Re: RSVP Restart (was Re: update GMPLS signaling documents)

[Yakov Rekhter <yakov@juniper.net>]

Gopal,

[clipped...]

> >>>>If a node supports PSC as well as TDM or LSC interfaces, it
> >>>>might want to advertise different set of parameters in the
> >>>>RESTART_CAP object for data LSPs as opposed to SONET/WDM
> >>>>LSPs which form bearer channels in transport networks.
> >>>>Currently this is not possible.
> >>>>
> >>>>>Can you give us explicit examples as to why and what do
> >>>>>you gain by giving different values for PSC, TDM ?
> >>>>>
> >>>>In case of PSC devices, it may be OK to remove state that
> >>>>is not resynchronized at the end of the recovery period,
>>>>and the recovery period advertised might reflect that.
> >>>>
> >>>>
> >>>>But for LSPs in transport networks, one might want to
> >>>>have a different recovery period to avoid any LSP from
> >>>>going down because of recovery timer expiry.
> >>>>
> >>>There is no requirement for a node to advertise exactly the
> >>>same Restart_Cap on all the interfaces. So, on PSC interfaces
> >>>the node could advertise that it will remove the state that
> >>>isn't syncronized at the end of the recovery period, while
> >>>on the TDM interface precisely the same node could advertise
> >>>that the LSPs would be kept even after the recovery time expires.
> >>>
> >>But to set up LSPs over TDM/LSC interfaces, the PSC interface
> >>is going to be used for signaling - since control and data
> >>planes are decoupled!  So, how will this help?
> >>
> >
> >Help with what ? You asserted that it "is not possible" for
> >"a node that supports PSC as well as TDM and LSC interfaces..
> >to advertise different set of parameters in the RESTART_CAP
> >object for data LSPs as opposed to SONET/WDM LSPs."
> >
> >I pointed out to you that your assertion is incorrect, as
> >there is no requirement for a node to advertise exactly the
> >same Restart_Cap on all of its interfaces.
> >
> I believe your assertion is misleading - If two nodes A and
> B have multiple TDM/LSC links (with out of band signaling)
> between them as well as a PSC link, (they are all unnumbered
> interfaces), there will be only one Hello adjacency between
> A and B, resulting in just one Restart_cap object advertised
> in each direction.
>
> In that case, how can one advertise different values in the
> Restart_cap object for TDM/LSC LSPs as opposed to data LSPs?
> 
> Since there is only one adjacency, the suggestion above to
> treat the node failure as control channel failure does not
> work either, as the restarting node might want to get
> resynchronized for data LSPs.
> 
> I believe your assertion is possible only if all interfaces
> are numbered.  

That is incorrect - what I described is possible if only the
control channel is numbered (note that a control channel, just
like any other link, could have multiple IP addresses assigned to it).

> If so, this is a huge constraint - please
> refer draft-ietf-ipo-carrier-requirements-00, sec 7.4.

In the context of UNI the (multiple) IP addresses assigned
to a control channel could be locally defined. As such
it would meet the requirements of section 7.4 of the draft
you mentioned.

Yakov.