Subject: [Idr] Reply to question on "BGP MPLS-namespaces" from IDR-111 notes

From: Kaliraj Vairavakkalai <[email-masked]>
Date: Wed, 28 Jul 2021 07:14:11 +0000

Hi Swadesh,
Replying to question from IDR-111 notes (https://codimd.ietf.org/notes-ietf-111-idr# )
>4. BGP MPLS-namespaces: Improve Scaling and Convergence in Seamless-MPLS networks [Kaliraj Vairavakkalai] (10 mins)

>https://datatracker.ietf.org/doc/html/draft-kaliraj-bess-bgp-sig-private-mpls-labels/
>Swadesh: How many routes will be seen by the PE if the domain has 100 PEs and 1000 vrfs?
Service-route scale at remote-PE:

Remote PE will see same number of service-routes as before. No difference. RTC may be used to optimally pull only interesting service routes. Nothing new there.

Transport-route scale at remote-PE or remote-BNs:

Remote PE will see reduced number of transport-routes. 1 route per-BN for a CPNH1 representing the region. Instead of 100 PE transport-routes.
                ECMP also order of num-BNs, not order of num-PEs.

MPLS Scale at option-BC local-region BNs:

In above scenario, because there are 100K VRFs in all, and assuming each VRF is doing “per-table label allocation”,

The BN1 will see 100K mpls-routes installed in “<cpnh1>.mpls” table, received via MPLS-Namespace BGP-family from the external-allocator(RR).

The BN takes this load. But frees up all other nodes in the network (BNs, remote-PEs) from consuming resources per Service-Endpoint/PE-lo0.

Assuming the capacity of a BN is 100K mpls routes, and more than 100K VRFs (e.g. PE101 – PE200) get deployed in a region, a new set of BNs can be deployed for “CPNH2”, which serve the next 100K VRFs. Simple scale-out design.

So basically, the “forwarding-resources scale usage” remains confined to the edge of the network, in each region. It uses as much resources as required, very close to the service origination point.

And because that forwarding scale is also function of num-Service-endpoints and not service-routes, PIC or PDC convergence happens quickly in a service-family agnostic manner.

Thanks
Kaliraj

Juniper Business Use Only