Protection object in restoration signaling

[Yoshihiko SUEMURA <y_suemura@mwc.biglobe.ne.jp>]

P&R Design Team,

In the 1:1/Shared Mesh Restoration described in
draft-lang-ccamp-gmpls-recovery-e2e-signaling-02, activation of a
secondary LSP is done only by a Path message. The Protection object is
carried only in a Path message.
However, I think a Resv message should also carry the Protection object.

Consider the following case.

   A-----------B
    \         /
     C-------D
    /         \
   E           F

A-B:     Primary LSP
A-C-D-B: Secondary LSP
E-C-D-F: Extra (preemptable) LSP

Activating the Secondary LSP using only a Path message may cause
unintended connection (A-C-D-F) between the Secondary LSP and the Extra
LSP. This can be prevented by applying a two-way activation scheme using
both Path and Resv messages. You can delete the Extra LSP by the Path
message, and activate the Secondary LSP by the Resv message. 
However, if the Resv message for activation does not carry the
Protection object, it cannot be distinguished from a refresh Resv
message. This still causes unintended connection in the following case.

(1) At node C, a crossconnect for the Extra LSP is deleted when
receiving a Path message.
  
(2) Then, if node C receives a refresh Resv message from D, it sets up a
crossconnect for the Secondary LSP because it cannot distinguish the
refresh Resv message from a Resv message for activation.
    
If (2) occurs before D deletes a crossconnect for the Extra LSP, it
causes unintended connection between the Secondary LSP and the Extra LSP.

As a solution for the above problem, I propose to add the Protection
object to a Resv message. The unintended connection can be prevented
because you can distinguish a Resv message for activation from a refresh
Resv message by watching the S bit.


Best regards,

Yoshihiko

-----------------------------------------------------------------
Yoshihiko SUEMURA 

NEC Corporation
E-mail: y-suemura@bp.jp.nec.com