Subject: Re: GMPLS for MS-SPRing

From: "Diego Caviglia" <[email-masked]>
Date: Fri, 14 Oct 2005 16:21:34 +0200

Hi Julien,
           is always a pleasure to discuss this topics with you.

You are right and a clarification is definitely needed here.
Basically Ring ID parameter is a common identifier for all the TE links
belonging to the same ring.

In such a way, in a no-control plane/pre-GMPLS scenario, from a management
plane point of view it is possible to
discern if a given node belongs to a given ring by checking its Ring ID.

In an advanced scenario, where a control plane (GMPLS based) is in place
"between" data and management plane, the Ring ID parameter keeps on
doing the same function of making possible the association of a given TE
link with the ring it belongs to.

Why is this information needed at control plane level? Think of a routing
protocol deployed over control plane, say GOSPF-TE. When we come at dealing
with MSSPRING inherent requirements that control plane has to be compliant
with, there are spring related informations that a routing protocol has to
flood over the network (as opaque) to make possible correct operation.
Among them there could be (depending on the strategy that'll be followed)
the information about a TE link as belonging or not to a ring and, if yes,
to which ring. In this case Ring ID serves the purpose.
For a ingress node running Path Computation Engine it is important to know
this attribute of a TE link to take special routing decisions or to try to
satisfy given requirements involving MSSPRING traversing.

In addition, ring ID information could be used if some information
interests only the TNE's belonging to a given ring and has to be flooded
only to the TNEs in that ring. In this case Ring ID could be used by a TNE
belonging to a ring to check if its OSPF neighbor belongs tho the same ring
and hence if a given LSA has to be sent to it or not.

These are examples of possible usage of Ring ID within control plane. Apart
from these specifc uses, there could be other cases to be defined where a
similar identifier is needed. Of course it depends on which strategy is
chosen to handle MSSPRING management and requirements from control plane.

Hope this clarify.

Best Regards

Diego

"MEURIC Julien RD-CORE-LAN" <[email-masked]>@ops.ietf.org
on 14/10/2005 13.58.16

Sent by:    [email-masked]

To:    "Diego Caviglia" <[email-masked]>
cc:    "ccamp" <[email-masked]>

Subject:    GMPLS for MS-SPRing

Hello Diego.

I have just read your draft-caviglia-ccamp-gmpls-msspring-req-00.txt about
GMPLS requirements for MS-SPRing. I am glad to see you have again a
pragmatic approach to ease operators' migration from legacy SDH to GMPLS.

In paragraph "2.1 LSP Set-Up", you mention a "RingId" required by the
management plane and useless for the data plane itself. I am not
questionning this necessity (I am not a management expert), but I do not
really understand why it should be handled by the control plane. I imagine
this is related to communication between control and management, but a
clarification may be required here.

Thanks

Julien

---

From: Igor Bryskin <[email-masked]>
Date: Fri, 14 Oct 2005 07:39:55 -0700 (PDT)

Hi Diego,

One thing that I'd suggest adding to your draft is
ability to compute and signal LSP paths in terms of
rings rather than in terms of links, and let ring
border LSRs to expend the paths - provide paths within
the rings. This mechanism is especially handy when
there is a need for path-segment recovery on per-ring
basis.

Igor

--- Diego Caviglia <[email-masked]> wrote:

> "MEURIC Julien RD-CORE-LAN"
> <[email-masked]>@ops.ietf.org
> on 14/10/2005 13.58.16
> 
> I have just read your
> draft-caviglia-ccamp-gmpls-msspring-req-00.txt about

		
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---

From: George Swallow <[email-masked]>
Date: Fri, 14 Oct 2005 14:32:38 -0400

> there is a need for path-segment recovery on per-ring

Perhaps I'm reading too much into this as I note that you only talked
about signalling and not routing.

But if you want to accurately show the state of the ring (e.g.
bandwidth), then you have to advertise each segment of the ring.

I worked out a lot of the details quite a long time ago.  Be glad to
help out on the protocol part.

...George

========================================================================
George Swallow             Cisco Systems                  (978) 936-1398
                           1414 Massachusetts Avenue
                           Boxborough, MA 01719

---

From: Igor Bryskin <[email-masked]>
Date: Sat, 15 Oct 2005 05:22:31 -0700 (PDT)

Agree. Note that I was talking about signaling and *path computation*. The laterr cannot be performed without proper advertisings
 
Igor

...George

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