Point-To-Multipoint Label Switch Path; Path Option For Point-To-Multipoint Rsvp-Te - Cisco ASR 9000 Series Configuration Manual

Implementing MPLS Traffic Engineering
of LSP traffic along an alternative backup path around a network failure, until the TE tunnel source signals a
new end-to-end LSP.
The Point-of-Local Repair (PLR) is a node that selects a backup tunnel and switches the LSP traffic onto the
backup tunnel in case a failure is detected. The receiver of the backup tunnel is referred to as the Merge Point
(MP).
Both Point-to-Point (P2P) and P2MP-TE support only the Facility FRR method from RFC 4090.
Fast reroutable LSPs can coexist with fast reroutable P2P LSPs in a network. Node, link, and bandwidth
protection for P2P LSPs are supported. Both MPLS-TE link and node protection rely on the fact that labels
for all primary LSPs and subLSPs are using the MPLS global label allocation. For example, one single (global)
label space is used for all MPLS-TE enabled physical interfaces on a given MPLS node.
Related Topics
Point-to-Multipoint Traffic-Engineering Overview, on page 140
Point-to-Multipoint RSVP-TE , on page 142

Point-to-Multipoint Label Switch Path

The Point-to-Multipoint Label Switch Path (P2MP LSP) has only a single root, which is the Ingress Label
Switch Router (LSR). The P2MP LSP is created based on a receiver that is connected to the Egress LSR. The
Egress LSR initiates the creation of the tree (for example, tunnel grafting or pruning is done by performing
an individual sub-LSP operation) by creating the Forwarding Equivalency Class (FEC) and Opaque Value.
Grafting and pruning operate on a per destination basis.
Note
The Opaque Value contains the stream information that uniquely identifies the tree to the root. To receive
label switched multicast packets, the Egress Provider Edge (PE) indicates to the upstream router (the next
hop closest to the root) which label it uses for the multicast source by applying the label mapping message.
The upstream router does not need to have any knowledge of the source; it needs only the received FEC to
identify the correct P2MP LSP. If the upstream router does not have any FEC state, it creates it and installs
the assigned downstream outgoing label into the label forwarding table. If the upstream router is not the root
of the tree, it must forward the label mapping message to the next hop upstream. This process is repeated
hop-by-hop until the root is reached.
By using downstream allocation, the router that wants to receive the multicast traffic assigns the label for it.
The label request, which is sent to the upstream router, is similar to an unsolicited label mapping (that is, the
upstream does not request it). The upstream router that receives that label mapping uses the specific label to
send multicast packets downstream to the receiver. The advantage is that the router, which allocates the labels,
does not get into a situation where it has the same label for two different multicast sources. This is because it
manages its own label space allocation locally.

Path Option for Point-to-Multipoint RSVP-TE

P2MP tunnels are signaled by using the dynamic and explicit path-options in an IGP intra area. InterArea and
InterAS cases for P2MP tunnels are signaled by the verbatim path option.
Path options for P2MP tunnels are individually configured for each sub-LSP. Only one path option per sub-LSP
(destination) is allowed. You can choose whether the corresponding sub-LSP is dynamically or explicitly
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