Re: [DMM] Call for adoption of draft-hmm-dmm-5g-uplane-analysis-02 as DMM WG document

[David Allan I <[e-mail]>]

Assuming it does somehow fit into the charter, I would still like to see significant modifications to make the purpose of the document in the context of IETF and DMM clear before the document was adopted.

Regards
Dave

From: Shunsuke Homma <[e-mail]>
Sent: Friday, November 16, 2018 3:14 AM
To: David Allan I <[e-mail]>; [e-mail]; Shunsuke Homma <[e-mail]>
Subject: Re: [DMM] Call for adoption of draft-hmm-dmm-5g-uplane-analysis-02 as DMM WG document

Hi Dave,

Thank you for details of your thought about charter.

Firstly, we've understood that only 3GPP can decide criteria for evaluation of candidate protocols. The evaluation aspects described in the section 5 are just references from IETF view points, and this draft will never force 3GPP folks to use the aspects for thier evaluation. If the description "Our conclusion here~" is not appropriate, we can change it.

Regarding the charter, in my understanding, this document would be contribution for work "Distributed mobility management deployment models and scenarios". As you know, 3GPP 5G architecture allows to distribute UPFs, and it means that the 5G architecture potencially supports distributed mobility management. 3GPP architecture is widly used in the world, and clarifying the requriements and issues of the 5G architecture as a reference model would be corresponded to the scope of DMM. It would be help for further study in DMM WG.

In addition, the charter describes "The working group may decide to extend the current milestones based on the new information and knowledge gained during working on other documents listed in the initial milestones. Possible new documents and milestones must still fit into the overall DMM charter scope as outlined above.",  and we can extend the milestones if it is needed.

Therefore, I believe this document is in the scope of DMM, and this work will help for DMM.

Best regards,

Shunsuke

2018年11月16日(金) 5:03 David Allan I <[e-mail]<mailto:[e-mail]>>:
Hi Shunsuke:

First off I think there is a charter problem in that there are no milestones that are not 18 months out of date.  That is independent of draft-hmm.

If I look at the list of topics that the charter suggests the WG could produce draft on I don't see a fit with any of them. The closest being:
        Distributed mobility management deployment models and scenarios:
         describe the target high-level network architectures and
        deployment models where distributed mobility management
        protocol solutions would apply

However the charter describes a DMM solution as one being:
        "The IETF Distributed Mobility Management (DMM) working group
        (WG) specifies solutions for IP networks so that traffic between mobile
        and correspondent nodes can take an optimal route."

I cannot connect the content of draft-hmm with these objectives.  At the moment it appears clear that the draft has been written for the purpose of advocacy explicitly to 3GPP of user plane protocols.  I suppose it could be claimed to describe parts of the 5G architecture and that is useful, but a lot would need to be expunged from the draft before that part of it was useful to capture for archival or educational purposes.

The draft's primary claim to fame from what I can tell is the conclusion that support for SSC mode 3  would benefit from a UP change to permit mp2p tunneling. Now I will certainly not claim to be an expert, and was not in the room when any of this was discussed in 3GPP or codified (full disclaimer, never attended a meeting). But my understanding of SSC mode 3 and branching is that this is a mechanism to support a network initiated change of UPF in a make before break fashion and is likely only a temporary situation.  The actual practice being to set up the branch point and new UPF, and the UE lets all old prefix correspondent sessions quiesce, while initiating all new sessions with the new prefix, at which point connectivity to the old UPF can be torn down .   As such I would consider suggesting this is a serious problem that requires a complete UP change from RAN to DN is a questionable and possibly dangerous conclusion.  I would also observe that any sort of solution to mp2p tunneling for the 5GC does not appear to be part of DMM's objectives as described in the charter; it claims to reduce state for a rare operational procedure, and is not a solution to optimal routing of UE traffic.

I hope this helps
Dave


-----Original Message-----
From: Shunsuke Homma <[e-mail]<mailto:[e-mail]>>
Sent: Thursday, November 15, 2018 1:19 AM
To: [e-mail]<mailto:[e-mail]>; David Allan I <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [DMM] Call for adoption of draft-hmm-dmm-5g-uplane-analysis-02 as DMM WG document

Hi Dave,

Thank you for reviewing our draft and sending your thought for the adoption.

When I reviewed the charter I couldn't find any text to make the draft to be out of scope. Could you please elaborate it with the text in the charter?

Best regards,

Shunsuke


On 2018/11/15 6:52, David Allan I wrote:
> HI
>
> AFAIK 3GPP CT4 is looking for work it can adopt, and has indicated
> that it wishes to perform the analysis itself. When they were directed
> to this document in the recent IETF DMM liaison, it  resulted in a
> liaison reply clearly indicated they would define their own criteria.
>
> https://datatracker.ietf.org/liaison/1590/
>
> However in the draft it states in the introduction: "However we
> believe that to provide adequate information for 3GPP, we need to
> clearly understand what the current user plane protocol is in Release
> 15, and architectural requirements for the user plane." And in the
> conclusion "Our conclusion here is that we suggest the UP protocol
> study work in 3GPP takes into account the evaluation aspects described
> in Section 5.", there is more, but I do not feel a need to be pedantic about it.
>
> So the purpose of this draft seems to explicitly be to do work for
> 3GPP that they have explicitly said they DO NOT WANT.
>
> At the same time I do not see anything in the charter that suggests we
> should be doing this work either.  It would appear to have little to
> do with DMM's chartered direction.
>
> As such I am opposed to adoption of the draft.
>
> Cheers
>
> Dave
>
>
>
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> [e-mail]<mailto:[e-mail]>
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