[e2e] Congestion control as a hot topic in IETF

[Detlef Bosau]

Am 04.03.2013 23:07, schrieb Scharf, Michael (Michael):
> There has been some interesting research on whether a transport protocol could work without any congestion control. One reference is: B. Raghavan and A. Snoeren, "Decongestion Control", ACM SIGCOMM Workshop on Hot Topics in Networks, 2006.
>
I remember that you, some years ago, asked whether networking can be 
done without flow control.

O.k. I just asked my provider to give me some additional space for my 
mailbox and claim the following:

Congestion control is necessary, because when God created cabling and 
fibre, he forgot to give them a mouth to talk.
So, we actually don't know how much data can reside, if transient, on 
the line. And NB: This is anything else but a trivial question.
Particularly on mobile networks, we have only little knowledge about the 
transient channel capacity (you might remember some personal discussions 
between us two about 8, 9 years ago), if at all. The same holds true for 
shared networks e.g. Ethernet, particularly the good old yellow garden hose.

So, actually, the only way to assess whether the amount of  data send to 
a "media" stays within "acceptable limits" is, simply spoken, trial and 
error.
Either it fits - or it is dropped.

Depending on the link technology in use, this situation may vary. 
However, the fundamental problem is generic.

While receivers can talk, perhaps God spent more time in creating them, 
flow control is easier.

Congestion control is achieved indirectly and - to make things worse - 
it is strongly intertwined with scheduling.

Particularly, VJCC attempts to extend TCP's "self clocking" into a "self 
scheduling" which is cumbersome because self scheduling requires 
sufficient space for the data to be interleaved to be put. I strongly 
suspect that the latter is a sufficient reason for what we often call 
"buffer bloat".


Detlef

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