This section describes how to configure bit-error-triggered pseudo wire (PW) switching.
In a scenario in which a Resource Reservation Protocol-Traffic Engineering (RSVP-TE) tunnel with traffic engineering (TE) hot standby protection carries Layer 2 virtual private network (L2VPN) services and PW redundancy is configured, you can configure bit-error-triggered PW switching in addition to bit-error-triggered RSVP-TE tunnel switching. If the primary and backup constraint-based routed label switched paths (CR-LSPs) of the RSVP-TE tunnel are both in the excessive bit error rate (BER) state or the TE hot standby tunnel fails and bit-error-triggered RSVP-TE tunnel switching cannot protect services against bit errors, bit-error-triggered PW switching can do so.
The principles for bit-error-triggered PW switching are as follows:
If the RSVP-TE tunnel carrying the primary PW enters the excessive BER state but the RSVP-TE tunnel carrying the secondary PW is in the normalized BER state, traffic switches to the secondary PW.
If the RSVP-TE tunnel carrying the primary PW enters the normalized BER state, traffic switches back to the primary PW.
If the RSVP-TE tunnels carrying the primary and secondary PWs are both in the excessive BER state, traffic travels along the primary PW.
The bit error status of the RSVP-TE tunnel carrying the PW refers to the bit error status of the CR-LSP that transmits traffic in the tunnel.
For an SS-PW, bit-error-triggered protection switching is enabled on endpoint provider edges (PEs).
For an MS-PW, bit-error-triggered protection switching is enabled on both endpoint PEs and intermediate superstratum provider edges (SPEs).
Before configuring bit-error-triggered PW switching, complete the following tasks:
Configure PW redundancy.