[e2e] Historical question: Link layer flow control / silent discard

Detlef Bosau detlef.bosau at web.de
Fri May 24 11:03:36 PDT 2013

Am 24.05.2013 19:48, schrieb Noel Chiappa:
>      > From: Detlef Bosau <detlef.bosau at web.de>
> First, 'flow control' these days is taken to mean 'end-end' - i.e. the
> original source not sending data faster than the ultimate destination can use

That's certainly correct for TCP.

I've not read that much papers on hop to hop flow control - although I 
think it could well make sense.

> it. This has always been handled at the tranport layer - in the case of TCP,

In the case of TCP.
> by the TCP window. Rate control based on the ability of the _network_ to
> carry traffic (which is what you seem to be asking about below) is now
> usually called 'congestion control'.


As you may know, I'm putting a little question mark behind end to end 
congestion control.

> I don't recall how carefully we differentiated between the two back then,
> although I am quite sure we already understood the difference.

No doubt here.

>      > When I read the original catenet work by Cerf, the Catenet employed
>      > link layer flow control.
> I'm not sure that's quite correct: without checking the documents for myself,
> I suspect they would have understood that if the source is connected to
> network A (a fast network), and the next hop is network B (a slow network),
> the link layer flow control on network B would be no use in slowing down the
> host - since it's not connected to network B.
> As I recall, we thought ICMP Source Quench would be the way congestion
> control would be propogated back to the host.

And (this is again history ;-)) why was this abandoned?

(Does anyone happen to recall the reasons?)

Detlef Bosau
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