[e2e] Why do we need TCP flow control (rwnd)?

Craig Partridge craig at aland.bbn.com
Fri Jul 11 07:05:15 PDT 2008

In message <4E44F683-8AAB-451F-BC39-0ECA9A6F688F at surrey.ac.uk>, Lloyd Wood writ

>On 2 Jul 2008, at 00:56, Fred Baker wrote:
>> The thing that I find a little hard to grasp is why folks might have  
>> thought the network was Poisson in the first place.
>I doubt they did; it was chosen because it made the arithmetic  
>"First, assume a spherical cow..."

I think this is unfair to the legions of statisticians that got
us to making Poisson models work in the first place.

The reason folks thought that data networks would be Poisson was that

    1. Phone networks were demonstrably Poisson

    2. They had nothing else in the arsenal (that is, if you were going
       to do anything non-trivial, you lacked an analytic alternative)

I had long discussions with folks who did statistical modeling in the late
1980s, as it was increasingly clear Poisson was a mistake.  Up to that
point, network traffic was in small enough networks that one could, and
many did, imagine that as the Internet matured, it would start to behave
like the existing big network -- the telephone network.  But the Internet
growth took off and the disparities between what Poisson predicted and
measurements showed became too large to shrug off.  Statistical folks
were deeply puzzled and frustrated.


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