LDP has also been extended to create point-to-multipoint and multipoint -to-multipoint
LSPs (as mLDP). The point-to-multipoint LSPs created are analogous to the trees created
by PIM-SSM in IP multicast, and the multipoint-to-multipoint LSPs to trees created by
bidirectional PIM. mLDP may be used to carry IP multicast over MPLS or in multicast
VPLS (see section on IP multicast in VPLS below).
RSVP-TE Signalling As mentioned previously, RSVP-TE (documented in RFC 3209)
creates point-to-point LSPs. RSVP-TE is an extension of the RSVP protocol (documented
in RFC 2205), which was designed to create bandwidth reservations across IP
networks. An RSVP-TE LSP is established using the following steps:
?– The ingress LSR computes a path to the egress LSR. In general, this path is computed
using a Constrained Shortest Path First algorithm (CSPF) that takes as
inputs the LSP destination, the bandwidth, and QoS requirements for the LSP,
any explicit user-supplied constraints (for example, links or nodes to include or
exclude from the path), and the Traffic Engineering Database (TED). The TED is
an enhanced version of the IGP link state database that includes information on
available bandwidth, link affinities (such as which links are suitable for different
traffic types), and traffic engineering metrics, which can be used as an alternative
to the IGP metric.
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