Re: Good qdisc for routers?

[Dennis Jacobfeuerborn <dennisml@conversis.de>]

On 05.11.2013 19:06, Remy Mudingay wrote:
> Hi Dennis,
>
> I  highly recommend trying out codel or fq_codel. I've been using
> fq_codel for well over a year now. I have just over a thousand users
> going through the router. I use it mainly because I wanted in-queue
> packet delays statistics but I didn't switch from pfifo_fast because of
> any perceived problems.
> Anyway, You won't need to patch your current Linux install as long as
> it's version 3.3 or higher.
>
> I use the following two lines for each interface.
>
> tc qdisc add dev eth0 root handle 1: fq_codel quantum 1514 flows 1024 noecn
> tc filter add dev eth0 prio 1 protocol all parent 1: handle 1 flow hash
> keys nfct-src,nfct-dst,nfct-proto,nfct-proto-src,nfct-proto-dst divisor
> 10242 perturb 300 baseclass 1:1
>
> You can get more in depth information from here
> http://www.bufferbloat.net/projects/codel/wiki.

Codel seems more geared towards low latency. The following statement 
from the wiki doesn't make it sound like this is the right choice here:

"People have tried to run CoDel in very big routers, with hundreds of 
simultaneous flows, a situation not simulated in advance. There, it 
isn't controlling the queue the way it should: whether this is a problem 
with the algorithm, or the implementation, is not yet understood.

It is clear that unmodified, CoDel is not appropriate for AQM of traffic 
inside a data center; it does not react in a timely enough fashion. 
Whether the modifications of the ideas in CoDel will solve this problem 
is not yet known. Again, this is an area which CoDel was not designed to 
solve or it simulated in before publication."

Regards,
   Dennis