Juniper JUNOSE, Configuration Manual

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Although you can use point-to-point LSPs to provide point-to-multipoint services, this
type of configuration can cause data replication at the ingress LSR or duplicate traffic
within the network. You can use the traffic engineering (TE) capability of LSPs to
achieve consistent QoS control and efficient use of network resources, and create
point-to-multipoint LSPs to deliver data from one ingress LSR to multiple egress LSRs.
The flow of traffic in a point-to-multipoint LSP is not restricted to the paths that are
followed for multicast or shortest path routing; instead, you can explicitly configure
the values to determine the path. Packet replication takes place only when packets
are forwarded to two or more different destinations requiring different network
paths.
A point-to-multipoint TE tunnel is composed of multiple point-to-multipoint LSPs. To
scale to a large number of nodes or branches in a point-to-multipoint LSP, each LSP
is uniquely identified by a point-to-multipoint ID, which is unique for the entire LSP,
regardless of the number of branches or leaves it contains. A point-to-multipoint LSP
is composed of multiple source-to-leaf sub-LSPs. These sub-LSPs are formed between
the ingress and egress LSRs to form the point-to-multipoint LSP.
Point-to-multipoint LSPs can be signaled using one or more path messages. If a path
message signals only one sub-LSP, it targets only one leaf in the point-to-multipoint
tunnel. Because a single path message might not be large enough to contain all the
sub-LSPs in the tunnel and also because you can create path messages specific to a
sub-LSP in the tunnel, you can use multiple path messages. However, if you want to
minimize the number of control messages required to configure a point-to-multipoint
tunnel, you need to use a single path message to signal multiple sub-LSPs.
The following are some of the benefits of using point-to-multipoint LSPs:
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A point-to-multipoint LSP allows you to use MPLS TE for point-to-multipoint data
distribution. This functionality provides better control over the path chosen to
transmit traffic than that provided by IP multicast.
■
You can add and remove branch LSPs from a main point-to-multipoint LSP
without disrupting traffic. The unaffected parts of the point-to-multipoint LSP
continue to function normally.
■
You can enable link protection on a point-to-multipoint LSP. Link protection can
provide a bypass LSP for each of the branch LSPs that make up the
point-to-multipoint LSP. If any of the primary paths fail, traffic can be quickly
switched to the bypass path.
■
You can configure branch LSPs statically, dynamically, or as a combination of
static and dynamic LSPs.
■
You can enable graceful restart on point-to-multipoint LSPs.
Using E Series Routers as Egress LSRs
You can use E Series routers as egress LSRs in a point-to-multipoint LSP. To create
a point-to-multipoint LSP and to use E Series routers as egress LSRs, no special
configuration is required. The configuration that you made for point-to-point LSPs,
which enables MPLS RSVP-TE on the interface that must signal an LSP in that virtual
router context, is sufficient.
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Point-to-Multipoint LSPs Overview
JUNOSe 11.0.x BGP and MPLS Configuration Guide