[Codel] fq_Codel vs Sfq_Codel

Tom Henderson tomh at tomh.org
Sat Feb 28 18:36:04 EST 2015

On 02/28/2015 09:58 AM, Dave Taht wrote:
> sfq_codel in ns2 is derived more from SFQ than DRR, and there are
> several substantial differences, although sfq_codel  can be almost,
> but not quite, configured to act the same as the dual DRR version that
> is in the actual, shipping, fq_codel. The version of DRR fq_codel uses
> is more similar to "DRR+" and "DRR++", but is uniquely it's own.
> You have to use sfq_codel VERY carefully in the ns2 version, as the
> ability to correctly generate a five tuple hash is not there.
> Correctly generating a 5 tuple is almost, but not quite, in the ns3
> version, last I looked, and that ns3 version is MUCH closer to the
> actual fq_codel version deployed in the field, but still not quite the
> same thing.  I have kind of lost track as to the right ns2 and ns3
> versions to start from, also. Tom?

Dave and all,

The status of ns-2 and ns-3 support is as follows.

In ns-2, some new models (CoDel, SFQCoDel, CoDel-DT, and PIE) 
contributed by Kathleen Nichols, CableLabs, and Cisco will be part of 
the ns-2.36 release, which is in preparation.  An initial release 
candidate was posted here:

and the code in the CVS tree is consistent with this.  (Preview) 
documentation on the new models is available here:
and here:

When will 2.36 be released?  I am working through a long list of issues 
getting the debug build to work on clang-based systems, and when those 
are resolved (in the next few weeks?) I'll release 2.36.  The release 
candidate above is pretty close to what will be the final bits.

In ns-3, basic CoDel was added in n-3.21.  Dave and Andrew McGregor 
contributed some models for FQ- and SFQ-CoDel a while back; links to 
this code can be found on our wiki Current Development page.  Inclusion 
of these is blocked by some stack refactoring that Dave pointed to in a 
subsequent post, to insert a priority queue sublayer for these queues. 
I'm working towards the goal of making these available by ns-3.23 (May), 
but I aimed for ns-3.22 and missed, so I can't promise that these will 
be done by May; we'll see.

If anyone wants to help test these new simulation models and get them 
into shape for release, please contact me.

- Tom

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