Subject: [Pce] I-D ACTION:draft-ietf-pce-pcep-xro-03.txt

From: [email-masked]
Date: Wed, 20 Feb 2008 11:15:01 -0800 (PST)

A New Internet-Draft is available from the on-line Internet-Drafts 
directories.
This draft is a work item of the Path Computation Element Working Group of the IETF.

	Title		: Extensions to the Path Computation Element Communication Protocol (PCEP) for Route Exclusions
	Author(s)	: E. Oki, A. Farrel
	Filename	: draft-ietf-pce-pcep-xro-03.txt
	Pages		: 16
	Date		: 2008-2-20
	
The Path Computation Element (PCE) provides functions of path 
   computation in support of traffic engineering in Multi-Protocol 
   Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. 
    
   When a Path Computation Client (PCC) requests a PCE for a route, it 
   may be useful for the PCC to specify, as constraints to the path 
   computation, abstract nodes, resources, and Shared Risk Link Groups 
   (SRLGs) that are to be explicitly excluded from the computed route. 
   Such constraints are termed route exclusions. 
    
   The PCE Communication Protocol (PCEP) is designed as a communication 
   protocol between PCCs and PCEs. This document presents PCEP 
   extensions for route exclusions.

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From: "Fabien VERHAEGHE" <[email-masked]>
Date: Thu, 28 Feb 2008 14:01:10 +0100

Hi,

I have one question for XRO draft authors.

The AS number hop encoding defined in XRO draft is slightly different than
the one described in RFC3209 which is also used in PCEP ERO, IRO.

I guess there is a need for 4 bytes AS number but don't we need to keep
consistent the AS hop format for all kind of routes?

Thanks
Fabien

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---

From: "Adrian Farrel" <[email-masked]>
Date: Thu, 28 Feb 2008 15:17:48 -0000

Hi Fabien,

My personal thoughts are:
1. RSVP-TE and PCEP are not the same protocol.
   It may be convenient for them to have common encodings, but
   this is not a requirement.
2. The PCEP ERO, IRO, and XRO should have common encodings.
3. Since we are building a new protocol and can do it, we should
    be future-proofed against the likely 4 octet AS number.

The consequence of this is that we should take the 4 octet AS number into 
PCEP as standard. A non-consequence is that RSVP-TE needs to be fixed to 
support 4 octet AS numbers (this will be required at some stage, but is not 
required as a consequence of this work in the PCE working group).

Cheers,
Adrian

---

From: "Fabien VERHAEGHE" <[email-masked]>
Date: Thu, 28 Feb 2008 17:02:34 +0100

Hi Adrian,

Thanks for the fast reply.

Does it mean you think draft-ietf-pce-pcep-10.txt should be changed to reuse
hop encoding as defined in XRO draft rather than the one in RFC3209/RFC3477?

I have noted another difference which is that unnumbered interface hop is
type 3 draft-ietf-pce-pcep-xro-03.txt whereas it is type 4 in
draft-ietf-pce-pcep-10.txt (i.e. RFC3477).

Would it make sense to proceed as follows:
1. Reusing exactly the same Hop subobject in XRO than in
draft-ietf-pce-pcep-10.txt (i.e. the one defined in RFC3209/RFC3477 and
maybe RFC3473 if we want to authorized label object in XRO).
2. Defining a new extended-AS subobject for 4 bytes AS number.
3. Stating in XRO draft that extended-AS subobject can be used also in PCEP
ERO,RRO and IRO.

I see 3 advantages:
1. It alleviates XRO draft since it requires only 1 hop subobject
definition.
2. It Does not require any change in draft-ietf-pce-pcep-10.txt.
2. RSVP could reuse the same encoding if needed in the future so that Hop
object encoding is perfectly align between PCEP and RSVP.

Best regards
Fabien

> -----Message d'origine-----
> De : Adrian Farrel [mailto:[email-masked]]
> Envoyé : jeudi 28 février 2008 16:18
> À : [email-masked]
> Cc : [email-masked]
> Objet : Re: [Pce] draft-ietf-pce-pcep-xro-03.txt: AS number Hop format
> (possible PCEP last call comment)
> 
> Hi Fabien,
>