[e2e] Why do we need congestion control?

Fred Baker (fred) fred at cisco.com
Sat Mar 16 19:24:55 PDT 2013

I'll suggest that you look at the minutes from TSVAREA for the arguments and discussion.

The key factor, though, is that RED, which RFC 2309 makes a great point on, has been widely implemented in commercial product from multiple vendors, but because it requires parameterization operationally, has not been not widely turned on.

We now have at least two AQM algorithms on the table that auto-tune.

As such, while the general statement of 2309 is a good one - that we need to implement AQM procedures - the specific one it recommends turned out to not be operationally useful. 

As to the specific statement that Lloyd seeks, and notes that the TCP community argues for one specific answer, I'll note that operationally-deployed TCP has more than one answer. There is Microsoft's Congestion Control algorithm, NewReno in FreeBSD, and CUBIC in Linux. There are other algorithms such as CAIA CDG that also fill the bottleneck in a path but manage to do so without challenging the cliff, which at least in my opinion is a superior model.

Similarly, it is difficult to argue that everyone has to implement the same AQM algorithm. What is reasonable without doubt is that whatever algorithm is implemented, the requirement is that it manage queue depths to a statistically shallow queue.

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