IETF Last Call Review of draft-ietf-ntp-over-ptp-05
review-ietf-ntp-over-ptp-05-tsvart-lc-perkins-2025-09-21-00

This document has been reviewed as part of the transport area review team's
ongoing effort to review key IETF documents. These comments were written
primarily for the transport area directors, but are copied to the document's
authors and WG to allow them to address any issues raised and also to the IETF
discussion list for information.

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The draft outlines what is PTP and describes some of the limitations of
PTP-capable hardware and how these interact with implementations that try to
use that hardware to support NTP. It describes a new transport for NTP within
PTP packets, allowing NTP to make use of hardware that only timestamps PTP, and
extends NTP to make use of the timing information provided by PTP.

The draft is clearly written and generally well explained. From a transport
perspective it appears to be ready, excepting a minor nit noted below.

The PTP transport for NTP is sent within existing PTP messages. This generates
packets containing a new PTP TLV, that presumably has some potential to disrupt
the operation of non-upgraded PTP implementations, but otherwise appears to
match usual NTP behaviour and to fit within PTP, and introduces no new
transport issues.

The Network Correction Extension Field similarly does not appear to have any
novel transport implications.

The Security Considerations notes that “The PTP transport prevents NTP clients
from randomizing their source port”. It would be helpful it is also included a
brief statement of why this might be an issue and a reference for where to find
further information (presumably RFC 9109).

Regards,
Colin