Ps For An Mpls Te Tunnel; Protocols And Standards - H3C S5500-HI Series Mpls Configuration Manual

PS for an MPLS TE tunnel

Protection switching (PS) refers to establishing one or more protection tunnels (backup tunnels) for a
primary tunnel. A primary tunnel and its protection tunnels form a protection group. When the primary
tunnel fails, data is switched to a protection tunnel immediately, greatly improving the reliability of the
network. When the primary tunnel recovers, data can be switched back to the primary tunnel.
Protection switching mode
The device supports only 1:1 protection switching, where one protection tunnel is used to service one
primary tunnel. Two tunnels exist between the ingress and egress, one primary and one backup.
Normally, user data travels along the primary tunnel. If the ingress finds a defect of the primary tunnel by
using a probing mechanism, it switches data to the protection tunnel.
Protection switching triggering mode
Protection switching may be command triggered or signal triggered.
Command switching refers to a PS triggered by an externally configured switching command,
1.
which can define the following switching actions:
clear—Clears all configured switching actions.
lock (lockout of protection)—Always uses the primary LSP to transfer data.
force (forced switch)—Forces data to travel on the backup LSP.
manual (manual switch)—Switches data from the primary LSP to the backup LSP or vice versa.
Signal switching (Signal Fail) refers to a PS automatically triggered by a signal fail declaration. For
2.
example, a PS occurs when BFD detects that an MPLS TE tunnel fails.
The following shows the externally configured switching actions and the signal fail switching, in
descending order of priority:
Clear
Lockout of protection
Forced switch
Signal fail
Manual switch
In practice, a switching command takes effect only when its priority is higher than that of a signal fail
declaration. When you have configured a switching action on your switch, to change the action to the
one that has a lower priority, you must first configure the clear action and then configure the new
switching action.
Path switching mode
The primary and backup tunnels in a protection group support unidirectional path switching mode. In this
mode, only the ingress node performs path switching, and the ingress node does not notify the egress
node to perform path switching.

Protocols and standards

• RFC 2702, Requirements for Traffic Engineering Over MPLS
RFC 3212, Constraint-Based LSP Setup using LDP
•
RFC 2205, Resource ReSerVation Protocol
•
RFC 3209, RSVP-TE: Extensions to RSVP for LSP Tunnels
•
101