Re: GRSVP-TE and MSSPRING

["Diego Caviglia" <Diego.Caviglia@marconi.com>]

Hi Adrian,
          some doubts about the solution you suggested arises in my mind.

Suppose we are in the following scenario.

                                     |                   MSSPRING
|
TNE1<------>TNE2<------>TNE3<------>TNE4<------>TNE5<------>TNE6<------>TNE7<------>TNE8
                                            1          1            1
x
                                            2          2            2
 2

TNEs 4, 5, 6, 7 and 8 are part of a MSSPRING.
Number below the Link indicates the Label availability an x indicates that
the Label is not available.

Up to TNE 4 the signallin procedures as usual then TNE4 has to select the
UPSTREAM LABEL and it choose Label1.

Label1 is good up to TNE 7 that refuses it (it refuses the Label1 because
it knows that is part of a MSSPRING and thus cannot change the Label,
otherwise for "normal" -"normal" menas no MSSPRING- signalling an UPSTREAM
LABEL with value 1 is good for TNE7) and issues a PathErr with
AcceptableLabelSet that indicates Label2.

Now my concern is about who process the PathErr with the
AcceptableLabelSet.  Is TNE6 is TNE1 or is TNE4?

As far as I've understood is TNE 6.

TNE6 removes the XC, if it created it, and propagates the PathErr Upstream.

The Upstream propagation of the PathErr with the AccetableLabelSet is
fundamental for the procedure.

TNE5 behave as TNE6.  TNE4 now have the right information and can send out
a Path Message with Label2.  Is my interpretation correct?

If yes it seems a sort of crankback.

Regards.

Diego




"Adrian Farrel" <adrian@olddog.co.uk> on 25/11/2003 22.44.33

Please respond to "Adrian Farrel" <adrian@olddog.co.uk>

To:    <ccamp@ops.ietf.org>, "Diego Caviglia" <Diego.Caviglia@marconi.com>
cc:

Subject:    Re: GRSVP-TE and MSSPRING


Diego,

I believe that if you use Label Set and Acceptable Label Set you will
arrive at the right
result.
It may take a few messages backwards and forwards to sort it out.

Regards,
Adrian
----- Original Message -----
From: "Diego Caviglia" <Diego.Caviglia@marconi.com>
To: <ccamp@ops.ietf.org>
Sent: Tuesday, November 25, 2003 3:00 PM
Subject: GRSVP-TE and MSSPRING


> Hi all,
>               MSSPRING has been defined in ITU-T G.841 and is widely used
> as inherent protection scheme in transport network (SDH).
>
> MSSPRING introduces some constraints to Label selection due to the
> impossibility to change TimeSlot (a.k.a. Label) inside a MSSPRING ring.
>
> In case of bi-directional LSP Upstream TNE has to choose the Label and
> signal it by means of the UPSTREAM Label obj but if the TNE is inside a
> MSSPRING ring it MUST choose a Label that is free on all the TNE
traversed
> by the LSP that are part of the MSSPRING ring.
>
> Of course the problem is that it does not have that information.
>
> My question is how can I signal, with GRSVP-TE, a bidirectional LSP that
> traverses an MSSPRING ring?
>
> My impression is that I can not.
>
> Any answer is welcome.
>
> Regards
>
> Diego
>
>
>
> ------------------------------------------
> Diego Caviglia
> Marconi - Optical Networks
> ASTN/GMPLS - System Design Manager
> Via A. Negrone 1/A
> 16153 Genoa - Italy
> Phone: +390106003736
>
>
>
>
>
>