P2Mp Lsp Data Plane; Procedures At Ingress Ler Node - Alcatel-Lucent 7450 Manual

P2MP LSP Data Plane

A router can act as a leaf for the P2MP LSP tree initiated from the head-end router co-located with
the video source. The router can also act as a branch node serving other leaf nodes and supports
the replication of multicast packets over P2MP LSPs.
P2MP LSP Data Plane
A P2MP LSP is a unidirectional label switched path (LSP) which inserts packets at the root
(ingress LER) and forwards the exact same replication of the packet to one or more leaf nodes
(egress LER). The packet can be replicated at the root of P2MP LSP tree and/or at a transit LSR
which acts as a branch node for the P2MP LSP tree.
Note that the data link layer code-point, for example Ethertype when Ethernet is the network port,
continues to use the unicast codepoint defined in RFC 3032, MPLS Label Stack Encoding, and
which is used on P2P LSP. This change is specified in draft-ietf-mpls-multicast-encaps, MPLS
Multicast Encapsulations.
When a router sends a packet over a P2MP LSP which egresses on an Ethernet-based network
interface, the Ethernet frame uses a MAC unicast destination address when sending the packet
over the primary P2MP LSP instance or over a P2P bypass LSP). Note that a MAC multicast
destination address is also allowed in the draft-ietf-mpls-multicast-encaps. Thus, at the ingress
network interface on an Ethernet port, the router can accept both types of Ethernet destination
addresses.

Procedures at Ingress LER Node

The following procedures occur at the root of the P2MP LSP (head-end or ingress LER node):
1. First, the P2MP LSP state is established via the control plane. Each leaf of the P2MP LSP
5. The user maps a specific multicast destination group address to the P2MP LSP in the base
router instance by configuring a static multicast group under a tunnel interface representing
the P2MP LSP.
6. An FTN entry is programmed at the ingress of the head-end node that maps the FEC of a
received user IP multicast packet to a list of outgoing interfaces (OIF) and corresponding
NHLFEs.
7. The head-end node replicates the received IP multicast packet to each NHLFE. Replication is
performed at ingress toward the fabric and/or at egress forwarding engine depending on the
location of the OIF.
8. At ingress, the head-end node performs a PUSH operation on each of the replicated packets.
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will have a next-hop label forwarding entry (NHLFE) configured in the forwarding plane
for each outgoing interface.
7450 ESS MPLS Guide