[frr] 2 MPLS Questions

David Ahern dsa at cumulusnetworks.com
Thu Apr 6 09:36:06 EDT 2017


net-next tree has the patch set increasing number of labels. Allows up
to 30 labels for ingress (ip->mpls) and routing (mpls->mpls).

An mpls_route is limited to 4096 bytes (number of nexthops + labels); an
lwt (ingress) route is under 128 bytes. With the latest set users of
N-labels takes the performance hit of each additional label.


On 3/23/17 1:34 PM, Amine Kherbouche wrote:
> Olivier,
> 
>     The best for me, is to have the possibility to recompile the MPLS
>     kernel module with the new value the MAX_LABEL_STACK and then let
>     our Segment Routing implementation read this value to determine
>     what's feasible.
> 
> Yes but we still need a default value.
> You have also to see the perf impact, now the current mpls entry size in
> linux kernel is under
> a cache line, even using 12 stacked labels, we are always under a cache
> line but beyond
> this value we're going to see performance issue.
> 



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