UDP vs. TCP distribution [was: Re: [e2e] Can feedback be generated...]
simon at limmat.switch.ch
Fri Mar 2 12:48:03 PST 2001
>>>>> "dpr" == David P Reed <dpreed at reed.com> writes:
> At 09:12 AM 3/2/01 -0800, Sally Floyd wrote:
>> I would be particularly interested if anyone's measurements ever
>> indicated a surge of non-congestion-controlled traffic in the
> Good idea, but I'd caution people to observe that non-TCP traffic is
> still capable of congestion control. For example, one can do
> streaming media over UDP with congestion control - the same signals
> (lost packets, RED, and ECN) can be used to reflect congestion to
> the endpoints and implement a closed-loop adaptive solution (for
> video, lowering frame rate, and prioritizing audio, for example).
...or giving up out of frustration, or getting kicked out of a game.
The thing that comes closest to incapable of congestion control is
probably DNS (except zone transfers). But in terms of bytes, DNS
makes up only ~0.3% of all traffic around here (even though we have a
couple of ccTLD servers on our network).
Unfortunately I cannot look at the "UDP-other" traffic (~90% of UDP
traffic or 2.7% of all bytes) very well. I'd venture a guess that
most of this is RealMedia/QuickTime/Windows Media Player. Those
should use fairly well-defined congestion control mechanisms. Is
there any work on characterizing these kinds of transport protocols
with respect to their levels of "TCP-friendliness"?
> So the actual detection and measurement of "non-congestion-controlled"
> traffic flows is an end-to-end issue. It isn't strictly observable at
> router, certainly not by just looking at protocol numbers.
More information about the end2end-interest