RFC 9573: MVPN/EVPN Tunnel Aggregation with Common Labels
Recent RFCs 2024-05-24
Summary:
The Multicast VPN (MVPN) specifications allow a single
Point-to-Multipoint (P2MP) tunnel to carry traffic of multiple IP
VPNs (referred to as VPNs in this document). The EVPN specifications
allow a single P2MP tunnel to carry traffic of multiple Broadcast
Domains (BDs). These features require the ingress router of the P2MP
tunnel to allocate an upstream-assigned MPLS label for each VPN or
for each BD. A packet sent on a P2MP tunnel then carries the label
that is mapped to its VPN or BD (in some cases, a distinct
upstream-assigned label is needed for each flow.) Since each ingress
router allocates labels independently, with no coordination among the
ingress routers, the egress routers may need to keep track of a large
number of labels. The number of labels may need to be as large as,
or larger than, the product of the number of ingress routers times
the number of VPNs or BDs. However, the number of labels can be
greatly reduced if the association between a label and a VPN or BD is
made by provisioning, so that all ingress routers assign the same
label to a particular VPN or BD. New procedures are needed in order
to take advantage of such provisioned labels. These new procedures
also apply to Multipoint-to-Multipoint (MP2MP) tunnels. This document
updates RFCs 6514, 7432, and 7582 by specifying the necessary
procedures.