RSVP Control Plane in a P2MP LSP
Page 162 7450 ESS MPLS Guide
RSVP Control Plane in a P2MP LSP
P2MP RSVP LSP is specified in RFC 4875, Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label Switched Paths (LSPs).
A P2MP LSP is modeled as a set of root-to-leaf (S2L) sub-LSPs. The root, for example the head-
end node, triggers signaling using one or multiple path messages. A path message can contain the
signaling information for one or more S2L sub-LSPs. The leaf sub-LSP paths are merged at
branching points.
A P2MP LSP is identified by the combination of <P2MP ID, tunnel ID, extended tunnel ID> part
of the P2MP session object, and <tunnel sender address, LSP ID> fields in the P2MP
sender_template object.
A specific sub-LSP is identified by the <S2L sub-LSP destination address> part of the
S2L_SUB_LSP object and an ERO and secondary ERO (SERO) objects.
The following are characteristics of this feature:
1. Supports the de-aggregated method for signaling the P2MP RSVP LSP. Each root to leaf
is modeled as a P2P LSP in the RSVP control plane. Only data plane merges the paths of
the packets.
2. Each S2L sub-LSP is signaled in a separate path message. Each leaf node responds with
its own resv message. A branch LSR node will forward the path message of each S2L sub-
LSP to the downstream LSR without replicating it. It will also forward the resv message of
each S2L sub-LSP to the upstream LSR without merging it with the resv messages of
other S2L sub-LSPs of the same P2MP LSP. The same is done for subsequent refreshes of
the path and resv states.
3. The node will drop aggregated RSVP messages on the receive side if originated by
another vendor’s implementation.
4. The user configures a P2MP LSP by specifying the optional create-time parameter p2mp-
lsp following the LSP name. Next, the user creates a primary P2MP instance using the
keyword primary-p2mp-instance. Then a path name of each S2L sub-LSP must added to
the P2MP instance using the keyword s2l-path. The paths can be empty paths or can
specify a list of explicit hops. The path name must exist and must have been defined in the
config>router>mpls>path context.
5. The same path name can be re-used by more than one S2L of the primary P2MP instance.
However the to keyword must have a unique argument per S2L as it corresponds to the
address of the egress LER node.
6. The user can configure a secondary instance of the P2MP LSP to backup the primary one.
In this case, the user enters the name of the secondary P2MP LSP instance under the same
LSP name. One or more secondary instances can be created. The trigger for the head-end
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