Subject: [TICTOC] Bidirectional LSPs for timing packets

From: "Bhatia, Manav (Manav)" <[email-masked]>
Date: Wed, 2 Feb 2011 08:27:50 +0530

Hi,

We had some discussion about using bidirectional LSPs for 1588 (and possibly NTP as well) in our mailing list. The reason we discussed this was to ensure that the forward and the reverse paths are same for the timing packets as an asymmetrical path will adversely affect the timing operation.

This becomes a challenge with MPLS as LSPs are unidirectional. The bidirectional LSPs are guaranteed only in GMPLS and they will be symmetric. The standard MPLS has no such thing. LSPs in each direction can use different paths. We would need to define some mechanism to set up symmetrical LSP paths for regular MPLS as well. We could technically use RROs to trace back the path but that can fail the TE requirements in the reverse direction. Also the paths cannot be guaranteed when doing FRR in case of failures.

Cheers, Manav

--
Manav Bhatia,
IP Division, Alcatel-Lucent,
Bangalore - India