Инструкции По Установке для 3com S7906E

 

1-12 

z

 

Advertisement message: Used to create, alter, or remove label bindings. 

z

 

Notification message: Used to provide advisory information and to notify errors. 

For reliable transport of LDP messages, TCP is used for LDP session messages, advertisement 
messages, and notification messages, while UDP is used only for discovery messages. 

A scope of labels that can be assigned to LDP peers is called a label space. A label space can be per 
interface or per platform. A per interface label space is interface-specific, while a per platform label 
space is for an entire LSR. 

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 that the label 
space is per interface, a label space ID of 0 means that the label space is per platform. 

 

Currently, only per platform label space is supported. 

 

 illustrates how LDP distributes labels. 

Label distribution 

LER

LSR A

LSR B

LSR D

LSR C

LSR E

LSR F

LSR G

LSR H

Ingress

Egress

Label request

LSP1
LSP2

Label mapping

 

 

In 

, B is the upstream LSR of C along LSP 1. 

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 in each of the two modes. 

In DoD mode, an upstream LSR sends a label request message containing the description of a FEC to 
its downstream LSR. After receiving the message, the downstream LSR assigns a label to the FEC, 
encapsulates the binding information in a label mapping message and sends the message to the