[frr] 2 MPLS Questions

Jeff Tantsura jefftant at gmail.com
Thu Mar 23 13:21:25 EDT 2017


while on topic, can I please get an API to query data plane for MSD supported?
Use case: draft-ietf-isis-segment-routing-msd/ draft-ietf-ospf-segment-routing-msd/ draft-tantsura-idr-bgp-ls-segment-routing-msd

Many thanks!

Cheers,
Jeff


> On Mar 23, 2017, at 10:07, Vincent Jardin <vincent.jardin at 6wind.com> wrote:
> 
> +Jeff
> 
> 
> Le 23 mars 2017 5:59:21 PM Amine Kherbouche <amine.kherbouche at 6wind.com> a écrit :
> 
> > Hi David,
> >
> > I think that 8 stacked labels are more than enough, I cannot imagine a core
> > network with 8 stacked MPLS-VPNs.
> > Let's see the others if they share my opinions.
> 
> 
> 
> I think too that 8 is a good upper limit.
> 
> 
> >
> >
> > Regards,
> > Amine
> >
> > On 23 March 2017 at 17:47, David Ahern <dsa at cumulusnetworks.com> wrote:
> >
> >> I have the MPLS code changes to bump the number of labels. What did we
> >> want to use for the max? 12? 16?
> >>
> >> This limit is really only capping what we take from userspace. Kernel
> >> side memory allocations are done based on the actual number of labels in
> >> the route.
> >>
> >>
> >> On 3/16/17 10:49 AM, Olivier Dugeon wrote:
> >> > Hi David,
> >> >
> >> > Well, frankly speaking, I don't see where is the problem regarding the
> >> > performance.
> >> >
> >> > IMHO, the patch add an extra size of the array i.e. from 8 bytes (2
> >> > labels) to 64 bytes (16 labels) which is completely negligible compared
> >> > to the size of a IP packet, and of same magnitude order as a VxLan
> >> > encapsulation and twice less as an IPv6 header.
> >> >
> >> > In addition, only the edge router as to push the label stack. Then,
> >> > subsequent router just look at the top label. So, no more no less that a
> >> > packet with only 2 labels in the stack.
> >> >
> >> > I think that dealing with a dynamic MPLS STACK DEPTH i.e. dynamic memory
> >> > allocation of space regarding the number of labels are push in from of
> >> > the IP packet will certainly add more overhead and more CPU cycles
> >> > rather than just manage a fix amount of byte in an array.
> >> >
> >> > Finally, the default value for the MPLS_LABEL_STACK could be equal to 2
> >> > and let peoples want to deal with Segment Routing recompile the kernel
> >> > with a larger value.
> >> >
> >> > From my side, your patch will not only increase the label stack, it also
> >> > re-arrange the MPLS structure in order to solve the problem of corrupted
> >> > third label. And, this is the more important things.
> >> >
> >> > In any case, let me know what I can do to help you.
> >> >
> >> > Regards
> >> >
> >> > Olivier
> >> >
> >> >
> >> > Le 16/03/2017 à 16:10, David Ahern a écrit :
> >> >> I made the kernel patch to help you move along with your MPLS work.
> >> >>
> >> >> In the kernel thread discussing the increase in number of labels Eric
> >> >> Biederman mentions performance concerns about just increasing the size
> >> >> of the array; he wanted a much more complicated change and I have not
> >> >> gotten around to it.
> >> >>
> >> >>
> >> >> On 3/16/17 3:31 AM, Olivier Dugeon wrote:
> >> >>> Hi all,
> >> >>>
> >> >>> The problem is not between the kernel and iproute2. The problem comes
> >> >>> when stacking more than 2 labels: the LSB byte of the third label is
> >> >>> replaced by 0x03 value i.e. the implicit Null Label value. See attached
> >> >>> thread.
> >> >>>
> >> >>> Following this, David propose a new patch that we integrated and tested
> >> >>> successfully (See second and third attached mail).
> >> >>>
> >> >>> But, after that, I got no news and never seen this patch merge into the
> >> >>> Linux Kernel release. So, we just ask when this patch could be merge
> >> >>> into the Linux Kernel.
> >> >>>
> >> >>> For the second problem about PHP, it is also described in the first
> >> >>> attached thread. But, agree, that this issue is more tricking to solve.
> >> >>>
> >> >>> Regards,
> >> >>>
> >> >>> Olivier
> >> >>>
> >> >>>
> >> >>> Le 15/03/2017 à 16:59, David Ahern a écrit :
> >> >>>> On 3/15/17 9:57 AM, Amine Kherbouche wrote:
> >> >>>>>     > 1) More than 2 labels in the kernel at a time, when will this
> >> be
> >> >>>>>     > allowed in the kernel?
> >> >>>>>     >
> >> >>>>>
> >> >>>>> I don't understand why iproute2 and kernel are not sync when it
> >> comes to
> >> >>>>> the max stacked labels, iproute2 should export kernel headers.
> >> >>>>>
> >> >>>> https://marc.info/?l=linux-netdev&m=146913202123729&w=2 <https://marc.info/?l=linux-netdev&m=146913202123729&w=2>
> >> >>>>
> >> >
> >>
> >
> >
> >
> > -- 
> > Amine
> >
> >
> >
> > ----------
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> > frr mailing list
> > frr at lists.nox.tf
> > https://lists.nox.tf/listinfo/frr <https://lists.nox.tf/listinfo/frr>

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