Re: [mpls] Comments on draft-jjb-mpls-rsvp-te-hsmp-lsp

[Manav Bhatia <[e-mail]>]

Hi Eric,

Yes i am the co-author of draft-ietf-tictoc-1588overmpls. I believe we
can use the HSMP LSP described in this draft for timing distribution
irrespective of whether we accept the solution described in the tictoc
draft or not.

[clipped]

> "This is possible because of the link delay calculation performed locally by each node,
> which enables it to calculate the propagation delay over the path.  This scenario
> permits that the same PTP Sync messages would be sent by the PTP master to all the PTP slaves"
>
> implies that each hop in an LSP used for timing distribution would need to examine the packet, modify it,
> and send it on.  Strictly speaking this is outside the scope of this draft, but it seems a heck of
> a thing to just assume, since it is an important prerequisite for this particular use case.

Well, this is precisely what happens when you try to ship timing
packets over MPLS. Each LSR updates the residence time in the 1588
packet before forwarding it downstream.

The following blog post describes the HSMP LSP in detail and should
address most of your questions:
http://routingfreak.wordpress.com/2011/02/27/hub-and-spoke-multi-point-lsps-for-scalable-vpls-architecture/

Cheers, Manav