a router is more than the actual rate CSFQ will drop that
flows packets more often when they encounter congestion, but if the rate inserted into the packet is less than
the actual rate the flow will get more bandwidth than it is supposed to. After some time CSFQ will realize that
this misbehaving flow is sending more traffic than it says it is and CSFQ will eventually realize this and drop
the flow's available bandwidth to correct the error. Based on this it is evident that CSFQ can be fooled to
send extra traffic for short bursts, but it corrects the allocations after time.
There are some interesting clean slate ideas presented in this paper. It starts by using the idea of a bit
stream abstraction for the traffic flowing through a link. The basis of the protocol is from this idea, using a


Source: Akella, Aditya - Department of Computer Sciences, University of Wisconsin at Madison


Collections: Computer Technologies and Information Sciences