Network Time Protocol
MAC/Last Extension Fields
draft-stenn-ntp-mac-last-ef-02
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Internet Engineering Task Force H. Stenn
Internet-Draft D. Mayer
Intended status: Standards Track Network Time Foundation
Expires: August 25, 2018 February 21, 2018
Network Time Protocol MAC/Last Extension Fields
draft-stenn-ntp-mac-last-ef-02
Abstract
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 25, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
Stenn & Mayer Expires August 25, 2018 [Page 1]
Internet-Draft NTP MAC/Last Extension Fields February 2018
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. The Last Extension Field Extension Field - LAST-EF . . . . . 3
3. MAC Extension Field . . . . . . . . . . . . . . . . . . . . . 4
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
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, or if you
prefer, any subsequent data MUST NOT be considered to be an EF. 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.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Stenn & Mayer Expires August 25, 2018 [Page 2]
Internet-Draft NTP MAC/Last Extension Fields February 2018
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