Subject: Observations OSPF RSVP...

From: "[email-masked]" <[email-masked]>
Date: Thu, 13 Mar 2003 16:45:58 +0100

Hi all,

i see at least two advantages in using Opaque LSA insted of PathErr (quite the same for the Notifies ) in this scenario: precalculated and presignalled backup disjoint paths for protected LSPs in MPLS Network, availability of fast detection mechanism ( from lower levels ) of link failure.

1) Since Opaque LSAs don' t trigger an SPF calculation in the routers they cross, all the Network is soon informed about the link failure event and IN PARALLEL each router can do the label switching on the backup LSPs ( after having controlled the presence of protected LSPs starting from it and interested by the link failure ). 

2) Since i refer to protected LPSs ( they are relatively few ), thinking in a scenario in which there should be a return to the first active LSP when the link failed returns to be UP ( that is a second switch from backup LSP to the  first active LSP ), could it be not necessary to send the PathTears immediately to cleanup resources? This will bring two beneficts: no PathTears and ResvTear sent immediately in  the Network and no signalling messages storm when the link returns up ( after a not long period ), when it's probable that all the backup LSPs will return on that link (the link that went down). 

Thanks in advance for your kind answers and observations.

Giovanni di Giacomo