[e2e] a new IRTF group on Transport Models

David P. Reed dpreed at reed.com
Tue Jun 7 12:02:32 PDT 2005

Clark Gaylord wrote:

> as example: corruption could be cell loss.  cell loss could be due to 
> congestion.

Interesting... by blurring the concept of "cell congestion" together 
with "router congestion" you end up with a confused description of the 

TCP is based on a model where datagrams get through or they don't.   
That's the IP model.

The engineering approach is to force all situations into those two 
cases.   Enhancing TCP or replacing it would be possible if the possible 
outputs that result from a sequence of inputs could be characterized, 
and doable if the characterization has some predictable structure.

If you try to design an end-to-end protocol where the inputs map to 
arbitrary outputs (any causal output stream-generating process that can 
be computed by a finite physical apparatus is as likely as any other), I 
doubt you will succed.

This is ultimately why we put "cell-based links" into a modular black 
box that doesn't try to expose the cell structure of a datagram to the 

It's also why we normally use the "digital abstraction" instead of 
modeling digital computers as analog machines.  One could do 
otherwise.   One could even argue that it would be more "efficient" for 
some meaning of the term efficiency.

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