Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

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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:
• 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.
Figure 61 on page 273 shows a point-to-multipoint LSP with multiple egress LSRs. The
multicast source sends a packet to the ingress router, LSR 1, which in turn sends the
packet on the point-to-multipoint LSP to the branch router, LSR 2. The branch router,
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JunosE 11.2.x BGP and MPLS Configuration Guide