Operations, Administration, and Maintenance (OAM) for Deterministic Networks (DetNet) with IP Data Plane
draft-ietf-detnet-ip-oam-13

# Internet AD comments for draft-ietf-detnet-ip-oam-12
CC @ekline

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## Comments

### S3.3, S3.4

* Do the same comments apply to DetNet-style MPLS encap'd over IP or GRE
  directly, i.e. without UDP as described in RFC 4023?

  Maybe nobody runs that, so I'm genuinely curious.

Thanks for this document. I have some mostly minor comments below, that I hope may be helpful. Also, thanks to Roman for being special guest AD, and to János for the clear and helpful shepherd write-up.

### Section 2.1, unused

Defined, never used:

- DiffServ (but I notice 'DSCP' is used without expansion in Section 3)
- PREF (except it's used by a later definition)
- POF
- RDI

I think all these could be removed (folding PREF into the 'Detnet Node' definition where it's used).

Defined, only used once:

- ACH is used in Figure 1, and you provide a definition in-line, which is sufficient, so I think this could be removed from §2.1.
- Underlay network, in this case, the definition seems useful since it keeps the paragraph in §3 more concise.

### Section 3, this sentence no verb

It took me longer than I would care to admit to work out that what's missing in this sentence is the verb "to be":

"The DetNet data plane encapsulation in a transport network with IP encapsulations specified in Section 6 of [RFC8939]."

I.e. it needs an "is" before "specified".

### Section 3, "e.g." or "i.e."

In the below-quoted sentence, do you really mean "e.g."? That is, are you stating an example? It doesn't look that way to me, it looks as though you mean "in other words", not "for example" which is what "e.g." means. If you mean "in other words", what you want is "i.e.", or just write out "in other words" for the avoidance of all uncertainty.

"In order to use ICMP for these purposes with DetNet, DetNet nodes must be able to associate ICMP traffic between DetNet nodes with IP DetNet traffic, e.g., ensure that such ICMP traffic uses the DetNet IP data plane in each node, otherwise ICMP may be unable to detect and localize failures that are specific to the DetNet IP data plane."

### Section 3.1, co-routing via UDP source port

I'm mulling over "may be able to achieve co-routedness of OAM with the monitored IP DetNet flow in multipath environments, e.g., Link Aggregation Group or Equal Cost Multipath, via use of a UDP source port value that results in the OAM traffic and the monitored IP DetNet flow hashing to the same path based on the packet header hashes used for path selection". 

I guess this is true, but the word "may" is doing a lot of work here. The counter-case is when the hash function isn't uniform among all forwarders in the network. In such cases, it might not be possible to use this technique to co-route the OAM with a monitored flow.

I guess this might just be a case of ¯\_(ツ)_/¯ though -- your document is saying "you have to have co-routing to get good OAM"... if the network isn't able to provide co-routed paths, then oh well, we can't have good OAM, perhaps it means we need to rearchitect the network?

If you agree, is it worth saying a few words to that effect (maybe without the shrug emoji) in this section?

### Section 4, wrong xref

"Interworking between DetNet domains with IP and MPLS data planes analyzed in Section 6.2 of [I-D.ietf-detnet-mpls-oam]."

There is no Section 6.2 of draft-ietf-detnet-mpls-oam-15. Section 6 is Security Considerations. Probably you mean Section 4.2?

### Section 7

You have "TBA" as the whole body of this section. I guess it's time to either put something there or delete the section. :-)

Thanks for addressing the TSVART review, thanks to Bernard Aboba for the review.

# Éric Vyncke, INT AD, comments for draft-ietf-detnet-ip-oam-12

Thank you for the work put into this document.

Please find below some non-blocking COMMENT points (but replies would be appreciated even if only for my own education), and one nit.

Special thanks to János Farkas for the shepherd's detailed write-up including the WG consensus and the justification of the intended status.

Other thanks to Roman Danyliw as the acting AD ;-)

I hope that this review helps to improve the document,

Regards,

-éric

# COMMENTS (non-blocking)

## Section 1

Is the 1st paragraph defining what is OAM a little too light ? Operations cover more than performance monitoring. But, this is not critical for this I-D.

## Section 2.1

Should there be a reference for diff serv and ICMPv[46]?

Isn't it a little weird to use in an IP-only document the sentence `MPLS networks providing LSP connectivity between DetNet nodes are an example of the underlay layer` ?

## Section 3

I will let my fellow OPS ADs to chime in, but `OAM protocols and mechanisms act within the data plane of the particular networking layer` is of course applicable for the in-path monitoring part of OAM, but probably not for the control part of OAM, e.g., netconf can be in a separate plane.

What about the use of IPv6 flow label ? Would it help for the IPv6 flows ?

## Section 3.1

While I am far from being a "flow hash" expert, is it really possible for compute UDP ports having the same hash value ? Especially when most vendors do not make their flow hash algorithms public ?

To be honest, the intent of sections 3.1 to 3.4 are unclear to me, hence my above question.

## Section 7

I was really about to raise a DISCUSS for this, but it is too trivial to fix: please either remove this section or add some contents.

# NITS (non-blocking / cosmetic)

## Oxford comma ?

Should there be an Oxford comma in `Administration and Maintenance`? Notably in the title and other places.

Thanks to Bernard Adoba for the TSVART review.

This document seems to be a very long version of the sentence "make sure your OAM flows hash the same as your data flows", but I see no transport issues.

Hi,

Thanks for this document.  Just a few minor comments.

Minor level comments:

(1) p 5, sec 3.4.  Active OAM Using GRE-in-UDP Encapsulation

   [RFC8086] has defined the method of encapsulating GRE (Generic
   Routing Encapsulation) headers in UDP.  GRE-in-UDP encapsulation can
   be used for IP DetNet OAM as it eases the task of mapping an OAM test
   session to a particular IP DetNet flow that is identified by N-tuple.
   Matching a GRE-in-UDP tunnel to the monitored IP DetNet flow enables
   the use of Y.1731/G.8013 [ITU-T.1731] as a comprehensive toolset of
   OAM.  The Protocol Type field in GRE header must be set to 0x8902
   assigned by IANA to IEEE 802.1ag Connectivity Fault Management (CFM)
   Protocol / ITU-T Recommendation Y.1731.  Y.1731/G.8013 supports
   necessary for IP DetNet OAM functions, i.e., continuity check, one-
   way packet loss and packet delay measurement.

A few minor comments on this paragraph:

1. The section title is about "Active OAM Using GRE-in-UDP Encapsulation" but the text seems to be more specifically referring to Y.1731.  Should the title of the section be refined?

2. Perhaps "set to 0x8902 assigned" => "set to 0x8902, assigned"

3. The last sentence of the paragraph doesn't scan properly.


(2) p 6, sec 7.  Acknowledgment

   TBA

Just a note that this is still blank, and you may want to remove this section if you don't wish to acknowledge anyone.

Regards,
Rob