[ovs-dev] MPLS and VLAN QinQ patch

[Ben Pfaff]

On Thu, May 24, 2012 at 07:25:52PM +0200, Ravi.Kerur at telekom.com wrote:
> > As for the TTL, I don't think that any OpenFlow version allows for
> > matching on an IP TTL, so there is no support-by-analogy for
> > matching on the MPLS TTL.  Is there another reason to support
> > matching on the MPLS TTL?
> 
> I see there is a capability to match on nw_ttl so thought it would
> make sense to add a match for mpls_ttl.

nw_ttl is part of the kernel-to-user interface but it is not exposed
via OpenFlow.  I think that the same is true of the TTL in your MPLS
patch?

> When IP packets traverse MPLS tunnels, IP TTL is copied into MPLS
> TTL and it is copied back into IP when they exit. Hence thought of
> providing a match for that.

Maybe that is enough to make a case for an OpenFlow MPLS TTL match,
but I don't follow.  You might have to spell out the use case
step-by-step for me to understand.

> > > > It occurs to me that we could drop the NXAST_SET_MPLS_LABEL and 
> > > > NXAST_SET_MPLS_TC actions because these can be implemented through 
> > > > "register load" actions.  OpenFlow 1.2 also dropped the similar 
> > > > OFPAT_ actions, for the same reason, so maybe we shouldn't bother 
> > > > with NXAST_ actions for them as they don't have any additional 
> > > > benefit for OpenFlow 1.0 with Nicira extensions.
> > > 
> > > Same argument as above. In this case it isn't quite clear to me how 
> > > set_mpls_label and set_mpls_tc be implemented via reg_load. Any 
> > > pointers?
> > 
> > In ovs-ofctl syntax, the "load" actions would look like this:
> >         load:123->NXM_OF_MPLS_TC[]
> >         load:5->NXM_OF_MPLS_LABEL[]
> > 
> Thanks for the information. I will work on it after 1.1 is ready.

I doubt you need to take any action to make this work.  It should
"just work" without any further changes.

Thanks,

Ben.