Subject: Re: SE style in optical neyworks

From: gmpls gmpls <[email-masked]>
Date: Sun, 14 Apr 2002 21:55:51 -0700 (PDT)

Hi,

I need some more clarification on this regard.
The OIF UNI v1.0 standard says UNI only supports the
FF style of reservation. Since Optical network which
main purpose is to provide service for UNI clients,
would  have to support same set reservation styles
which UNI needs.

So Is there a need for supporting SE style of
reservation in the optical domain?

Regards

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From: Zhi-Wei Lin <[email-masked]>
Date: Mon, 15 Apr 2002 09:50:14 -0400

Hi,

This implication doesn't necessary apply. What the UNI requests requires 
that the network be able to support. But this doesn't necessarily imply 
that what UNI has translates to what the network must also have and no 
more...

The SE style discussion is orthogonal to this...

Zhi

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From: David Charlap <[email-masked]>
Date: Mon, 15 Apr 2002 10:00:56 -0400

> reservation in the optical domain?

What's the point?

In an optical network, you are signaling wavelengths or time slices. 
How could you conceivably have two time-slices share resources?  Or two
wavelengths?

The whole concept of SE on optical networks doesn't make sense in the
first place.

-- David

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From: gmpls gmpls <[email-masked]>
Date: Mon, 15 Apr 2002 07:13:56 -0700 (PDT)

Thanks Zhi for ur clarification.
This has led to another question
Is optical network providing service other than UNI
clients. If not, why do we have to provide other style
of reservation, which is not going to used at all?

Regards

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From: Sudheer Dharanikota <[email-masked]>
Date: Mon, 15 Apr 2002 11:08:08 -0700

Hi David:

> How could you conceivably have two time-slices share resources?  Or two

Only to imply that a time-slice can be allocated to one of the
*backup* paths when a primary path fails.

- sudheer

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From: Sudheer Dharanikota <[email-masked]>
Date: Mon, 15 Apr 2002 11:23:55 -0700

> of reservation, which is not going to used at all?

Hi gmpls gmpls:

UNI is at the unser-to-network interface. It does not
talk about inside the network, which is what we are
talking about in SE style.

Also, if have some questions regarding OIF UNI
please post it in oif mailing list.

Regards,

sudheer

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From: David Charlap <[email-masked]>
Date: Mon, 15 Apr 2002 15:58:29 -0400

Sudheer Dharanikota wrote:
> David Charlap wrote:
>>
>> What's the point?
>>
>> In an optical network, you are signaling wavelengths or time
>> slices.  How could you conceivably have two time-slices share
>> resources?  Or two wavelengths?
> 

That's not the definition of SE style.  SE style may be used for many
things other than signaling backup paths.

To assume that SE style can only be used in the way you want is
unwarranted.  You may end up with undefined behavior if you do.

If you need a mechanism for explicitly indicating which LSPs serve as
backups for others, then you should use a mechanism that is meant to do
this.  If none exists, then you should define one and use this working
group to make it into a standard.

Unilaterally assigning a new and undocumented meaning to an existing
construct is never a good idea.

-- David

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From: Curtis Villamizar <[email-masked]>
Date: Wed, 24 Apr 2002 01:25:58 -0400

> construct is never a good idea.

Delayed response...

What SE is used for in MPLS/TE is always to indicate that resources
are shared.  It doesn't signal any kind of reroute but the sharing is
among the primary and backup in local protection beyond the merge
point (not applicable to fully disjoint paths from ingress to egress)
or among the primary and another path that will be used in a
make-before-break fashion.

It makes perfect sense to reuse the same lambdas on some legs to
overlap in make-before-break fashion and turn off one laser at the
ingress (for lambdas) and turn on another and have a (very near) no
impact reroute that does not require a complete teardown before the
setup.  It also makes sense to do a local repair this way.  It also
may be applicable to time slices if there was a way to send nothing on
time slice on the one path not in use at any given time in the
transition.  This would be like sending empty sonet frames on one of
two OCx and having an intermediate pick the non-empty frames from
either or two ingress OCx and send them out another OCx.  This is very
APS like if used for repair in the TDM context.  This clearly involves
too much inspection for burst switching and is more like what a router
or ADM can do and less like what optical burst switching can do.

IMHO, the UNI is useless so direct discussion to OIF.  Or devnull or
anywhere but the IETF.

Curtis