Re: [RTG-DIR] Rtgdir review of draft-ietf-sfc-ioam-nsh-10

[Mach Chen <[e-mail]>]

Hi Frank,

Please my responses inline...

> -----Original Message-----
> From: Frank Brockners (fbrockne) <[e-mail]>
> Sent: Monday, September 12, 2022 4:06 AM
> To: Mach Chen <[e-mail]>; [e-mail]
> Cc: [e-mail]; [e-mail]
> Subject: RE: Rtgdir review of draft-ietf-sfc-ioam-nsh-10
> 
> Hi Mach,
> 
> Thanks a lot for your detailed review - and sorry for the delay. Please see inline.
> 
> > -----Original Message-----
> > From: Mach Chen <[e-mail]>
> > Sent: Saturday, 27 August 2022 11:16
> > To: [e-mail]
> > Cc: [e-mail]; [e-mail]
> > Subject: Rtgdir review of draft-ietf-sfc-ioam-nsh-10
> >
> > Hello,
> > I have been selected as the Routing Directorate reviewer for this
> > draft. The Routing Directorate seeks to review all routing or
> > routing-related drafts as they pass through IETF last call and IESG review, and
> sometimes on special request.
> > The purpose of the review is to provide assistance to the Routing ADs.
> > For more information about the Routing Directorate, please see
> > http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir
> > Although these comments are primarily for the use of the Routing ADs,
> > it would be helpful if you could consider them along with any other
> > IETF Last Call comments that you receive, and strive to resolve them
> > through discussion or by updating the draft.
> >
> > Document: draft-ietf-sfc-ioam-nsh-10
> > Reviewer: Mach Chen
> > Review Date: 2022-08-22
> > IETF LC End Date:
> > Intended Status: Standards Track
> >
> > Summary:
> > I have some minor concerns about this document that I think should be
> > resolved before publication.
> >
> > Comments:
> > The draft is well written and easy to read.
> >
> > Section 3,
> > "The O-bit MUST be handled following the rules in [I-D.ietf-sfc-oam-packet]."
> >
> > According to [I-D.ietf-sfc-oam-packet], a NSH-encapsulated packet with
> > IOAM will not be considered as OAM packet. Thus, it's better to state
> > that "the O-bit MUST NOT be set" for packet with IOAM header in this
> document.
> 
> ...FB: I'm not sure that [I-D.ietf-sfc-oam-packet] states that a NSH-encapsulated
> packet with IOAM will not be considered as OAM packet, at least I did not find
> a reference. Do you have a pointer?
> There have been a lot of discussions on the O-bit in NSH including the use with
> IOAM. After careful consideration, it was decided to refer to
> [I-D.ietf-sfc-oam-packet] for the handling of the O-bit, rather than re-state
> things in draft-ietf-sfc-ioam-nsh. The reason for that is, that one needs to
> consider a variety of cases, including cases, where an operator would decide to
> add IOAM information to an NSH OAM packet, in which case the O-bit would
> be set according to draft-ietf-sfc-oam-packet.

As discussed with Greg, draft-ietf-ippm-ioam-flags defines an Active flag that might create Active OAM packet, in that case the "O" bit will be set. And I agree with Greg it's better to keep the quoted text as-is. Therefore, please ignore this comment.

> 
> >
> > Major Issues:
> > No major issues found.
> >
> > Minor Issues:
> > Quoted from Section 2.2, last paragraph of RFC 8300, it says:
> > "...Packets with Next Protocol values not supported SHOULD be silently
> dropped
> >       by default, although an implementation MAY provide a configuration
> >       parameter to forward them."
> >
> > With above requirement, when insert an IOAM header to a
> > NSH-encapsulated packet, the encapsulating node MUST make sure that
> > every nodes (e.g., SFF, SF) along the service path supports IOAM,
> > otherwise, the packet will be silently dropped. IMHO, this should be
> > discussed in the document to make this more explicit.
> 
> ...FB: Good point. If we follow the approach of RFC8300, wouldn't it make
> sense to also use SHOULD here? I.e., the operator SHOULD ensure that all
> nodes along the service path support IOAM. Otherwise packets with IOAM are
> likely to be dropped per [RFC 8300].

I fine with using "MUST" or "SHOULD”, and your example text looks good to me. 

> 
> Thanks again, Frank

You are welcome!

Best regards,
Mach
> 
> >
> > Nits:
> > None.
> >
> > Best regards,
> > Mach