RE: [Pce] Update on draft-ietf-pce-policy-enabled-path-comp

["JACQUENET Christian RD-DDEV-REN" <[e-mail]>]

Adrian,

Pleasure's all mine :-) Don't expect further comments from the "IPSF", but I'll let individuals who are also involved in the IPSF comment further if they want to.

Cheers,

Christian. 

-----Message d'origine-----
De : Adrian Farrel [mailto:[e-mail]] 
Envoyé : jeudi 11 octobre 2007 14:10
À : JACQUENET Christian RD-DDEV-REN
Cc : Thomas Walsh; JP Vasseur; [e-mail]; Lou Berger; Igor Bryskin; Dimitri Papadimitriou; [e-mail]
Objet : Re: [Pce] Update on draft-ietf-pce-policy-enabled-path-comp

Christian,

Many thanks for a good review and useful comments.

Can I assume that there are no further comments coming specifically from the IPSphere Forum?

Authors, can you tell me whether the scope of comments here are large enough to justify a new revision before working group last call? It seems to me that the answer should probably be "yes", but I'm open to persuasion.

Thanks,
Adrian

----- Original Message -----
From: "JACQUENET Christian RD-DDEV-REN" 
<[e-mail]>
To: "JP Vasseur" <[e-mail]>; <[e-mail]>; "Lou Berger" 
<[e-mail]>; "Igor Bryskin" <[e-mail]>; "Dimitri Papadimitriou" <[e-mail]>; <[e-mail]>
Cc: "Thomas Walsh" <[e-mail]>
Sent: Tuesday, October 09, 2007 12:47 PM
Subject: RE: [Pce] Update on draft-ietf-pce-policy-enabled-path-comp


Dear all,

Please find herein my comments, which are *not* on behalf of the IPSF - only personal :-) 1. General:

I think this is a very useful document that clearly identifies the advantages of policy-based path computation management in PCE environments. 
Nevertheless, I would encourage a refined organization of the document, which would distinguish between the framework (current sections 2.1, 4 and 5 basically), the requirements (section 3, but also part of the text that relates to scenarios) and use cases or scenarios (sections 2.2.x, a bit of sections 7 and 8).

2. Section 2.1, page 5:

The introductory sentence of the third paragraph implicly indicates that PCE may very well behave as either a PDP (makes decisions to be applied by PCC clients for example) or a PEP (applies decisions possibly made by PCC clients and/or other PCE components). I think this is one of the very key notions introduced by this draft, and would therefore suggest an introductory section that would elaborate on this heuristic, possibly after the reminder about basic concepts of policy-based management.

3. Section 2.1, page 6:

The last sentence of the first paragraph is slightly confusing: I don't think the "or" is exclusive, that is, provider-defined policies might very well be real time.

4. Section 2.2.3, page 11:

What's a policy-enabled PCC? A PCC that either embeds a PEP, a PDP or both? 
I think this should be elaborated, possibly in the Terminology section. Note also that the last sentence of the page mixes the notions of "making decision" and "apply user or service-specific policies": since the text introduces a kind of causality effect (the PEP embedded in the PCC enforces user or service-specific policies, which seems to result in soliciting the PDP embedded in the PEP to make decisions about the scope of constraints that need to be taken into account for path computation purposes), I would suggest a kind of flow diagram that could possibly elaborate on the corresponding chronology.

5. Section 2.2.3, page 12:

Related to the comment above, the sentence "when deciding..." of the first paragraph may also suggest the activation of a LPDP capability. I would also elaborate on the possible interactions between the PEP, the PDP and the possible LPDP capabilities that may be embedded in the PCC, assuming a differentiation "a la COPS Client-Type". Who's the destinee of the path computation request in the "once the constraints..." sentence of the same paragraph - the PCE?

In the third paragraph, it seems that (1) The PCC embeds a PDP that makes decisions about constraint-defined policies, (2) Sends a path computation request that conveys the aforementioned policy information towards the PCE, whose embedded PEP (3) Applies the corresponding decisions: is this statement correct? If so, I don't understand why the PCE may "decide to reject the request": that is, from a policy management standpoint, only the PEP of the PCE is solicited in this context, which means that the PEP may not be capable of enforcing the decision, but I don't think the PEP is entitled to *reject* the decision, as part of a decision making process. 
Maybe it's a wording issue.

What would be the conditions to send path computation requests to more than one PCE, aside from an inter-domain context? I'm not sure I understand why the response sent by the PCE-PEP back to the requesting PCC-PDP may indicate *policies*. Unless the document refers to a kind of PCE-inferred feedback PIB (RFC 3571)? In that case, I would elaborate.

6. Section 3, page 15:

The notion of trusted nodes (as introdcued in the third paragraph) should deserve some elaboration, IMHO. The security considerations of this page should either be extended (e.g. preservation of the confidentiality of the information that will be exchanged between a PDP and a set of PDPs), or reference the "true" Security Considerations section of the document, which BTW, rightfully elaborates on such issues.

7. Section 5, page 18:

I don't understand why a protocol like COPS couldn't be used in the case where PEP and PDP are colocated. In any case, a protocol is required to convey the exchanges between the PEP and the PDP...

In addition (last line of the page), it's very unlikely that SNMP will be used to retrieve information from a PIB.

8. Section 5, page 19:

I would suggest some elaboration on the kind of information any given PEP (PCC or PCE) may receive from another *PEP* - is this a typo (i.e. read PDP instead), or does this relate to information different from "policy-related" 
information or else? In a COPS context, multiple Client-Types can certainly reside and coexist within a PEP, but I'm not sure I understand why PEPs would exchange information.

Also, the following paragraph ("any given policy...") is a bit confusing to
me: I don't understand this notion of partial interpretation, and would rather suggest another wording - enforcement instead of interpretation. 
Besides, I'm not sure this paragraph helps in understanding the roles played by PEPs and PDPs.

9. Section 6.1., page 20:

Why *all* PC policy types used in the net *must* be applied? It's a "Client-Type" specific thing, IMHO.

10. Section 6.1., page 21:

In the first paragraph, I don't understand why the PCE selection should be static. Even if the policy enforcement is restricted to the PCE (for path computation purposes), nothing prevents a PEP embedded in a PCC to support the relevant "Client-Type", hence yielding the dynamic identification of the corresponding PCE, by means of the COPS-like OPEN message at PCC bootstrap, for example.

In the third paragraph, the "must" of the first sentence is too strong, IMHO, unless the sentence means that any kind of policy must "encouarge" the support of the corresponding "Client-Types" in the PCC-PEP. If so, I would rephrase.

11. Section 6.2., page 22:

I don't understand why matching repositories would result in a single PC repository, unless further elaboration on such match is provided.

12. Section 6.3, page 23:

Does the figure relate to PCE instead of PCC (same for figure 12)?

13. Section 7.1., page 25:

What's an "objection function"?

14. Typos:

TED = Traffic Engineering Database?

SRLG = Shared Risk Link Group?

Page 16, provide the normative reference associated to LDAPv3.

Page 17, remove the "s" of the very last word of the page.

Cheers,

Christian.


________________________________

De : JP Vasseur [mailto:[e-mail]] Envoyé : lundi 8 octobre 2007 22:36 À : [e-mail]; Lou Berger; Igor Bryskin; Dimitri Papadimitriou; [e-mail] Cc : Thomas Walsh; JACQUENET Christian RD-DDEV-REN Objet : Fwd: [Pce] Update on draft-ietf-pce-policy-enabled-path-comp


Dear WG,

Christian Jacquenet on behalf of IPSphere proposed to make several comments 
on this document.
Christian, could you please send them to the list ?

As agreed, we're still planning to issue a WG LC after this round of 
discussion.

Thanks.

JP.


Begin forwarded message:


From: JP Vasseur <[e-mail]>
Date: September 18, 2007 2:10:12 PM EDT
To: [e-mail], Lou Berger <[e-mail]>, Igor Bryskin 
<[e-mail]>, Dimitri Papadimitriou <[e-mail]>, 
[e-mail]
Cc: Thomas Walsh <[e-mail]>, JACQUENET Christian RD-TCH-REN 
<[e-mail]>
Subject: [Pce] Update on draft-ietf-pce-policy-enabled-path-comp

Dear WG,

>From the WG minutes of the IETF-69 meeting:


12) Update on Policy-Enabled Path Computation Framework
draft-ietf-pce-policy-enabled-path-comp-01.txt (Lou - 5mn) [110]


Lou> ready for Last Call
JP> It sounds ready. Suggestion: offer IPSphere to have a look at the doc 
before last call. JP will be the point
of contact. Asked Ross whether this is a good idea, and Ross agreed. Once 
comments are received, last call.
Adrian> OK, but this is not an indefinite consultation. We want to be able 
to move ahead and complete the I-D
relatively soon.

We have contacted IPSphere and RA WG of IPSphere should provide us some 
feed-back by
mid-October. I have copied Tom Walsh and Christian Jacquenet (chair of the 
RAWG) IPSphere.

Thanks.

JP.




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