Figure 6-2
Exchange of LDP-PW packets
Loopback1
1.1.1.1/32
Loopback1
2.2.2.2/32
PE1
PE2
mpls l2vc 2.2.2.2 101
mpls l2vc 1.1.1.1 101
Request
parameter match , VC up
Mapping
Mappi
ng
parameter match , VC up
Notification
AC/Tunnel state changed
AC/Tunnel state changed
The dynamic allocation of LDP-PW labels is performed in the receiving and sending directions.
On the basis of Martini, the dynamic PW adds the optional status parameter in the Mapping
packet and supports the Notification packet.
When the network is in the unstable state, the Notification packet can decrease the number of
packet exchanges.
For example, if an AC on a PE flaps, the Notification packet is sent to notify the AC status. After
receiving the packet, the peer does not dismantle the VC.
However, in the Martini mode, the Withdraw packet is sent repeatedly. Thus, the PW is set up
and dismantled repeatedly.
NOTE
PWE3 supports Notification mode to negotiate PW state information. The Withdraw packet is compatible
with withdraw labels in PWE3. The negotiation of two ends of the PW determines the mode to be used.
The process of tearing down a dynamic PW is described as follows:
shows the packet exchange during the process of tearing down a dynamic PW.
Quidway S7700 Smart Routing Switch
Configuration Guide - VPN
6 PWE3 Configuration
Issue 01 (2011-07-15)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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