Subject: [Pce] different version support for PCC-PCE communication?

From: Alia Atlas <[email-masked]>
Date: Mon, 25 Apr 2005 01:22:13 -0400

There are naturally requirements for extensibility and policy 
considerations such that different constraints can be specified - and some 
such constraints may not be considered at the initial time of protocol design.

For incremental deployability of such new constraints, there may want to be 
a requirement describing the required interactions to handle unknown 
constraints and capabilities.  For instance, does the PCE advertise 
capabilities that define all the constraints the PCC is allow to use?  In 
such a case, if a PCC doesn't understand a capability, the PCC should be 
able probably to ignore one capability and consider the others.

Thoughts?

Alia

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From: JP Vasseur <[email-masked]>
Date: Mon, 25 Apr 2005 07:00:10 -0400

Hi Alia,

On Apr 25, 2005, at 1:22 AM, Alia Atlas wrote:

> considerations such that different constraints can be specified - and 
> some such constraints may not be considered at the initial time of 
> protocol design.
>
> For incremental deployability of such new constraints, there may want 
> to be a requirement describing the required interactions to handle 
> unknown constraints and capabilities.  For instance, does the PCE 
> advertise capabilities that define all the constraints the PCC is 
> allow to use?  In such a case, if a PCC doesn't understand a 
> capability

or by policy, "does not allow for requesting path computation with such 
constraint" (e.g. case of inter-domain).

> , the PCC should be able probably to ignore one capability and 
> consider the others.
>
> Thoughts?
>
> Alia
>
>

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From: Alia Atlas <[email-masked]>
Date: Mon, 25 Apr 2005 08:31:21 -0400

Hi JP,

At 07:00 AM 4/25/2005, JP Vasseur wrote:
>>For incremental deployability of such new constraints, there may want to 
>>be a requirement describing the required interactions to handle unknown 
>>such a case, if a PCC doesn't understand a capability
>
>>, the PCC should be able probably to ignore one capability and consider 
>>the others.

I agree that the handling of different constraints may depend not only on 
the PCC and PCE's abilities to understand them but also on the policy 
configured at the PCC and PCE.  The question then becomes what defaults and 
interactions are appropriate?  Perhaps the first step is to think about the 
different usage scenarios and what would be desirable to do in each one; 
then we could see what common cases fall out.

Alia