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A Secure Selection and Filtering Mechanism for the Network Time Protocol Version 4

Document Type Replaced Internet-Draft (ntp WG)
Expired & archived
Authors Neta Rozen Schiff , Danny Dolev , Tal Mizrahi , Michael Schapira
Last updated 2019-11-05 (Latest revision 2019-09-03)
Replaced by draft-ietf-ntp-chronos
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
Additional resources Mailing list discussion
Stream WG state Adopted by a WG
Document shepherd (None)
IESG IESG state Replaced by draft-ietf-ntp-chronos
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This Internet-Draft is no longer active.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:


The Network Time Protocol version 4 (NTPv4) defines the peer process, the clock filter algorithm, the system process and the clock description algorithm. The clock filter algorithm and the system process, as defined in RFC 5905, are the mechanism according to which an NTP client chooses the NTP servers it synchronized with. This document specifies an alternative set of client mechanisms, named Chronos, that is backward compatible with NTPv4, and offers an improved level of security against time shifting attacks.


Neta Rozen Schiff
Danny Dolev
Tal Mizrahi
Michael Schapira

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