Distribution Protocol (MLDP)-supported multicast VPN (MVPN) allows VPN
multicast streams to be aggregated over a VPN-specific tree. No customer state
is created in the MLDP core;, there is only state for default and data
multicast distribution trees (MDTs). In certain scenarios, the state created
for VPN streams is limited and does not appear to be a risk or limiting factor.
In these scenarios, MLDP can build in-band MDTs that are transit Label Switched
Trees used in a VPN
space are MDTs. Trees used in the global table are transit point-to-multipoint
(P2MP) or multipoint-to-multipoint (MP2MP) LSPs. In both cases, a single
multicast stream (VPN or not) is associated with a single LSP in the MPLS core.
The stream information is encoded in the Forwarding Equivalence Class (FEC) of
the LSP. This is in-band signaling.
signaling uses access control lists (ACLs) with the range of the multicast (S,
G) to be transported by the MLDP LSP. Each multicast channel (S, G) maps,
one-to-one, to each tree in the in-band tree. The (S,G) join is registered in
the Multicast Routing Information Base (MRIB), which is a client of MLDP. Each
MLDP LSP is identified by the FEC of [(S,G) + RD], where RD is the Route
Distinquisher (RD) obtained from BGP. This differs from MLDP-based MVPN, where
the identity is in a FEC of [MDT #, VPN ID, Tree #]).
The ingress Provider
Edge (PE) device uses the FEC to decode the stream information and associate
the multicast stream with the LSP (in the FEC). This service model is only
applicable for transporting Protocol Independent Multicast (PIM)
source-specific multicast (SSM) traffic. There is no need to run PIM over the
LSP because the stream signaling is done in-band.
The MLDP In-Band
Signaling/Transit Mode feature is supported on IPv4
in-band signaling and MLDP-based MVPN cannot be supported in the same VRF.