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Network Time Protocol Version 4: Port Randomization

Approval announcement
Draft of message to be sent after approval:


From: The IESG <>
To: IETF-Announce <>
Cc: The IESG <>,,,,,,
Subject: Protocol Action: 'Port Randomization in the Network Time Protocol Version 4' to Proposed Standard (draft-ietf-ntp-port-randomization-08.txt)

The IESG has approved the following document:
- 'Port Randomization in the Network Time Protocol Version 4'
  (draft-ietf-ntp-port-randomization-08.txt) as Proposed Standard

This document is the product of the Network Time Protocol Working Group.

The IESG contact persons are Erik Kline and √Čric Vyncke.

A URL of this Internet Draft is:

Ballot Text

Technical Summary

   The Network Time Protocol can operate in several modes.  Some of
   these modes are based on the receipt of unsolicited packets, and
   therefore require the use of a well-known port as the local port
   number.  However, in the case of NTP modes where the use of a well-
   known port is not required, employing such well-known port
   unnecessarily increases the ability of attackers to perform blind/
   off-path attacks.  This document formally updates RFC5905,
   recommending the use of transport-protocol ephemeral port
   randomization for those modes where use of the NTP well-known port is
   not required.

Working Group Summary

   There was nothing particularly noteworthy in the WG process. 

Document Quality

   Many/most implementations already exhibit this behaviour.  More
   implementation text is in Section 5.


   Karen O'Donoghue is the Document Shepherd.
   Erik Kline is the Responsible Area Director.

RFC Editor Note