[e2e] Why Buffering?

Dave CROCKER dhc2 at dcrocker.net
Fri Jun 19 21:23:04 PDT 2009

Paddy Ganti wrote:
> The real reason for having buffers is the fact that information about
> congestions takes some time to propagate. (In TCP/IP congestion are
> detected by seeing lost packets).

In the late 70s and 80s, Kleinrock gave a rather simple explanation for using 
queuing (buffering) that I think is compatible with Antonov's point:

      After a lengthy and detailed introduction, he put up a graph of throughput 
(x) versus delay (y).  It had a very shallow increase until hitting a very sharp 
knee and then was almost vertical.

      He observed that before the knee, you don't need queuing because you don't 
have any congestion.  And after the knee, queuing doesn't help because you 
simply don't have enough capacity.

Queuing is for transient problems rather than an excessive average:  The knee of 
the curve.



   Dave Crocker
   Brandenburg InternetWorking

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