Ldp Label Distribution - H3C S9500 Series Operation Manual

Operation Manual – MPLS Basics
H3C S9500 Series Routing Switches
An LDP identifier is used to identify an LSR label space. It is a six-byte numerical value
in the format of <LSR ID>:<Label space ID>, where LSR ID is four-byte long. A label
space ID of 1 means per interface, a label space ID of 0 means per platform.
Note:
Currently, only per platform label space is supported.

1.3.2 LDP Label Distribution

Figure 1-7
Figure 1-7 Label distribution
In Figure
As described previously, there are two label advertisement modes. The main difference
between them is whether the downstream advertises the bindings unsolicitedly or on
demand.
The following details the advertisement process for each of the two modes.
I. DoD mode
In DoD mode, an upstream LSR sends a label request message containing the
description of a FEC to its downstream LSR, which assigns a label to the FEC,
encapsulates the binding information in a label mapping message and sends the
message back to it.
When the downstream LSR responds with label binding information depends on the
label distribution control mode used by the LSR:
In ordered mode, an LSR responds to its upstream LSR with label binding
information only when it receives that of its downstream LSR.
illustrates how LDP distribute labels.
1-7, B is the upstream LSR of C on LSP 1.
Chapter 1 MPLS Basics Configuration
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