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

Dear Darren,
Thank you for your detailed review and comments. 
Co-authors will respond and address these comments promptly.
Best,
Weiqiang

From: Darren Dukes via Datatracker
Date: 2024-02-24 08:39
To: rtg-dir@ietf.org
CC: draft-ietf-mpls-inband-pm-encapsulation.all; mpls
Subject: [mpls] 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?

[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.

[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. "

[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.

[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?

[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?

[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?

[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.

[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.

[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?

[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./

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