Re: [Detnet] WG Last Call: draft-ietf-detnet-mpls-oam-08

[Kiran Makhijani <[e-mail]>]

Thanks Greg.
Personally, I find version fields scary, therefore, wanted to see its value
(e.g. I’d imagine that Node ID field size may need to grow in future or you
need to add some kind of security signature as a new field,  etc.)  and of
course, we cannot possibly list all cases exhaustively.
I guess you could add what you suggested below -  “Version field is needed
if the update to d-ACH can not be introduced in a backward-compatible way”,
similar to [RFC 4385]. Btw, why is it default to 1? 4385 sets it to 0. From
your explanation it does not seem they are related.

With this document is good to go. BTW, I still see -08 in the datatracker (
https://datatracker.ietf.org/doc/draft-ietf-detnet-mpls-oam/).

Cheers,
Kiran

On November 29, 2022 at 5:32:53 PM, Greg Mirsky ([e-mail])
wrote:

Hi Kiran,
thank you for your questions. Please find my notes inlined below under the
GIM>> tag. Please let me know if you have any further questions or
suggestions.

Regards,
Greg

On Tue, Nov 29, 2022 at 3:11 PM Kiran Makhijani <[e-mail]>
wrote:

> Hi authors,
>
> My apologies for late comment. I went through the 08 version of the draft.
> The main concerns of not describing fields are taken care of in 09 in
> response to Tiaran’s comments.
>
> Similar to other fields if you can describe under what circumstances
> version change could be needed, that should clarify when to change this
> field. I am not to familiar with ACH format but if it exists already,
> please provide the reference.
>
GIM>> Providing an exhaustive list of all scenarios that would require a
new value for the Version field seems like a challenge. If I try to
generalize it, a new value for the Version field is needed if the update to
d-ACH can not be introduced in a backward-compatible way. Of course, we can
reference RFC 4385. Where in the text would you suggest it will be helpful?

>
> One thing I am not sure about is PREOF function in OAM vs d-CW. Is it an
> either  d-CW or d-ACH over S-label to carry sequence number or both of them
> can exist?
>
GIM>> Indeed, d-CW and d-ACH carry separate sequence number spaces. A node
that acts on the DetNet Service sub-layer uses the first nibble to
differentiate between d-CW and d-ACH sequence number encodings.

>
> Cheers,
> --Kiran
>
> On November 29, 2022 at 8:49:29 AM, Greg Mirsky ([e-mail])
> wrote:
>
> Hi Janos,
> it appears that all the comments we've received during the WG LC have been
> addressed.  The authors greatly appreciate constructive comments and
> thoughtful suggestions from Ethan and Tianran. Do you see the conclusion of
> the WG LC on draft-ietf-detnet-mpls-oam? We're ready for the next steps in
> progressing this work.
>
> Regards,
> Greg (on behalf of the authors)
>
> On Fri, Nov 11, 2022 at 1:53 AM Tianran Zhou <[e-mail]>
> wrote:
>
>> Hi Grey,
>>
>> Thanks very much for taking my suggestion.
>>
>> I am comfortable with all the changes.
>>
>>
>>
>> 3. “Channel Type - contains the value of DetNet Associated Channel Type.”
>> This is confusing to me at first sight. It seem you are going to define a
>> new channel type. I struggled a while before I understand finally. So it
>> would be nice to revise the text.
>>
>> GIM>> I greatly appreciate your suggestions to clarify the definition of
>> the Channel Type field. Could you kindly propose the clarification making
>> it clearer?
>>
>>
>>
>> ZTR> I am not sure. Maybe “contains -> reuses” could be better? I think
>> in somewhere you would better describe something like, the proposed fields
>> are attached to existing ACHs as shown in figure *.
>>
>>
>>
>> Best,
>>
>> Tianran
>>
>>
>>
>> *发件人:* Greg Mirsky [mailto:[e-mail]]
>> *发送时间:* 2022年11月9日 22:24
>> *收件人:* Tianran Zhou <[e-mail]>
>> *抄送:* Janos Farkas <[e-mail]>; [e-mail]
>> *主题:* Re: [Detnet] WG Last Call: draft-ietf-detnet-mpls-oam-08
>>
>>
>>
>> Hi Tianran,
>>
>> I've uploaded the -09 version of the draft that includes clarifications
>> of fields in the d-ACH as proposed in the text below. I greatly appreciate
>> your feedback and comments about the updates and my responses to your
>> questions.
>>
>>
>>
>> Kind regards,
>>
>> Greg
>>
>>
>>
>> On Fri, Oct 21, 2022 at 12:15 AM Greg Mirsky <[e-mail]>
>> wrote:
>>
>> Hi Tianran,
>>
>> thank you for your questions and comments. Please find responses in-lined
>> below tagged with GIM>>. Attached are the diff and a copy of the working
>> version of the draft.
>>
>>
>>
>> Regards,
>>
>> Greg
>>
>>
>>
>> On Wed, Oct 12, 2022 at 8:38 PM Tianran Zhou <zhoutianran=
>> [e-mail]> wrote:
>>
>> Hi Authors,
>>
>>
>>
>> I read this draft and find it’s useful.
>>
>> I have several suggestions as follows.
>>
>> 1. I am not clear why existing PW OAM cannot be used directly for DetNet.
>> I think there will be text to describe why 4 bytes are added, and also why
>> each field, like node id.
>>
>> GIM>> As described in RFC 8655, DetNet headers may be needed to support
>> DetNet service and forwarding sub-layers. Additional fields are added in
>> support of OAM at the DetNet service sub-layer. Furthermore, we can note
>> that a DetNet PW is more like an MS-PW, where DetNet service sub-layer
>> functions are at the “segment” endpoints. However, DetNet service sub-layer
>> functions operate per packet level (not per segment level). These
>> per-packet level characteristics of PREOF require additional fields for
>> proper OAM packet processing. Would the following update make it clearer:
>>
>> OLD TEXT:
>>
>>    DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in
>>
>>    [RFC4385].  Encapsulation of a DetNet MPLS [RFC8964] active OAM
>>
>>    packet is shown in Figure 3.
>>
>> NEW TEXT:
>>
>>    DetNet OAM, like PW OAM, uses PW Associated Channel Header defined in
>>
>>    [RFC4385].  At the same time, a DetNet PW can be viewed as a Multi-
>>
>>    Segment PW, where DetNet service sub-layer functions are at the
>>
>>    segment endpoints.  However, DetNet service sub-layer functions
>>
>>    operate per packet level (not per segment level).  These per-packet
>>
>>    level characteristics of PREOF require additional fields for proper
>>
>>    OAM packet processing.  Encapsulation of a DetNet MPLS [RFC8964]
>>
>>    active OAM packet is shown in Figure 3.
>>
>>
>>
>> The Node ID field is described in the draft as follows:
>>
>>
>>
>>       Node ID - is an unsigned 20 bits-long field.  The value of the
>>
>>       Node ID field identifies the DetNet node that originated the
>>
>>       packet.  Methods of distributing Node ID are outside the scope of
>>
>>       this specification.
>>
>>
>>
>> 2. There is no description for Level,  Flags, and Session fields on the
>> meaning. I do not know how to use and how to extend.
>>
>> GIM>> Thank you for pointing out too minimalistic descriptions.  The
>> following text is updated in the working version:
>>
>> OLD TEXT:
>>
>>       Level - is a 3-bit field.
>>
>> NEW TEXT:
>>
>>       Level - is a 3-bit field.  Level field is used to cope with the
>>
>>       "all active path forwarding" characteristics of the PREOF concept.
>>
>>       A hierarchical relationship between OAM domains can be created
>>
>>       using the Level field value.
>>
>> And another update:
>>
>> OLD TEXT:
>>
>>       Session ID is a four-bits field.
>>
>> NEW TEXT:
>>
>>       Session ID - is a 4-bit field.  Session field is used to distinguish
>>
>>       OAM sessions originated from the same node (a given Maintenance
>>
>>       End Point may have multiple simultaneously active OAM sessions).
>>
>>
>>
>> 3. “Channel Type - contains the value of DetNet Associated Channel Type.”
>> This is confusing to me at first sight. It seem you are going to define a
>> new channel type. I struggled a while before I understand finally. So it
>> would be nice to revise the text.
>>
>> GIM>> I greatly appreciate your suggestions to clarify the definition of
>> the Channel Type field. Could you kindly propose the clarification making
>> it clearer?
>>
>> 4. You mentioned hybrid OAM a little bit in section 4. IMHO, it has
>> nothing to do with this draft, including the solution, the format. So, I
>> would suggest to clean up the hybrid OAM texts in this doc.
>>
>> GIM>> We've discussed and agreed with your suggestion. Removed the
>> section in the working version.
>>
>>
>>
>> Best,
>>
>> Tianran
>>
>>
>>
>> *From:* detnet [mailto:[e-mail]] *On Behalf Of *Janos
>> Farkas
>> *Sent:* Tuesday, October 11, 2022 10:23 PM
>> *To:* [e-mail]
>> *Subject:* [Detnet] WG Last Call: draft-ietf-detnet-mpls-oam-08
>>
>>
>>
>> All,
>>
>>
>>
>> This starts working group last call on
>>
>> https://datatracker.ietf.org/doc/draft-ietf-detnet-mpls-oam/
>>
>>
>>
>> The working group last call ends on October 25th.
>>
>> Please send your comments to the working group mailing list.
>>
>>
>>
>> No IPR has been disclosed against this document.
>>
>>
>>
>> Positive comments, e.g., "I've reviewed this document and believe it is
>> ready for publication", are welcome!
>>
>> This is useful and important, even from authors.
>>
>>
>>
>> Thank you,
>>
>> János (DetNet Co-Chair & doc Shepherd)
>>
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