Re: Failure definition w.r.t. SONET/SDH and Protection/Restoration

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

Hi Amit,
                it seems to me that we are mixing different issues here (a
part from the fact that may be we need to change the subject of the
thread).

First point I think that link protection and path protection leads to
different problem.

In case of link protection it is quite simple to solve the issue; data
plane protecting link is hidden to the control plane and a hold-off timer
is used in order to separate data plane protection mechanism from control
plane restoration.

In case of path protection thing are different and I think are not solved,
or at least not solved in CCAMP/ITU-T.

The main issue I see in this field is the interworking between MS-SPRing
protection and control plane restoration.

It is a matter of fact that MS-SPRing is one of the most used inherent
protection scheme in SDH network but up to now we don't have a 'standard'
way to let MS-SPRing to interwork with control plane restoration scheme
(e.g. timeslot interchange and squelching problem)

I've again to mention the WG chair here and ask him if this kind issues are
in the scope of the CCAMP.

Regards

Diego





Amit 70405 <AmitG@huawei.com> on 25/03/2005 02.41.04

To:    Adrian Farrel <adrian@olddog.co.uk>, Igor Bryskin
       <i_bryskin@yahoo.com>
cc:    Diego Caviglia <Diego.Caviglia@marconi.com>, ccamp@ops.ietf.org,
       Sasha@AXERRA.com

Subject:    Re: Failure definition w.r.t. SONET/SDH and
       Protection/Restoration


Hi Adrian & Igor,
   But there is one issue with this multilayer protection.
   Say in the case if the link gets broken, and the lower layer protection
has succeeded.
   In this case, should the control plane(higher layer) be notified by the
lower layer of link??

   If yes than it has following consequences:
   - As control plane is unaware of any failure, control plane will
continue to setup new connections on the failed.
   - This may not be a good thing to do.
   - Some means may be needed to avoid this link in Path computation.

   If no than following are the consequences:
   - Control plane too will go ahead with its protection mechanism.

   Let me know your view.
Regards,
Amit.


----- Original Message -----
From: Adrian Farrel <adrian@olddog.co.uk>
Date: Thursday, March 24, 2005 7:40 pm
Subject: Re: Failure definition w.r.t. SONET/SDH and Protection/Restoration

> Hi Amit,
>
> >    Do you mean to say that Data plane & Control plane protection
> shouldbe independant of each other??
>
> No, I mean that they MAY be independent.
> In particular, if you are using the control plane *and* the data
> plane to
> manage protection on the same set of resources you are bound to
> get in a
> horrible mess.
>
> Seems more reasonable that you would apply data plane protection
> first and
> then apply control plane protection at a higher level.
>
> >    If so, in case of MSP protection in SDH,
> >     Control plane should not have any control over the resource pool
> >      used for MSP switch.
> >    This may lead to lot of unused resource in the network.
>
> It is certain that each layer of protection that you install MAY
> result in
> unused resources. Building multiple layers of protection will,
> therefore,potentially build up more and more unused resources. It
> is the job of
> CCAMP to produce the tools that allow operators to build the
> protectionschemes that they want. It's not really our business to
> tell them which
> schemes to build and when.
>
> Cheers,
> Adrian
>
>