Re: [sfc] Progression of use case documents in the SFC WG

["Jeffrey Napper (jenapper)" <[e-mail]>]

I agree here (+1 to the chairs) and would like to respond to some specifics.

[further responses inlined below]

Cheers,
Jeff

From: "Ken Gray (kegray)" <[e-mail]<mailto:[e-mail]>>
Date: Thursday, March 27, 2014 at 5:28 AM
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "Jim Guichard (jguichar)" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: [sfc] Progression of use case documents in the SFC WG

I'd give a +1 to the chairs …

If there is going to be more than one document (and we seemed hell bent on more than one at the BoF … we could, as a group, settle on "a small number"), that they have some focus.

I don't find the focus or organization described by the chairs onerous - in fact, GIVEN that we have the liaison(s) in place and that they do want a voice here, and that at least one of them has a "domain focus" I find it logical to start with broadband and develop use cases in a set of non-trivial domains.

[JN] I also agree with the point made elsewhere in the thread that combining the general and specific use case documents will produce a too long document, which is why I support a limited number of focused, separate domain documents.

They had to define "a small number" …or "a small number" becomes a big number.  Now we know how many "a small number" is.

If draft–liu is stripped of enough content by the categorization of the "small number" it's efficacy should be questioned.  To your specific point, as a group we can decide on moving the specific text you mention back to Problem or otherwise re-home it.  It shouldn't be the sole reason draft-liu exists.

I would have gone a bit further than the chairs, frankly.

There is SO much use case literature out there right now, I frankly don't want to see the IETF repeat any more than it has to.  I would hazard that most of us have read these things before in one of several forums.

[JN] I believe the main point is to generate a smallish set of requirements (the smaller the better of course) within a deadline. There is plenty of use case literature, and the value of the use case documents here is to produce a concrete set of requirements directly related to the specific use cases so that we can come to a consensus on whether a solution meets all the requirements. Equally important is that the chairs put a deadline on production of use case/requirements documents so we can move on to solutions. To that end, I applaud the chairs for moving forward.

So, IMO, the use cases should provide support for the problem statement and the development of a proposed header functionality (solution), and as such should illustrate significantly unique requirements …so that we can assess the efficacy of the proposed solutions.  I hope the "owner by area" described by the chairs will take on the responsibility of making sure that their examples are significantly unique for  consideration and addressable in the solution.

[JN] Speaking for our use case only, we are considering additional use cases with the caveat that each one must provide new requirements or weaknesses to current approaches. It keeps a definite reasonable limit on the number of use cases. Our approach is to start with simple cases and add complex cases where/if needed.

Because their work represents the work of many (whole organizations) and is hopefully further distilled by the author here into unique examples, in fairness their contributions should probably be credited to "various" with a nod to their organization.

[JN] We are trying to work with other representatives in 3GPP individually. IIRC, they are developing a use case document, but it is not complete. We are of course, happy to give credit where applicable. :)

And, because these use cases have been reviewed in other forums by many people, the process should be more expeditious.

[JN] You'd think that, but some of the other documents I've seen don't follow the simple approach of each successive use case providing new requirements unique to the previous cases in the document. They simply divide up the requirements of a set of similar use cases.



From: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Date: Thursday, March 27, 2014 3:07 AM
To: "Jim Guichard (jguichar)" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: [sfc] Progression of use case documents in the SFC WG

Dear chairs,

Some comments below:

·         The proposed actions are not aligned with the feedback received in this thread (Progression of use case documents within the SFC working group). Answers to that poll are in favor of having a generic use case document. IMHo, it is not fair to ignore what was voiced for by wg members in the mailing list as part of a formal call with clear questions.

·         Some of the text that was adopted by the WG as part of the Problem Statement (use case as part of the Problem statement) has been moved to the generic use case. That text is governed by this charter text: “1. Problem Statement: This document will provide a summary of the
problem space to be addressed by the SFC working group including
example high-level use cases. Additionally, the working group will
normalize nomenclature and definitions for service function chaining.”. What to do for that text?

·         Having the generic use case document and some few detailed ones do not conflict. It is only a matter of scoping.

Given what is stated above, I disagree with your proposal.

If I have to choose (again), I would vote for having one single use cases document. Having one single document will help focusing on core aspects and would simplify the wg activity: review, last calls, etc.

Cheers,
Med

De : sfc [mailto:[e-mail]] De la part de Jim Guichard (jguichar)
Envoyé : mercredi 26 mars 2014 18:54
À :[e-mail]<mailto:[e-mail]>
Objet : [sfc] Progression of use case documents in the SFC WG

WG:

In a message back in January, we (the chairs) proposed that the SFC WG handle the topic of use case documents as follows:

1) Have the WG develop one use case document that documents a small number of representative use cases.  The document presented by Hongyu Li at the Vancouver BOF could serve for this purpose
(http://datatracker.ietf.org/doc/draft-liu-service-chaining-use-cases).

3) For additional use cases not covered in 1) above, allow for a small number of documents that are applicable to specific
environments (e.g.  mobility, data center, broadband, and so forth.) These documents would provide more detailed information and applicability of SFC to these specific environments, and would need to go beyond what is covered in the general use case document (1). Note that it is not the intention to have every potential use case documented.

Since then, and based on the presentations/discussion in London, it appears that we have a number of documents that warrant being developed as standalone documents. Specifically:

1) A use case document on mobility, e.g., http://datatracker.ietf.org/doc/draft-haeffner-sfc-use-case-mobility/

2) A use case document on Data Centers, e.g., http://datatracker.ietf.org/doc/draft-kumar-sfc-dc-use-cases/

3) Possibly a use case document on Broadband scenarios. However, use cases from a broadband perspective are being developed in the BBF (see the liaison statement at https://datatracker.ietf.org/liaison/1304/). We also have http://datatracker.ietf.org/doc/draft-meng-sfc-broadband-usecases/.  It does not seem appropriate to adopt a WG document on the topic of broadband (at least at this time) without clarifying the relationship between draft-meng-sfc-broadband-usecases and the BBF work. In addition, we would need to understand why two efforts — one in BBF and one in the IETF -- on the same topic would be appropriate. Hence, at the present time, we do not intend to adopt a WG document on broadband scenarios, and expect to receive primary guidance on this topic from the BBF.

That leaves: http://datatracker.ietf.org/doc/draft-liu-sfc-use-cases/, a more general document. But that document includes text on three topics that would be covered in more detail elsewhere (broadband, mobile, and DC). While this document could contain pointers to the other documents, that leaves the document with very little standalone content -- raising the question of what should be done with it, or what content it could incorporate in order to be worthwhile as a standalone document.

Thus, the chairs recommendation at this time is:

1) Call for WG adoption of draft-haeffner-sfc-use-case-mobility-00.txt and draft-kumar-sfc-dc-use-cases-00.txt as WG documents (target: informational).

2) Defer action on draft-liu-service-chaining-use-cases<http://datatracker.ietf.org/doc/draft-liu-service-chaining-use-cases>  and draft-meng-sfc-broadband-usecases<http://datatracker.ietf.org/doc/draft-meng-sfc-broadband-usecases/> per the above discussion.

Does this make sense?

Jim & Thomas