[e2e] Codel and Wireless

Detlef Bosau detlef.bosau at web.de
Wed Dec 4 12:26:52 PST 2013

Am 04.12.2013 19:55, schrieb dpreed at reed.com:
> I'd like to understand how web traffic does better on a fully
> congested link.

better than what?
> Is it possible that you define "bufferbloated" to mean that there is
> at least one queue that is very large?

To my understanding, buffer bloat is exactly that.
> If in that case a short "web traffic" queue gets priority, and there
> is minimal physical queueing in the devices that can get filled - that
> would not be "buffer bloated" according to any definition I know of.

When there are no devices that can be filled there is hardly any buffer

> However, identifying "web traffic" (or "game click" traffic) at the
> switch/router level is a serious violation of modularity (sometimes
> called layer violation).  We used to call that a "kludge".
Shall the network offer service to the users? Or shall the network offer
service to the layers?

As you know, Ford & Iyengar put the traditional layer concept in
question.  That does not mean that layers as they are defined are bad.
But that does mean, that layers aren't sacred cows.

Sacred cows are a matter of religion. Not a matter of science.

> And from a technical point of view, on an end-to-end basis, having a
> seriously backed up queue of one class of traffic in the middle of the
> network is never a good idea - it provides no extra throughput, and
> while prioritized traffic is little disturbed, the users of that queue
> are essentially making the network unable to reallocate physical layer
> resources (e.g. the modulated, shared channel).

Fine. So it might make sense to handle different traffic in different ways?

> Why should a queue be longer than 2 packets at any point in the
> network, at any point in time?

I argued several times why in wireless networks some amount of queueing
may make sense.

And I argued, that this is a non trivial issue which requires some

I would be a happier man than I am, when all questions in life could be
sufficiently answered by one simple answer.
And the question you ask is one of the apparently simple questions which
may require a not so simple answer.

Detlef Bosau
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