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Internet Engineering Task Force                                 H. Stenn
Internet-Draft                                   Network Time Foundation
Intended status: Standards Track                          March 25, 2019
Expires: September 26, 2019


       Network Time Protocol Extended Information Extension Field
                draft-stenn-ntp-extended-information-04

Abstract

   RFC EDITOR: PLEASE REMOVE THE FOLLOWING PARAGRAPH BEFORE PUBLISHING:

   The source code and issues list for this draft can be found in
   https://github.com/hstenn/ietf-ntp-extended-information-ef

   The core network packet used by NTP has no spare bits available for
   reporting additional state information and no larger data areas
   available for larger amounts of information.  This proposal offers a
   new extension field that would contain this additional information.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 26, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (https://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 Extended Information Extension Field  . . . . . . . . . .   2
     2.1.  Version 0 Content Descriptor and Content Data fields  . .   3
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The core NTP packet format has changed little since RFC 958 [RFC0958]
   was published in 1985.  Since then, there has been demonstrated need
   to convey additional information about NTP's state in an NTP packet
   but no backward-compatible way to usurp the few otherwise potentially
   available bits has been found, and no larger data areas are available
   in the core packet structure.  This proposal offers a new extension
   field that would contain this additional information.

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 Extended Information Extension Field

   The Field Type of the Extended Information EF includes a version
   number field in the low-order bits of the first octet, to make it
   easier to evolve this specification.  The initial specification for
   this proposal uses Version 0, which equates to 0x0009 [ADJUST AS
   NEEDED BASED ON IANA, IF AN IANA REGISTRY IS USED].  A future
   revision for Version 1 would use 0x0109 [IBID].

   The payload for Version 0 is comprised of a two octet Content
   Descriptor followed by a two octet Content Data field, as described
   below.






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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           |
   +-------------------------------+-------------------------------+
   |     Content Descriptor 1      |       Content Data 1          |
   +---------------------------------------------------------------+

                 NTP Extension Field: Extended Information

   Field Type: TBD (Recommendation for IANA: 0x0009 (Extended-
   Information, Version 0))

   Field Length: as needed

2.1.  Version 0 Content Descriptor and Content Data fields

   There are 16 bits available for state information in the Version 0
   Extended Information Content Descriptor.  These bits are allocated as
   follows:

   0x0001:  TAI Offset is stored in the low-order 8 bits (the second
      octet) of the Content Data.

   0x0002:  Interleave Mode indicator in the low order bit of the first
      octet of the Content Data.  [NOTE: this may not be useful, and it
      can be removed if desired.  It can serve as a belt-and-suspenders
      way to identify when a packet contains interleaved timestamps.]

   0xFFFD:  Reserved for future versions.  SHOULD be zeroes for Version
      0, and the meaning of any nonzero values is unspecified.

   The Content Data field of the Version 0 Extended Information
   extension field is comprised of two octets, with the contents
   allocated as follows:

   0xXXNN:  The low-order 8 bits (NNNN) are the TAI Offset.  Any data in
      the high-order 8 bits (XXXX) are not part of the TAI Offset.

   0xX0XX:  A value of 0 in the low-order bit of the first octet
      indicates that the timestamps in the base packet are not
      interleave-mode timestamps.

   0xX1XX:  A value of 1 in the low-order bit of the first octet
      indicates that the timestamps in the base packet are interleave-
      mode timestamps.

   0xN2XX:  thru



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   0xNDXX:  Any of the seven high-order bits in the first octet are
      reserved for future versions and SHOULD be zero for Version 0.
      The meaning of any nonzero values is unspecified.

    Content Descriptor 1     Content Data 1
            0x0001         TAI offset in the low-order 8 bits, 24-31
            0x0002         Interleave Mode indicator in Bit 23
            0xFFFD         Reserved (Zeroes)

    Interleave Mode: 1 if the sender is in interleave mode, 0 otherwise

    NTP Extension Field: Extended Information, Version 0 Content Fields

   Example: A system that wants to convey an offset to TAI of 36
   seconds, and show it is in interleave mode.

    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 (0x0009)        |   Field Length (0x0008)       |
   +-------------------------------+-------------------------------+
   |            0x0003             |           0x0124              |
   +-------------------------------+-------------------------------+

           NTP Extension Field: Extended Information V0, Example

3.  Acknowledgements

   The author wishes to acknowledge the contributions of Martin Burnicki
   and Sam Weiler.

4.  IANA Considerations

   This memo requests IANA to allocate NTP Extension Field Type

      0x0009 (Extended-Information, Version 0)

   for this proposal.

5.  Security Considerations

   No unusual or special security considerations are known to be
   associated with this proposal.








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6.  Normative References

   [RFC0958]  Mills, D., "Network Time Protocol (NTP)", RFC 958,
              DOI 10.17487/RFC0958, September 1985,
              <https://www.rfc-editor.org/info/rfc958>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc5905>.

Author's Address

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

   Email: stenn@nwtime.org


























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