Hi Rakesh,


From: Rakesh Gandhi <[email protected]>
Sent: Monday, September 14, 2026 3:16 PM
To: DECRAENE Bruno INNOV/NET <[email protected]>
Cc: [email protected]; SPRING WG <[email protected]>
Subject: Re: [spring] draft-ietf-spring-stamp-srpm-mpls

Hi Bruno,

Thank you for the review.

We have posted rev-07 that addresses your comments.

Thank you.
Works for me.

--Bruno

Please see replies inline with <RG>...


On Wed, Sep 2, 2026 at 10:07 AM 
<[email protected]<mailto:[email protected]>> wrote:
[speaking as individual contributor]

Hi authors,

As part of a discussion on the MPLS MNA defined in this draft, I had the 
opportunity to read section 7 again [1]

Please find below some comments/questions.


1.      Offset determination
§7.1
“When a Session-Reflector receives a test packet with the MNA Sub-Stack with 
opcode MNA.TSF, it timestamps the test packet payload at a fixed offset, pops 
the MNA Sub-Stack (after completing any other network actions), and forwards 
the test packet as defined in the loopback measurement mode for SR-MPLS paths 
in this document.”

§7.1.1
“The following properties are locally defined by the operator for this opcode.
· The timestamp format (e.g., 64-bit PTPv2 or NTPv4), to be added to the 
Session-Sender test packet payload.
· The offset in the Session-Sender test packet payload (e.g., STAMP test packet 
in Figure 5 of [RFC8762<https://www.rfc-editor.org/info/rfc8762>] with an 
offset of 16 bytes for Receive Timestamp).”

Since this fixed offset must be determined and configured by the network 
operator, could the document precisely define the starting field and the ending 
field defining this offset (presumably offset:= ending field – starting field).
Trying to guess, is this dependent on whether IPv4 or IPv6 is used for the test 
packet? Is this dependent on the number of MPLS labels added for the return 
path?
May be the §14.1 (OPS consideration for TSF) could refer to this and point to 
the relevant specification text.

<RG> Added as:


   The TSF opcode enables the Session-Reflector to write the 64-bit

   timestamp in the "Receive Timestamp" field [RFC8972], located at a

   begin offset of 16 bytes from the start of the STAMP test packet

   payload as shown in the Session-Reflector test packet in Figure 2 of

   Section 3 of [RFC8972].



2.      MNA.TSF value
“A value for the locally configured MPLS Network Action opcode MNA.TSF, called 
the TSF Network Action, is selected by the operator from the "Private Use 
Range: 115-126" [RFC9994<https://www.rfc-editor.org/info/rfc9994>] on the 
Session-Reflector node.”

Can you clarify why this specification opted for a Private value, rather than a 
standardized value?
From a network operator standpoint, this represents extra work, for no value 
that I could determine.

<RG> Ok, the draft is updated to use standardized values.
<RG> This was also the feedback from the MPLS WG chairs.





3.      Configuration
“The Session-Sender needs to know if the Session-Reflector is capable of 
processing the TSF Network Action to avoid dropping the test packets. This 
capability can be locally configured on the Session-Sender or signaled. 
Signaling extensions for this capability exchange are outside the scope of this 
document. »

My understanding is that the session sender needs to know other parameters. 
E.g., the MAN.TSF value, the offset, the timestamp format

<RG> The updated draft removes the configuration steps.

Thanks,
Rakesh (for authors)




Thank you,
--Bruno

[1] 
https://datatracker.ietf.org/doc/html/draft-ietf-spring-stamp-srpm-mpls-06#name-loopback-measurement-mode-w


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