Subject: RE : [Pce] WG feedback required on PCE Capability Discovery

From: "LE ROUX Jean-Louis RD-CORE-LAN" <[email-masked]>
Date: Mon, 2 May 2005 10:32:05 +0200

Hi Adrian, 

>Well, OK.
>But let's be really careful about the word Policy.
>It has established meaning in other protocols and it sounds 
>like this is intended to be a different meaning. An example of 
>a Policy by my lights would be "PCCs from this domain are not 
>allowed to ask for paths of this type that cross that domain 
>for this priority traffic except on a Wednesday or when there 
>is an R in the month."

Yes, actually in the current PCE com reqs draft we awkwardly mixed path selection policies and protocol communication policies (see 6.2.3), and, in the context of this PCE capability discovery discussion, I thought you were referring here to the discovery of supported path selection policies...
Note that this will be clarified in next revision (see previous mail sent by Jerry to Ina). 
You are right that discovering such policies, if desired, could require more than just bit flags. 
By the way for simple policies like "the PCE can only serve requests sent by PCCs in its AS", I don't think there is a need for policy discovery, rather the discovery protocol itself must be policed to restrict PCE discovery to authorized PCCs (in the above example restrict PCE discovery scope to a single AS).

Thanks,

JL

>-----Message d'origine-----
>De : Adrian Farrel [mailto:[email-masked]] 
>Envoyé : vendredi 29 avril 2005 13:38
>À : LE ROUX Jean-Louis RD-CORE-LAN; [email-masked]
>Objet : Re: [Pce] WG feedback required on PCE Capability Discovery
>
>
>Hi JL,
>
>Basic agreement.
>
>Two small points.
>
>> >(Option 3 is not such a burden since it is a request/response 
>> >interaction and that is exactly what the PCE-PCC communications 
>> >protocol does best.)
>>
>>Yes, but this may lead to multiple PCC-PCE crankbacks (ie
>> a PCC may have to try various PCEs before to find the  appropriate 
>>one)
>
>Yes and no.
>Yes, the first time.
>No subsequent times.
>That is, we may assume that a PCC will retain the PCE 
>capabilities information regardless of how it is propagated. 
>Certainly you wouldn't suggest that a PCC that receieves this 
>information through an IGP would have a problem deciding whihc 
>PCE to contact because it hasn't received an update for 10 minutes!
>
>>>Note that the PCE-PCC comms draft currently says that items like 
>>>Policies must be advertised as part of the PCE capabilities. These 
>>>could be non-trivial and many in number.
>>
>>Most of the policies (constraints, criterias...) can IMHO be encoded 
>>using flags...
>
>Well, OK.
>But let's be really careful about the word Policy.
>It has established meaning in other protocols and it sounds 
>like this is intended to be a different meaning. An example of 
>a Policy by my lights would be "PCCs from this domain are not 
>allowed to ask for paths of this type that cross that domain 
>for this priority traffic except on a Wednesday or when there 
>is an R in the month."
>
>A
>
>

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