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Network Time Protocol MAC/Last Extension Fields

Document Type Expired Internet-Draft (candidate for ntp WG)
Expired & archived
Authors Harlan Stenn , Danny Mayer
Last updated 2019-09-26 (Latest revision 2019-03-25)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Additional resources Mailing list discussion
Stream WG state Call For Adoption By WG Issued
Document shepherd (None)
IESG IESG state Expired
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


NTP packets can be authenticated by a Message Authentication Code (MAC) if a MAC is present at the end of an NTP packet. The legacy format for this MAC is not formatted as an NTP Extension Field, and its presence may cause some implementations a parsing ambiguity. This proposal introduces two ways to resolve this problem. One is to provide a MAC Extension Field. The other is an extension field that unambiguously declares itself to be the last extension field in an NTP packet (so any additional data MUST be a legacy MAC). RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH BEFORE PUBLISHING: The source code and issues list for this draft can be found in


Harlan Stenn
Danny Mayer

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)