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

[Jerome Moisand <[e-mail]>]

Hi Linda,

The subscriber management function in a BNG is clearly a Service Function (and a Service Classifier) on its own right. All the BBF use cases are based on such premise, this is the starting point of the service chains. We’re in clear agreement here, and I don’t think we need a new draft to repeat this point.

I still do not understand how DS-Lite and MAP are related to service chaining. There is no need to do any new form of traffic steering to perform such functions. Yes, sure, the CPE needs to do its part of the work, according to corresponding IETF documents (e.g. as defined in the IETF Softwire WG), but again, where is the service chaining? I do not believe that the Softwire group expressed any need for further mechanism besides what they defined. Sorry, I don’t quite get it. I can see how service chaining and IP v4/v6 gets intertwined for the CGNAT approach though, we do agree on this one. If you think there is more than that, then please contribute to BBF (SD-326, SIMR group). We’d welcome more use cases while the Study Document is being refined.

In general, the point remains that it would be greatly appreciated to discuss both service chaining and IPv4/v6 transition use cases, broadband network architecture and nodal requirements in the BBF context, and liaise to IETF when appropriate (e.g. need for protocol work). Same for CPE discussions, including Cloud-CPE. We’re all stretched pretty thin, and could really benefit from discussing in the most appropriate context without undue duplication across std bodies.

Tx
Jerome


From: [e-mail] [mailto:[e-mail]]
Sent: Monday, March 31, 2014 3:58 AM
To: Jerome Moisand
Cc: [e-mail]; sfc
Subject: 答复: Re: [sfc] Progression of use case documents in the SFC WG


Hi, Jerome

  As a co-author of draft-meng, maybe I have to highlight some points in our draft. As you mentioned:
          Side note: draft-meng-sfc-broadband-usecases seems to cover two topics:
1.       a basic form of service chaining (‘BNAS’ –I guess this means BRAS/BNG- to CGNAT) which is already covered by BBF use cases
2.       then a lot of material about IP v4/v6 transition matters (DS-Lite, MAP, etc), which doesn’t seem to have a direct relationship with service chaining per se. Anyhoo, it turns out that there is another BBF work item in this respect, so corresponding material should find its rightful place.

  It seems that I hold the different opinion of you.  CGNAT is just one SFC use case in Broadband Network per se, as well as NAT64 and other IPv4/v6 transition technology. They are distinctive from each other and they go through different SFC. So we put them together in this draft.  And here, we also want to mention is Subscriber-management function in BNG, which is suggested to be referred as a SF, because BNG's capacity of subscriber is also a bottleneck, it seems reasonable to consider Subscriber-management function as a SF.
  In addition, after listing and comparing them, it turns out that we can not only deploy SFC Domain between BNG and CR, but also we can consider a SFC Domain deployment between CPE and BNG, which is called unify home router in our draft. It means that CPE only support simple L2/L3 functionalities including encapsulating and decapsulating. Wherever the traffic go is decided by the SFC Domain. This seems a bit like your Cloud CPE.
  Also, we propose some considerations (e.g. standalone mode, directly connecting mode  and pool consideration). As for standalone mode and directly connecting mode, which are the main two architecture in IPv6 transition deployment, we think maybe this consideration can  introduce into SFC architecture. As for more details such as pool management, we just give our proposal and the reason for this proposal is for steering the income traffic.

Hope I have clearly highlighted our draft : )

Many thanks!
Linda


Jerome Moisand <[e-mail]<mailto:[e-mail]>>
发件人:  "sfc" <[e-mail]<mailto:[e-mail]>>

2014-03-27 20:55

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"[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>

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







Agreed with the chairs proposal.

There is no point duplicating work performed by other std bodies, it is much better to use it as a an input, while letting specialized discussions occur between groups of corresponding specialists. BBF leverages IETF work all the time, well, it’s time to have IETF leverage BBF work.

Being co-editor of the BBF work, I’ll make sure that new use cases identified by BBF will be communicated in a reasonably timely fashion to IETF. We do have a few new ones in the works. And we’ll work with the authors of draft-meng-sfc-broadband-usecases to consolidate with BBF work.

Tx
Jerome

Side note: draft-meng-sfc-broadband-usecases seems to cover two topics:
1.       a basic form of service chaining (‘BNAS’ –I guess this means BRAS/BNG- to CGNAT) which is already covered by BBF use cases
2.       then a lot of material about IP v4/v6 transition matters (DS-Lite, MAP, etc), which doesn’t seem to have a direct relationship with service chaining per se. Anyhoo, it turns out that there is another BBF work item in this respect, so corresponding material should find its rightful place.


From: sfc [mailto:[e-mail]] On Behalf Of Ken Gray (kegray)
Sent: Thursday, March 27, 2014 8:28 AM
To: [e-mail]<mailto:[e-mail]>; Jim Guichard (jguichar); [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.

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.

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.

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.

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




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_______________________________________________
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