[c-nsp] segment routing/evpn on ASR920

[James Bensley]

On 30 January 2019 15:15:02 GMT, Aaron Gould <aaron1 at gvtc.com> wrote:
>I read that SR/SPRING is an alternative to LDP or RSVP... seems that
>SR/SPRING is a label distribution protocol.  Meaning, in my mind, it's
>a way
>to learn labels...mpls labels I guess.  If so, would we refer to EVPN
>as
>EVPN-SR?  If so, would it follow that a non-sr network, one that has
>employed ldp for label learning, with evpn, would be referred to as
>EVPN-LDP
>?  I'm not thinking so.
>
>Further, I recall reading that EVPN is Control Plane, and has a few
>different options for Fwd'ing plane...
>
>EVPN-VXLAN
>EVPN-PBB
>EVPN-MPLS
>...perhaps others...
>
>Tom, I wonder if we/you should look for ASR920 docs/support for
>EVPN-MPLS in
>your desire to see if EVPN will work over SR?
>
>I could be way off.  
>
>-Aaron

Hi Aaron,

SR is allocating and distributing transport labels, not service labels (well, SIDs actually!). For example, with a typical L3 VPN, SR/LDP/RSVP/PCEP distributes the transport labels amongst your PEs and BGP distributes and service labels amongst them.

EVPN uses BGP for signalling too. EVPN can use VXLAN or MPLS for the forwarding plane. This means that when using MPLS for the forwarding plane the EVPN service labels are advertised in BGP, not SR/LDP/RSVP, like an L3 VPN. So someone using "SR+EVPN" means SR for transport labels and BGP for the EVPN labels.

Cheers,
James.