Devil's Advocate - Segment Routing, Why?

Mark Tinka mark.tinka at seacom.mu
Sun Jun 21 20:00:42 UTC 2020


On 21/Jun/20 19:34, Robert Raszuk wrote:
>
> That is true for P routers ... not so much for PEs. 
>
> Please observe that label space in each PE router is divided for IGP
> and BGP as well as other label hungy services ... there are many
> consumers of local label block. 
>
> So it is always the case that LFIB table (max 2^20 entries - 1M) on
> PEs is much larger then LFIB on P nodes.

I should point out that all of my input here is based on simple MPLS
forwarding of IP traffic in the global table. In this scenario, labels
are only assigned to BGP next-hops, which is typically an IGP Loopback
address.

Labels don't get assigned to BGP routes in a global table. There is no
use for that.

Of course, as this is needed in VRF's and other BGP-based VPN services,
the extra premium customers pay for that priviledge may be considered
warranted :-).

Mark.


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