Ldp Graceful Restart Overview; Figure 58: Ldp Tunneled Through An Rsvp-Te Core - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - BGP AND MPLS CONFIGURATION GUIDE 2010-10-12 Configuration Manual

JunosE 11.3.x BGP and MPLS Configuration Guide
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LDP Graceful Restart Overview

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Figure 58: LDP Tunneled Through an RSVP-TE Core

In the network topology illustrated in Figure 58 on page 256, the RSVP-TE LSP consists
of LSR 2, LSR 3, LSR 4, and LSR 5. The LDP LSP consists of LER 1, LSR 2, LSR 5, and LER
6. The RSVP-TE tunnel appears to LDP as a single hop.
The initial LDP label 19 is switched with label 24 at LSR 2. Because this is the entrance
to the RSVP-TE tunnel, label 21 is pushed onto the stack. Label 21 is switched with label
43 at LSR 3. Label 43 is switched with label 56 at LSR 4. LSR 5 pops both labels, pushes
label 17, and forwards the packet to LER 6.
On the LDP routers that are on the edge of the core, you must configure a list of peer
addresses. The LDP router sends targeted hello messages to those addresses in order
to establish targeted sessions across the RSVP-TE domain. The list includes other LDP
routers on the edge of the core; for example, in Figure 58 on page 256, you include the
address of LSR 5 in the list configured on LSR 2.
MPLS Label Distribution Methodology on page 227
MPLS Label Switching and Packet Forwarding Overview on page 218
MPLS Label Distribution Protocols Overview on page 238
IP Data Packet Mapping onto MPLS LSPs Overview on page 229
The graceful restart mechanism minimizes the negative effect on MPLS forwarding across
an LSR restart. You can configure the neighbors of the LSR to wait for the LSR to restart
(helper mode). When the LSR restarts, the neighbors mark their current label mapping
entries from the LSR as stale. If the LSR recovers within the proper interval, the entries
are no longer marked as stale and are used as they were before the LDP connection
failed. If the LSR does not recover in time, the entries are deleted.
LDP graceful restart supports only the downstream-unsolicited mode of label distribution.
Successful operation of LDP graceful restart requires that stateful SRP switchover (high
availability) be configured on the router. Although you can configure LDP graceful restart
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