MPLS Guide Label Distribution Protocol
3HE 18686 AAAB TQZZA © 2022 Nokia.
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Communication within LDP tasks is typically done by interprocess communication
through the event queue, as well as through updates to the various data structures.
The following list describes the primary data structures that LDP maintains:
• FEC/label database — this database contains all the FEC-to-label mappings,
including both sent and received. It also contains both address FECs (prefixes
and host addresses) as well as service FECs (L2 VLLs).
• Timer database — this database contains all the timers for maintaining sessions
and adjacencies
• Session database — this database contains all the session and adjacency
records, and serves as a repository for the LDP MIB objects
5.1.3 LDP Subsystem Interrelationships
Figure 22 shows the relationships between LDP subsystems and other 7705 SAR
subsystems. The following sections describe how the subsystems work to provide
services.
5.1.3.1 Memory Manager and LDP
LDP does not use any memory until it is instantiated. It preallocates some amount of
fixed memory so that initial startup actions can be performed. Memory allocation for
LDP comes out of a pool reserved for LDP that can grow dynamically as needed.
Fragmentation is minimized by allocating memory in large chunks and managing the
memory internally to LDP. When LDP is shut down, it releases all memory allocated
to it.
5.1.3.2 Label Manager
LDP assumes that the label manager is up and running. LDP will abort initialization
if the label manager is not running. The label manager is initialized at system
boot-up; hence anything that causes it to fail will likely indicate that the system is not
functional. The 7705 SAR uses a label range from 28 672 (28K) to 131 071
(128K-1) to allocate all dynamic labels, including VC labels.
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