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Network Time Protocol MAC/Last Extension Fields

The information below is for an old version of the document.
Document Type This is an older version of an Internet-Draft whose latest revision is Expired
Authors Harlan Stenn , Danny Mayer
Last updated 2018-08-26 (Latest revision 2018-02-22)
Stream (None)
Expired & archived
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft is available in these formats:


NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions of the NTP Protocol have supported symmetric private key Message Authentication Code (MAC) authentication. MACs were first described in Appendix C of RFC 1305 [RFC1305] and are further described in RFC 5905 [RFC5905]. As the number of Extension Fields grows there is an increasing chance of a parsing ambiguity when deciding if the "next" set of data is an Extension Field or a legacy MAC. This proposal defines two new Extension Fields which may be used to avoid this ambiguity. One, LAST-EF, is used to signify that it is the last Extension Field in the packet. If the LAST-EF is present, any subsequent data MUST be considered to be a legacy MAC. The other, MAC-EF, allows one or more MACs to be encapsulated in an Extension Field. If all parties in an association support MAC-EF, the use of a legacy MAC may be avoided.


Harlan Stenn
Danny Mayer

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