Re: [RTG-DIR] Rtgdir early review of draft-ietf-mpls-inband-pm-encapsulation-08

[Weiqiang Cheng <[e-mail]>]

Hi Darren,
Thank you very much for your detailed review and comments.
We’ve addressed your feedback in the new Version -10, available at 
https://www.ietf.org/archive/id/draft-ietf-mpls-inband-pm-encapsulation-10.html 

For specific responses to your comments, please see my inline feedback marked as [Weiqiang].
Any comments are welcome.

Best Regards,
Weiqiang


Original
From: DarrenDukesviaDatatracker <[e-mail]>
To: [e-mail] <[e-mail]>;
Cc: [e-mail] <[e-mail]>;[e-mail] <[e-mail]>;
Date: 2024年02月24日 08:39
Subject: Rtgdir early review of draft-ietf-mpls-inband-pm-encapsulation-08
Reviewer: Darren Dukes
Review result: Has Issues

I've been assigned as part of the Routing Directorate to review
draft-ietf-mpls-inband-pm-encapsulation-08.txt. In reviewing the draft I note
it has issues that should be addressed.

Review
=========================
Section 2:
[minor] - line 234-239 says the TTL and TC SHOULD be that of the previous label
for the XL and FLI, but MAY be set to other values if they will not be exposed
as top of stack.  Is there any recommended value for XL and FLI if not that of
the preceding label, eg when they cannot appear at top of stack?
[Weiqiang] The text was borrowed from section 4.2 of RFC6790 and there are no recommended values.

[minor] - Section 2.1 lines 364-365 Is this an exhaustive list of possible
"application label" types? If not it's better to state that these are
non-exhaustive examples.
[Weiqiang] This is not an exhaustive list of possible types. The text was updated to reflect that.

[minor] - Section 3  This sentence does not make sense " If the hop-by-hop
measurement is applied, i.e., the T bit is set to 0, then whether the transit
node or the egress node is the processing node. "
[Weiqiang] This sentence was removed.

[minor] - Section 3 "egress node" is not defined so I cannot tell how an
"egress node" knows it's an "egress node" and takes the correction action in
bullet 2 of this section. A similar definition for "ingress node" is needed.
[Weiqiang] There is definition of MPLS ingress/egress node in RFC3031, so the reference to that RFC was added.

[major] - Section 3 I do not see any description of the protocol to the
external NMS. Is that described in another draft and does it need to be updated
for the content in this section?
[Weiqiang] There is description of the protocols to the external NMS in draft-ietf-ippm-alt-mark-deployment, so the reference to that draft was added.

[major] - Section 4 states "There are two ways of allocating Flow-ID" I find
this section a bit confusing.  The two ways appear to be two examples of how
flow-id may be assigned.  The only normative text in this section is the last
paragraph.  What happens if an implementation chooses another means of flow-ID
allocation that meets the  requirement in the last paragraph? Would it affect
interoperability? Would it be non-compliant? Are there more than two ways?
[Weiqiang] You're absolutely correct the two ways are non-exhaustive. As long as the requirement in the last paragraph is met, the interoperability can be met and it would be compliant.

[major] - Section 5 FRLD and FLC are needed along a path, but are they not
needed in the entire measurement domain along any possible path? If the network
reconverges and the PHP is no longer FLC I expect some strange behaviors are
possible.  Can you clarify this?
[Weiqiang] FRLD and FLC are needed along a path the performance measurement is applied to, if the network reconverges, then it's expected that the ingress node should stop adding FL until the ingress node confirms that FRLD and FLC are met along the new path.

[major] - Section 6 Can you expand on the ECMP problem with FLI specifically?
This section leaves me guessing if it's intended that some packets of a flow
contain an FLI and other do not, therefore forcing some packets of a flow on a
different path... but I've not understood that up until this section. With
these assumptions I don't see how the workarounds in the referenced
specification are applicable and it appears specific operation needs to be
specified for FLI.
[Weiqiang] Yes, section 6 has been expanded. Please check the text update.

[major] - Section 7 I see no text indicating how the multi-measurement-domain
FLI value can be solved at ingress, or transit. Is it solvable? Can a packet
traverse multiple measurement domains as its SR SID list may cross multiple
domains.
[Weiqiang] In the real deployment only one domain is involved, so some text was added to make multi-measurement-domain scenario out of scope.

[minor] - Section 7 What is the boundary of the measurement domain? Is the
measurement domain not the entire MPLS domain of an operator? Are there
recommendations for operators?
[Weiqiang] Some text was added to clarify the boundary of the measurement domain.

[nit] - Section 7 This sentence is ambiguous, can it be simplified like follows
( up to you) ... s/Improper configuration so that the Flow-ID label being
passed from one domain to another would likely result in potential Flow-ID
conflicts./Improper configuration so the Flow-ID label is passed from one
measurement domain to another would result in Flow-ID conflicts./
[Weiqiang] Thank you for the suggested text change, which was applied.