[ippm] Éric Vyncke's Discuss on draft-ietf-ippm-ioam-flags-09: (with DISCUSS and COMMENT)

Éric Vyncke via Datatracker <noreply@ietf.org> Wed, 29 June 2022 05:42 UTC

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Subject: [ippm] Éric Vyncke's Discuss on draft-ietf-ippm-ioam-flags-09: (with DISCUSS and COMMENT)
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Éric Vyncke has entered the following ballot position for
draft-ietf-ippm-ioam-flags-09: Discuss

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# Éric Vyncke, INT AD, comments for draft-ietf-ippm-ioam-flags-09
CC @evyncke

Thank you for the work put into this document.

Please find below some blocking DISCUSS points (easy to address as it is about
clarifications), some non-blocking COMMENT points (but replies would be
appreciated even if only for my own education), and some nits.

Thanks to Pascal Thubert for his internet directorate review at:
(please consider Pascal's comments as mine).

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

I hope that this helps to improve the document,




As noted in https://www.ietf.org/blog/handling-iesg-ballot-positions/, a
DISCUSS ballot is a request to have a discussion on the following topics:

### Section 4.2 which address

`The address of the node performing the copy operation` is confusing in the
case of multiple interfaces (typical for a transit device BTW)... Which address
should be used ? If the packet was received through an interface with a global
address, then this should be the obvious choice or a loopback interface or ???

### Section 4.2 just truncation ?

   The copy is also truncated, i.e., any payload that
   resides after the IOAM option(s) is removed before transmitting the
   looped back packet back towards the encapsulating node.
It is unclear what happens to the IPv6 Next header field... Should the IP
header length field be modified ?

### Section 4.2 forwarding ?

It is unclear whether the packet is sent back to the source via the received
interface or whether the packet is forwarded based on the FIB.

### IANA considerations conflicting text ?
In section 4.1:
   An IOAM trace option that has the Loopback flag set MUST have the
   value '1' in the most significant bit of IOAM-Trace-Type, and '0' in
   the rest of the bits of IOAM-Trace-Type.
but in section 6:
   IANA is requested to allocate the following bits in the "IOAM Trace
   Flags Registry" as follows:

   Bit 1  "Loopback" (L-bit)

   Bit 2  "Active" (A-bit)

   Note that bit 0 is the most significant bit in the Flags Registry.

Is it bit 0 or bit 1 ?



### "loopback"

No need to reply, but every time I read "loopback", I think of the local
"loopback interface". The use of "echo" would probably have made my reading
easier ;-)

### Section 4.1

   An IOAM trace option that has the Loopback flag set MUST have the
   value '1' in the most significant bit of IOAM-Trace-Type, and '0' in
   the rest of the bits of IOAM-Trace-Type.
Does it prevent further enhancements to Trace types ?

### Section 4.1.1

"SHOULD NOT exceed 1/N of the interface capacity" but this recommendation is
only for the encapsulating node while there are nodes / links on the path that
may have much more constrained capacity. I suggest to remove this part and
replace it by text not refering to encapsulating node interface.

### Section 5

   IOAM options are encapsulated in one of the IOAM encapsulation types,
   e.g., [I-D.ietf-sfc-ioam-nsh], or [I-D.ietf-ippm-ioam-ipv6-options].
Should this text also appear in the section 4?

### Section 5 capacity

   Thus, the rate of the traffic that
   includes the Active flag rate SHOULD NOT exceed 1/N of the interface
   capacity on any of the IOAM node's interfaces.
Should thie be "IOAM nodes' interfaces" to take into account all IOAM nodes
(including transit).


### Section 5
s/This draft focuses on three possible use cases/This document focuses on three
possible use cases/

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues.

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments