[e2e] Why do we need congestion control?

Jon Crowcroft Jon.Crowcroft at cl.cam.ac.uk
Sat Apr 6 03:56:03 PDT 2013

In missive <515FFA56.7060200 at web.de>, Detlef Bosau typed:

 >>>>  Manu, how do you want to implement fair queueing on a backbone router
 >>> First, I've never claimed that I wanted to implement such mechanism=20
 >>> inside the core router.

 >>I see. Howver: To my understanding, fair queueing must be available on=20
 >>any router in this approach?

not necessarily - see Core Stateless Fair Queueing

 >>>> with actually 200.000 flows? 150.000 of them being "mice"?
 >>> You talk on average not instantaneously. You only maintain a state for=20
 >>> flows currently enqueued.
 >>> It means that if you have a queue size of 30 packets, you can't have=20
 >>> more than 30 states in your table.
 >>>>  At least this question should be discussed for both kind of
 >>>> approaches, VJCC and DTCP.
 >>> It has been already discussed for TCP, just google FairDrop and TCP.
 >>>>  So to my understanding, neither VJCC nor DTCP separates the problem
 >>>> of resource allocation from the problem of congestion control, nor do
 >>>> they eventually _solve_ the problem of (fair) resource allocation.
 >>> Anyway, my ISP with CAC or DiffServ does?
 >>Do we talk about fair queueing in the sense of best effort? The problem=20
 >>to find the right trade off between a more or less uncontrolled system=20
 >>and a QoS system here. CAC and DiffServ are clearly on the QoS side.
 >>Detlef Bosau
 >>Galileistra=C3=9Fe 30
 >>70565 Stuttgart                            Tel.:   +49 711 5208031
 >>                                            mobile: +49 172 6819937
 >>                                            skype:     detlef.bosau
 >>                                            ICQ:          566129673
 >>detlef.bosau at web.de                     http://www.detlef-bosau.de



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