Ldp Nsr; Ldp-Igp Synchronization - HP FlexNetwork 10500 Series Configuration Manual

6. When the MPLS Forwarding State Holding timer expires, the GR restarter deletes all stale
MPLS forwarding entries.
7. When the LDP Recovery timer expires, the GR helper deletes all stale FEC-label mappings.
Figure 13 LDP GR operation
GR restarter
Protocol
restarts
MPLS
forwarding state
holding time

LDP NSR

To use LDP nonstop routing (NSR), the device must have a minimum of two MPUs.
LDP NSR ensures nonstop services of LDP when LDP has redundant processes on multiple MPUs.
In contrast to Graceful Restart, NSR does not require an LDP peer to recover MPLS forwarding
information.
LDP NSR backs up protocol states and data (including LDP session and LSP information) from the
active process to the standby process. When the LDP active process fails, the standby process
becomes active and takes over processing seamlessly. The LDP peers are not notified of the LDP
interruption. The LDP session stays in Operational state, and the forwarding is not interrupted.
The LDP active process fails when one of the following situations occurs:
•
The active process restarts.
•
The MPU where the active process resides fails.
•
The MPU where the active process resides performs an ISSU.
•
The LDP process' position determined by the process placement feature is different from the
position where the LDP process is operating.

LDP-IGP synchronization

Basic operating mechanism
LDP establishes LSPs based on the IGP optimal route. If LDP is not synchronized with IGP, MPLS
traffic forwarding might be interrupted.
LDP is not synchronized with IGP when one of the following situations occurs:
•
A link is up, and IGP advertises and uses this link. However, LDP LSPs on this link have not
been established.
•
An LDP session on a link is down, and LDP LSPs on the link have been removed. However, IGP
still uses this link.
•
The Ordered label distribution control mode is used. IGP used the link before the local device
received the label mappings from the downstream LSR to establish LDP LSPs.
Set up an LDP session, and identify that
they are LDP GR capable
Re-establish the LDP session
Send label mappings
GR helper
Reconnect time
LDP recovery time
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