Hi, Andy,

Thank you for this! 

Benoit (as shepherd),

This was my conclusion as well, as author of 5085:
> RFC 5085 doesn't make any reference to QoS treatment as a part of path 
> congruence […]
> the text in the draft to be an accurate quote, except that I wouldn't refer 
> to only section 6. I


And this is what I also asked Greg some emails ago, twice;
> then I would ask Greg to write an alternative example of in-band OAM in prior 
> IETF work that includes QoS treatment to ensure path congruence to include in 
> the draft

Thanks!

Carlos.

> On Jun 4, 2025, at 7:48 AM, Andrew G. Malis <[email protected]> wrote:
> 
> Hi Med, Carlos, Greg, et al!
> 
> RFC 5085 doesn't make any reference to QoS treatment as a part of path 
> congruence. It only relies on label equivalence for MPLS PWs and the L2TPv3 
> session for IP PWs to provide in-band VCCV.
> 
> Greg does have a point that QoS/traffic class packet forwarding treatment can 
> have an effect on in-band QoS, and I see that is discussed in the 
> characterization draft, but it wasn't included in 5085 as written.
> 
> So I find the text in the draft to be an accurate quote, except that I 
> wouldn't refer to only section 6. I would either refer to the RFC as a whole, 
> or if you do want section references, I would include sections 3 and 5.1.1 in 
> addition to section 6.
> 
> However, Greg's comment may not be just about the accuracy of the quote, but 
> not including QoS treatment to ensure path congruence as a part of the 
> definition of in-band OAM.
> 
> So if my interpretation of Greg's comment is correct, then I would ask Greg 
> to write an alternative example of in-band OAM in prior IETF work that 
> includes QoS treatment to ensure path congruence to include in the draft.
> 
> Cheers,
> Andy
> 
> 
> On Wed, Jun 4, 2025 at 4:48 AM <[email protected] 
> <mailto:[email protected]>> wrote:
>> Hi Andy/Stewart/Matthew,
>> 
>>  
>> 
>> I hope you are doing well.
>> 
>>  
>> 
>> I’m soliciting your feedback on this text which is included in  
>> draft-ietf-opsawg-oam-characterization:
>> 
>>  
>> 
>>       An example of "Path-Congruent OAM" is the Virtual Circuit
>> 
>>      Connectivity Verification (VCCV), described is Section 6 of
>> 
>>       [RFC5085] as "The VCCV message travels in-band with the Session
>> 
>>       and follows the exact same path as the user data for the session".
>> 
>>       Thus, the term "in-band" in [RFC5085] refers to using the same
>> 
>>       path as the user data.  This term is also used in Section 2 of
>> 
>>       [RFC6669] with the same meaning, and the word "congruent" is
>> 
>>       mentioned as synonymous.
>> 
>>  
>> 
>> Do you see any disconnect between this text and RFC5085?
>> 
>>  
>> 
>> FWIW, draft-ietf-opsawg-oam-characterization defines “Path-Congruent OAM” as 
>> follows:
>> 
>>  
>> 
>>          The OAM information follows the exact same path as the observed
>> 
>>          data traffic.  This was sometimes referred to as "in-band".
>> 
>>  
>> 
>> Thank you.
>> 
>>  
>> 
>> Cheers,
>> 
>> Med
>> 
>>  
>> 
>> PS: Please see below for more context.
>> 
>>  
>> 
>> De : Greg Mirsky <[email protected] <mailto:[email protected]>> 
>> Envoyé : mercredi 4 juin 2025 07:32
>> À : Carlos Pignataro <[email protected] <mailto:[email protected]>>
>> Cc : Ops Area WG <[email protected] <mailto:[email protected]>>
>> Objet : [OPSAWG]Re: WG LAST CALL: Guidelines for Charactering "OAM"
>> 
>>  
>> 
>> Hi Carlos,
>> 
>> please find my notes below tagged GIM2>>.
>> 
>>  
>> 
>> Regards,
>> 
>> Greg
>> 
>>  
>> 
>> On Tue, Jun 3, 2025 at 1:21 AM Carlos Pignataro <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> Greg:
>> 
>>  
>> 
>> While I’ll defer to Tal for a detailed response, I’ve provided three key 
>> points inline. 
>> 
>> See “CMP:” below
>> 
>>  
>> 
>> On Jun 1, 2025, at 7:49 PM, Greg Mirsky <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>>  
>> 
>> Hi Tal,
>> 
>> thank you for explaining updates. Please find my follow-up notes below 
>> tagged GIM>>.
>> 
>>  
>> 
>> Regards,
>> 
>> Greg
>> 
>>  
>> 
>> On Thu, May 29, 2025 at 5:59 PM Tal Mizrahi <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> Hi Greg,
>> 
>> Thanks again for reviewing the draft. Your comments for the previous
>> versions have helped in improving the draft.
>> Please see my responses to the latest comments that you have sent to
>> the authors off-list when you kindly reviewed an intermediate version
>> of the draft.
>> 
>> 
>> On Tue, May 13, 2025 at 8:38 PM Greg Mirsky <[email protected] 
>> <mailto:[email protected]>> wrote:
>> >
>> > Hi Tal,
>> >
>> > Thank you for your work on addressing my comments. I reviewed the working 
>> > version of the draft and have some comments and questions, which are below.
>> > Section 2:
>> >
>> > It is noted that "A frequently encountered case is the use of "in-band" to 
>> > mean either in-packet or on-path." If that is the case, and there are many 
>> > IETF documents that use these interpretations of "in-band," it seems like 
>> > it would be easy to provide several references in support of that 
>> > assumption.
>> 
>> [TM] Following your comment we have focused the following two paragraphs.
>> The following paragraph demonstrates the use of the term "in-band" in
>> the context of path-congruent OAM:
>> 
>>       Connectivity Verification (VCCV), described is Section 6 of
>>       [RFC5085] as "The VCCV message travels in-band with the Session
>>       and follows the exact same path as the user data for the session".
>>       Thus, the term "in-band" in [RFC5085] refers to using the same
>>       path as the user data.  This term is also used in Section 2 of
>>       [RFC6669] with the same meaning, and the word "congruent" is
>>       mentioned as synonymous.
>> 
>> GIM>> I don't think that your interpretation of "in-band" in RFC 5085 is 
>> accurate. The VCCV message not only traverses the same path as a data packet 
>> because the same labels are applied along the path, but it also receives the 
>> same forwarding treatment by the network because the same Traffic Class is 
>> used for the VCCV message as for the data packet. Thus, it is in-band with 
>> the monitored data flow, and topological equivalence is only one element, 
>> while it must be complemented by the QoS equivalence.
>> 
>>  
>> 
>> CMP: As an author of RFC 5085, I can confirm that you are completely wrong 
>> on this.
>> 
>> GIM2>> That is your personal opinion, not the opinion of other authors, and 
>> even less the opinion of PWE3 (later PALS) WG. As the PALS WG is winding 
>> down, the MPLS WG may be the community to provide a more authoritative 
>> interpretation of RFC 5085.
>> 
>>  
>> 
>> CMP: That said, you do not need to be an author to know this, you can 
>> actually **read** the RFC, where it says:
>> 
>> CMP: "in-band (i.e., following the same data-plane faith as PW data).”
>> 
>> CMP: “ travels in-band with the Session and follows the exact same path as 
>> the user data for the session"
>> 
>> CMP: Let’s not make up ‘interpretations’.
>> 
>>  
>> 
>>  
>> 
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