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Stenn 3 Internet-Draft Network Time Foundation 4 Intended status: Standards Track March 14, 2016 5 Expires: September 15, 2016 7 Network Time Protocol Last Extension Field 8 draft-stenn-ntp-last-extension-00 10 Abstract 12 NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions 13 of the NTP Protocol have supported symmetric private key MAC 14 authentication. MACs pre-date the Extension Fields introduced in RFC 15 5905 [RFC5905], and as the number of Extension Fields grows there is 16 an increasing chance of ambiguity when deciding if the "next" set of 17 data is an Extension Field or a MAC. This proposal defines a new 18 Extension Field which is used to signifiy that it is the last 19 Extension Field in the packet. If present, any subsequent data 20 SHOULD be considered to be a legacy MAC. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 15, 2016. 39 Copyright Notice 41 Copyright (c) 2016 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2 58 2. The Last Extension Field Extension Field . . . . . . . . . . 2 59 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3 60 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 61 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 62 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 65 1. Introduction 67 NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions 68 of the NTP Protocol have supported symmetric private key MAC 69 authentication. MACs pre-date the Extension Fields introduced in RFC 70 5905 [RFC5905], and as the number of Extension Fields grows there is 71 an increasing chance of ambiguity when deciding if the "next" set of 72 data is an Extension Field or a MAC. This proposal defines a new 73 Extension Field which is used to signifiy that it is the last 74 Extension Field in the packet. If present, any subsequent data 75 SHOULD be considered to be a legacy MAC. 77 1.1. Requirements Language 79 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 80 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 81 document are to be interpreted as described in RFC 2119 [RFC2119]. 83 2. The Last Extension Field Extension Field 85 Now that multiple extension fields are a possibility, and the chance 86 that additional packet data could be an Extension Field or an old- 87 style MAC, having a means to indicate that there are no more 88 Extension Fields in an NTP packet, and any subsequent data MUST be 89 something else, almost certainly an old-style MAC, is a valuable 90 facility. 92 0 1 2 3 93 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 94 +---------------+---------------+-------------------------------+ 95 | Field Type | Field Length | 96 +-------------------------------+-------------------------------+ 98 NTP Extension Field: Last Extension Field 100 Field Type: TBD (Recommendation for IANA: 0x2008 (Last Extension 101 Field, MAC OPTIONAL)) 103 Field Length: 4 105 Payload: None. 107 Example: 109 0 1 2 3 110 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 111 +---------------+---------------+-------------------------------+ 112 | Field Type (0x2008) | Field Length (0x0004) | 113 +-------------------------------+-------------------------------+ 114 | MAC Key ID | 115 +-------------------------------+-------------------------------+ 116 | Sixteen | 117 +-------------------------------+-------------------------------+ 118 | Octets | 119 +-------------------------------+-------------------------------+ 120 | of | 121 +-------------------------------+-------------------------------+ 122 | MAC | 123 +-------------------------------+-------------------------------+ 125 Example: NTP Extension Field: Last Extension Field 127 3. Acknowledgements 129 The author wishes to acknowledge the contributions of Joey 130 Saccadonuts. 132 4. IANA Considerations 134 This memo requests IANA to allocate NTP Extension Field Types 0x0007 135 (I-Do), 0x2007 (I-Do, MAC OPTIONAL), 0x4007 (I-Do Response), and 136 0x6007 (I-Do Response, MAC OPTIONAL) for this proposal. 138 5. Security Considerations 140 Additional information TBD 142 6. Normative References 144 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 145 Requirement Levels", BCP 14, RFC 2119, 146 DOI 10.17487/RFC2119, March 1997, 147 . 149 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 150 "Network Time Protocol Version 4: Protocol and Algorithms 151 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 152 . 154 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 155 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 156 October 2014, . 158 Author's Address 160 Harlan Stenn 161 Network Time Foundation 162 P.O. Box 918 163 Talent, OR 97540 164 US 166 Email: stenn@nwtime.org