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Re: Label Set Object
John Drake wrote:
> Is it the case that ALL current SONET/SDH equipment has the restriction that
> the labels (timeslots) must be the same in both directions?
Nobody can answer this question, while none of us has a complete overview of
equipment in the field and under design :-).
SDH/SONET (and OTN) networks are networks optimised for bi-directional
connectivity. Uni-directional connections are supported as kind of "exception"
on the generic bidirectional rule. SDH standards are assuming bidirectional
Sometimes a unidirectional connection causes the set up of a bidirectional
connection of which only one direction is used (and alarming in the other
direction is disabled).
People are asking questions with respect to unidirectional connection support in
SDH standards. The use of functional modelling method supports so far the
specific unidirectional connection issues (e.g. no RDI/REI return) raised; but
it is only at this point where you can show how a unidir connection would/should
> If this is the
> case, then it's really simple; for an SONET/SDH LSP, only the upstream label
> needs to be specified, and the downstream label MUST be the same.
> One the other hand, if not all current SONET/SDH equipment has this
> restriction or the current SONET/SDH standards allow the labels (timeslots)
SDH/SONET networks are build with the requirement that the timeslots in the two
directions are the same. (Note - same requirement applies to ATM networks in
which VPI/VCI for the two directions must be the same).
> to be different in each direction, then label set with one value or explicit
> label control would be useful for equipment that does have this restriction.
> -----Original Message-----
> From: Suresh Katukam [mailto:email@example.com]
> Sent: Wednesday, May 08, 2002 3:23 PM
> To: Zafar Ali
> Cc: Manoj Agiwal; Manoj Agiwal; 'Ccamp (E-mail); mpls@UU. NET (E-mail)
> Subject: RE: Label Set Object
> For TDM, since you have to use same labels in both directions, why do you
> have to specify anything at all?
> How can a downstream TDM node pick a label that does not match with
> Upstream label for
> a bidirectional LSP? If it picks any other label, LSP is not functional.
> If there are Uni-directional LSPs in TDM and if you have different types of
> time slots available
> in both directions, then one may be able to setup bidirectional LSP on
> different links or
> different labels. This is in theory and not in practice.
> So in practice, one does not need to specify LABEL SET or Suggested label
> for TDM links.
> At 01:53 AM 5/8/2002 -0400, Zafar Ali wrote:
> >At 11:11 AM 5/8/2002 +0530, Manoj Agiwal wrote:
> >>Hi ,
> >> I guess in that case we can use Suggested Label , Label Set still can
> >> still be avoided .
> >Hi Manoj,
> >No, the use of suggested label in this case would NOT be correct, as the
> >suggested labels can be ignored/ overridden by the receiving node.
> >Regards... Zafar
> >>Regards ,
> >>-----Original Message-----
> >>From: Zafar Ali [mailto:firstname.lastname@example.org]
> >>Sent: Wednesday, May 08, 2002 11:05 AM
> >>To: Manoj Agiwal; 'Ccamp (E-mail)
> >>Cc: mpls@UU. NET (E-mail)
> >>Subject: Re: Label Set Object
> >>At 10:00 AM 5/8/2002 +0530, Manoj Agiwal wrote:
> >>>Hi ,
> >>> In gmpls signaling extensionsions for RSVP-TE , ccamp
> >>> architecture on
> >>>gmpls has described Label Set object usage
> >>> only for the "optical" domain viz. for carrying wavelengths (
> >>>9.9 draft-ietf-ccamp-gmpls-architecture-02.txt) .
> >>> Do we require to send Label set(i.e. time slots) for TDM
> >>> switching as
> >>>well . In what way it can be useful .
> >>Dear Manoj,
> >>Yes, label set object is also useful in TDM case. E.g., SONET poses an
> >>additional requirement that the two interfaces of a bidirectional LSP
> >>SHOULD traverse the exact same link with the same SUKLM values for the
> >>two directions.
> >> The label set object can be used to constrain the downstream label to
> >> the same as the upstream label.
> >>Regards... Zafar
> >>>Regards ,
> >>Zafar Ali
> >>Cisco Systems
> >>(734) 276-2459
> >>100 S Main St. #200
> >>Ann Arbor, MI 48104.
> >>email: email@example.com
> >Zafar Ali
> >Cisco Systems
> >(734) 276-2459
> >100 S Main St. #200
> >Ann Arbor, MI 48104.
> >email: firstname.lastname@example.org
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