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Internet Engineering Task Force H. Stenn
Internet-Draft Network Time Foundation
Intended status: Standards Track March 14, 2016
Expires: September 15, 2016


Network Time Protocol Last Extension Field
draft-stenn-ntp-last-extension-00

Abstract

NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions
of the NTP Protocol have supported symmetric private key MAC
authentication. MACs pre-date the Extension Fields introduced in RFC
5905 [RFC5905], and as the number of Extension Fields grows there is
an increasing chance of ambiguity when deciding if the "next" set of
data is an Extension Field or a MAC. This proposal defines a new
Extension Field which is used to signifiy that it is the last
Extension Field in the packet. If present, any subsequent data
SHOULD be considered to be a legacy MAC.

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 http://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 September 15, 2016.

Copyright Notice

Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect



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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. The Last Extension Field Extension Field . . . . . . . . . . 2
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4

1. Introduction

NTPv4 is defined by RFC 5905 [RFC5905], and it and earlier versions
of the NTP Protocol have supported symmetric private key MAC
authentication. MACs pre-date the Extension Fields introduced in RFC
5905 [RFC5905], and as the number of Extension Fields grows there is
an increasing chance of ambiguity when deciding if the "next" set of
data is an Extension Field or a MAC. This proposal defines a new
Extension Field which is used to signifiy that it is the last
Extension Field in the packet. If present, any subsequent data
SHOULD be considered to be a legacy MAC.

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].

2. The Last Extension Field Extension Field

Now that multiple extension fields are a possibility, and the chance
that additional packet data could be an Extension Field or an old-
style MAC, having a means to indicate that there are no more
Extension Fields in an NTP packet, and any subsequent data MUST be
something else, almost certainly an old-style MAC, is a valuable
facility.









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0 1 2 3
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
+---------------+---------------+-------------------------------+
| Field Type | Field Length |
+-------------------------------+-------------------------------+

NTP Extension Field: Last Extension Field

Field Type: TBD (Recommendation for IANA: 0x2008 (Last Extension
Field, MAC OPTIONAL))

Field Length: 4

Payload: None.

Example:

0 1 2 3
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
+---------------+---------------+-------------------------------+
| Field Type (0x2008) | Field Length (0x0004) |
+-------------------------------+-------------------------------+
| MAC Key ID |
+-------------------------------+-------------------------------+
| Sixteen |
+-------------------------------+-------------------------------+
| Octets |
+-------------------------------+-------------------------------+
| of |
+-------------------------------+-------------------------------+
| MAC |
+-------------------------------+-------------------------------+

Example: NTP Extension Field: Last Extension Field

3. Acknowledgements

The author wishes to acknowledge the contributions of Joey
Saccadonuts.

4. IANA Considerations

This memo requests IANA to allocate NTP Extension Field Types 0x0007
(I-Do), 0x2007 (I-Do, MAC OPTIONAL), 0x4007 (I-Do Response), and
0x6007 (I-Do Response, MAC OPTIONAL) for this proposal.






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5. Security Considerations

Additional information TBD

6. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.

[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
.

[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, .

Author's Address

Harlan Stenn
Network Time Foundation
P.O. Box 918
Talent, OR 97540
US

Email: stenn@nwtime.org






















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