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Overview
An RSVP LSP tunnel adds the concept of a forwarding
adjacency, similar to the one used for generalized Multiprotocol Label
Switching (GMPLS). (For more information about GMPLS, see GMPLS.)
The forwarding adjacency creates a tunneled path
for sending data between peer devices in an RSVP LSP network. Once
a forwarding adjacency LSP (FA-LSP) has been established, other LSPs
can be sent over the FA-LSP by using Constrained Shortest Path First
(CSPF), Link Management Protocol (LMP), Open Shortest Path First (OSPF),
and RSVP.
To enable an RSVP LSP tunnel, the JUNOS software
uses the following mechanisms:
- LMP—Originally designed for GMPLS, LMP establishes
forwarding adjacencies between RSVP LSP tunnel peers, and maintains
and allocates resources for traffic engineering links (TE links).
- OSPF extensions—OSPF was designed to route packets
to physical and logical interfaces related to a Physical Interface
Card (PIC). This protocol has been extended to route packets to virtual
peer interfaces defined in an LMP configuration.
- RSVP-TE extensions—RSVP-TE was designed to signal
the setup of packet LSPs to physical interfaces. The protocol has
been extended to request path setup for packet LSPs travelling to
virtual peer interfaces defined in an LMP configuration.
The following limitations exist for LSP hierarchies:
- Circuit cross-connect (CCC)-based LSPs are not supported.
- Graceful restart is not supported.
- Link protection is not available for FA-LSPs or at the
egress point of the forwarding adjacency.
- Point-to-multipoint LSPs are not supported across FA-LSPs.
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