[e2e] Are we doing sliding window in the Internet?

David P. Reed dpreed at reed.com
Mon Jan 7 07:22:29 PST 2008

Lars - I'm always interested in learning new things.   Such an attempt 
would be fruitful - I have been wrong in the past, and can admit I am 
wrong.   Sorry if my expression of general frustration with the 
sociology of the IETF and research communities was too "hot-headed".  If 
I had stated it in less spicy terms, there would still be a strong 
argument that others could choose to rebut.

It was not triggered specifically by any one person's views - more an 
integration of a set of views that have been bugging me for years.  
Which is why I did not include any quoted text.

Perhaps my spiciness discourages discussion.  I would hope it would do 
the opposite, perhaps encouraging people to marshal real arguments, real 
data to disprove what I argue for.

Lars Eggert wrote:
> Hi, David,
> since your message has me in the "To" field, I'm guessing it was 
> triggered by one of my earlier emails.
> If that's the case, either I'm not expressing my points clearly 
> enough, or you're significantly over-interpreting them. Or both. 
> Usually, I'd try to clarify things at this point, but reading the rest 
> of your email somehow doesn't leave me with the impression that such 
> an attempt would be fruitful.
> Lars
> On 2008-1-7, at 16:46, ext David P. Reed wrote:
>> 99% of the effect of the original TCP congestion control "innovation" 
>> was due to a simple and robust principle: when a packet is lost, cut 
>> the traffic being sent *drastically*.   This converted a tendency of 
>> the community to turn packet losses into a positive feedback loop of 
>> retransmission into a shared understanding that "positive feedback 
>> loops are bad".
>> That was a community-scale learning that was useful.
>> I would argue that the idea that TCP is now "near perfect" as a 
>> standard that *must be enforced lest the Internet enter congestion 
>> collapse* has almost no real-world evidence.
>> In fact, very little of the traffic on the network today comes in the 
>> form of end-to-end unbounded-rate-demanding streams.   TCP's 
>> congestion control (and the definition of "TCP compatible" fairness, 
>> too!) is "tested" only for such a trivial case.   No One At All tests 
>> TCP congestion control in a world of HTTP, VoIP, streaming video from 
>> YouTube, Skype, etc. The "gurus" of the IETF that study protocol 
>> *documents* have intuitions that are seriously flawed, if only 
>> because they don't actually have any data about the traffic ANYWHERE 
>> in the damn network.   (kc claffy would die to have such data).
>> So it seems that a bunch of self-elected high-priests of IETF have 
>> taken it upon themselves to claim God-like, experiment-free knowledge 
>> of the Internet as it really is, and to use that knowledge to claim 
>> that TCP is the Gold Standard that must be obeyed lest the network 
>> finally do what Bob Metcalfe erroneously said it would do and ate 
>> whatever piece of clothing he ate as a result.
>> Do science and real engineering, please.   Yeah, the AIMD algorithm 
>> in TCP saved the Internet's ass.  But it is not Holy Writ.

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