Head End Router

This is the origination point of the LSP. The head end router informs if one to one or facility is desired in the path message session attribute object. After each router along the lsp path receives the path message it acts as a PLR and tries to set up the detour, each PLR informs the HE router if the detour is available or not.

PLR informs the HE router of a failure in 2 ways:-

1> It sends the RESV message to the HE router where the local protection in use flag is set.

2> PathErr message with an ERROR object. The error0x19) — RSVP Notify Error. The error value is0x03) — tunnel locally repaired.

The PLR sends a

code is 25 (

3 (

Once a path error is receivd by the HE router it switches the traffic to a secondary standby LSP, if a standby LSP is not available it tries to initiate a LSP in an Make Before Break (MBB) manner.

When the HE router comes to know that a FRR is in use it starts the MBB process immediately however it initiates the process of establishing the LSP after some time ie after the retry timer expires.

After the MBB process is successful traffic is switched immediately to the standby LSP.