Subject: question: draft-many-optical-restoration

From: Akshay Adhikari <[email-masked]>
Date: Sat, 17 Nov 2001 20:08:50 -0500

Hello, 

I have a a few questions about draft-many-optical-restoration. 

1. The draft says that when a unidirectional failure is detected, a
notification message is sent from the source of the failure to the
ingress and egress nodes. 

If the provisioned strategy is used, the ingress only has to reconfigure
its OXC to use a different outgoing interface (theoutgoing interface for
the backup lightpath) instead of the current one (the outgoing interface
for the primary path). 
Similarly, the egress also has to configure its outgoing interface upon
receiving the failure notification message. 

Why does the egress have to configure its outgoing interface? I am not
very familiar with GMPLS, but I think this is because of the assumption
that lightpaths are bidirectional. 

Is this correct? 

2. Is it correct that for the provisioned case, the rest of of the OXCs
along the backup path (except the ingress) are already configured (while
setting up the primary lightpath), so that a lightpath create message is
not required to establish the backup path upon failure? 

3. Therefore, if we consider unidirectional lightpaths in the
provisioned case, then the ingress does not need to inform the egress
that it has swithced to the backup path, (which it does currently by a
notification message sent to the egress after it has reconfigured its
outgoing interface). 

Thus, the signaling that is needed is only

a). Node which detects failure sends failure notification to ingress and
egress of each failed lightpath. 

b). Upon receiving the failure notification, the ingress simply
reconfigures itself to send data out the backup lightpath. 

There wont be a need for the ingress to send a notification to the
egress, and vice versa. 

Is this correct? 

TIA,
akshay