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Network Working Group                                           D. Mills
Internet-Draft                                    University of Delaware
Intended status: Informational                        K. O'Donoghue, Ed.
Expires: May 3, 2012                                    Internet Society
                                                                 D. Hart

                                                                H. Stenn
                                           Network Time Foundation, Inc.
                                                        October 31, 2011


 Control Messages Protocol for Use with Network Time Protocol Version 4
                    draft-odonoghue-ntpv4-control-01

Abstract

   This document describes the structure of the control messages used
   with the Network Time Protocol.  These control messages can be used
   to monitor and control the Network Time Protocol application running
   on any IP network attached computer.  The information in this
   informational RFC was originally described in Appendix B of RFC 1305.

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 May 3, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   carefully, as they describe your rights and restrictions with respect
   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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
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   it for publication as an RFC or to translate it into languages other
   than English.


































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  NTP Control Message Format . . . . . . . . . . . . . . . . . .  6
   3.  Status Words . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.1.  System Status Word . . . . . . . . . . . . . . . . . . . .  8
     3.2.  Peer Status Word . . . . . . . . . . . . . . . . . . . . . 10
     3.3.  Clock Status Word  . . . . . . . . . . . . . . . . . . . . 12
     3.4.  Error Status Word  . . . . . . . . . . . . . . . . . . . . 13
   4.  Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18


































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1.  Introduction

   Editor's Note (to be removed prior to publication): The text below is
   taken directly from RFC 1305.  Input is requested to update the text
   to reflect current practice.  This is required to fully obsolete RFC
   1305.

   In a comprehensive network-management environment, facilities are
   presumed available to perform routine NTP control and monitoring
   functions, such as setting the leap-indicator bits at the primary
   servers, adjusting the various system parameters and monitoring
   regular operations.  Ordinarily, these functions can be implemented
   using a network-management protocol such as SNMP and suitable
   extensions to the MIB database.  However, in those cases where such
   facilities are not available, these functions can be implemented
   using special NTP control messages described herein.  These messages
   are intended for use only in systems where no other management
   facilities are available or appropriate, such as in dedicated-
   function bus peripherals.  Support for these messages is not required
   in order to conform to this specification.

   The NTP Control Message has the value 6 specified in the mode field
   of the first octet of the NTP header and is formatted as shown below.
   The format of the data field is specific to each command or response;
   however, in most cases the format is designed to be constructed and
   viewed by humans and so is coded in free-form ASCII.  This
   facilitates the specification and implementation of simple management
   tools in the absence of fully evolved network-management facilities.
   As in ordinary NTP messages, the authenticator field follows the data
   field.  If the authenticator is used the data field is zero-padded to
   a 32-bit boundary, but the padding bits are not considered part of
   the data field and are not included in the field count.

   IP hosts are not required to reassemble datagrams larger than 576
   octets; however, some commands or responses may involve more data
   than will fit into a single datagram.  Accordingly, a simple
   reassembly feature is included in which each octet of the message
   data is numbered starting with zero.  As each fragment is transmitted
   the number of its first octet is inserted in the offset field and the
   number of octets is inserted in the count field.  The more-data (M)
   bit is set in all fragments except the last.

   Most control functions involve sending a command and receiving a
   response, perhaps involving several fragments.  The sender chooses a
   distinct, nonzero sequence number and sets the status field and R and
   E bits to zero.  The responder interprets the opcode and additional
   information in the data field, updates the status field, sets the R
   bit to one and returns the three 32-bit words of the header along



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   with additional information in the data field.  In case of invalid
   message format or contents the responder inserts a code in the status
   field, sets the R and E bits to one and, optionally, inserts a
   diagnostic message in the data field.

   Some commands read or write system variables and peer variables for
   an association identified in the command.  Others read or write
   variables associated with a radio clock or other device directly
   connected to a source of primary synchronization information.  To
   identify which type of variable and association a 16-bit association
   identifier is used.  System variables are indicated by the identifier
   zero.  As each association is mobilized a unique, nonzero identifier
   is created for it.  These identifiers are used in a cyclic fashion,
   so that the chance of using an old identifier which matches a newly
   created association is remote.  A management entity can request a
   list of current identifiers and subsequently use them to read and
   write variables for each association.  An attempt to use an expired
   identifier results in an exception response, following which the list
   can be requested again.

   Some exception events, such as when a peer becomes reachable or
   unreachable, occur spontaneously and are not necessarily associated
   with a command.  An implementation may elect to save the event
   information for later retrieval or to send an asynchronous response
   (called a trap) or both.  In case of a trap the IP address and port
   number is determined by a previous command and the sequence field is
   set as described below.  Current status and summary information for
   the latest exception event is returned in all normal responses.  Bits
   in the status field indicate whether an exception has occurred since
   the last response and whether more than one exception has occurred.

   Commands need not necessarily be sent by an NTP peer, so ordinary
   access-control procedures may not apply; however, the optional mask/
   match mechanism suggested in [RFC5905] provides the capability to
   limit mode 6 processing to selected address ranges.

   The Network Time Protocol reference implementation maintained by the
   University of Delaware and ntp.org provides a utility program, ntpq
   which enables management and configuration of the ntpd daemon using
   NTP Control Messages (mode 6).  A related utility program, ntpdc,
   uses an earlier, deprecated implementation-specific binary management
   protocol using NTP mode 7 datagrams.  Due to the implementation
   complexity of the earlier protocol, the reference implementation has
   added support for all operations that previously were exposed only
   via mode 7 to the preferred mode 6 interface.  Support for mode 7
   requests is likely to be disabled by default in the reference
   implementation's daemon.




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2.  NTP Control Message Format

   The format of the NTP Control Message header, which immediately
   follows the UDP header, is shown below.  Following is a description
   of its fields.  Bit positions marked as zero are reserved and should
   always be transmitted as zero.

    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
   +---+-----+-----+-----+---------+-------------------------------+
   |LI | VN  |Mode |R E M|    Op   |           Sequence            |
   +---+-----+-----+-----+---------+-------------------------------+
   |            Status             |        Association ID         |
   +-------------------------------+-------------------------------+
   |            Offset             |             Count             |
   +-------------------------------+-------------------------------+
   |                                                               |
   |                             Data                              |
   |                     (468 octets or less)                      |
   |                                                               |
   |               +-----------------------------------------------+
   |               | Padding as needed to next multiple of 32 bits |
   +---------------+-----------------------------------------------+
   |          Authenticator (optional, 96 octets or less)          |
   +---------------------------------------------------------------+

   LI: This is a two-bit integer that must be zero for control message
   requests and responses.  The Leap Indicator value used at this
   position in most NTP modes is in the System Status Word provided in
   some control message responses.

   Version Number (VN): This is a three-bit integer indicating a minimum
   NTP version number.  NTP servers should not respond to control
   messages with an unrecognized version number.  Requests may
   intentionally use a lower version number to enable interoperability
   with earlier versions.  The reference implementation utility ntpq
   uses version 2 by default.  Responses must carry the same version as
   the corresponding request.

   Mode: This is a three-bit integer indicating the mode.  It must have
   the value 6, indicating an NTP control message.

   Response Bit (R): Set to zero for commands, one for responses.

   Error Bit (E): Set to zero for normal response, one for error
   response.

   More Bit (M): Set to zero for last fragment, one for all others.



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   Operation Code (Op): This is a five-bit integer specifying the
   command function.  The values are:

   +-------+--------------------------------------------------+
   |  Code |                     Meaning                      |
   +-------+--------------------------------------------------+
   |   0   | reserved                                         |
   |   1   | read status command/response                     |
   |   2   | read variables command/response                  |
   |   3   | write variables command/response                 |
   |   4   | read clock variables command/response            |
   |   5   | write clock variables command/response           |
   |   6   | set trap address/port command/response           |
   |   7   | trap response                                    |
   |   8   | runtime configuration command/response           |
   |   9   | export configuration to file command/response    |
   |  10   | retrieve remote address stats command/response   |
   |  11   | retrieve local address stats command/response    |
   |  12   | request client-specific nonce command/response   |
   | 13-30 | reserved for future use                          |
   |  31   | unset trap address/port command/response         |
   +-------+--------------------------------------------------+

   Sequence: This is a 16-bit integer indicating the sequence number.
   Each request should use a different sequence number.  Each response
   carries the same sequence number as its corresponding request.  For
   asynchronous trap responses, the responder increments the sequence
   number by one each response, allowing trap receivers to detect
   missing trap responses.  Note the sequence number of each fragment in
   a multiple-datagram response carries the same sequence number, copied
   from the request.

   Status: This is a 16-bit code indicating the current status of the
   system, peer or clock, with values coded as described in following
   sections.

   Association ID: This is a 16-bit unsigned integer identifying a valid
   association, or zero for the system clock.

   Offset: This is a 16-bit unsigned integer indicating the offset, in
   octets, of the first octet in the data area.  The offset must be zero
   in requests.  Responses spanning multiple datagrams use a positive
   offset in all but the first datagram.

   Count: This is a 16-bit unsigned integer indicating the length of the
   data, in octets

   Data: This contains the message data for the command or response.



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   The maximum number of data octets is 468.

   Padding: Contains zero to three octets with value zero, as needed to
   ensure the overall control message size is a multiple of 4 octets.

   Authenticator (optional): When an NTP authentication mechanism is
   used, this contains the message authenticator information defined in
   section 7.3 of [RFC5905].


3.  Status Words

   Status words indicate the present status of the system, associations
   and clock.  They are designed to be interpreted by network-monitoring
   programs and are in one of four 16-bit formats shown in Figure 6 and
   described in this section.  System and peer status words are
   associated with responses for all commands except the read clock
   variables, write clock variables and set trap address/port commands.
   The association identifier zero specifies the system status word,
   while a nonzero identifier specifies a particular peer association.
   The status word returned in response to read clock variables and
   write clock variables commands indicates the state of the clock
   hardware and decoding software.  A special error status word is used
   to report malformed command fields or invalid values.

3.1.  System Status Word

   The system status word appears in the status field of the response to
   a read status or read variables command with a zero association
   identifier.  The format of the system status word is as follows:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +---+-----------+-------+-------+
   |LI | ClockSrc  | Count | Code  |
   +---+-----------+-------+-------+

   Leap Indicator (LI): This is a two-bit code warning of an impending
   leap second to be inserted/deleted in the last minute of the current
   day, with bit 0 and bit 1, respectively, coded as follows: (EDITOR:
   this could refer to RFC 5905 section 7.3 figure 9 instead.)










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   +------+------------------------------------------------------------+
   |  LI  |                       Meaning                              |
   +------+------------------------------------------------------------+
   |  00  | no warning                                                 |
   |  01  | insert second after 23:59:59 of the current day            |
   |  10  | delete second 23:59:59 of the current day                  |
   |  11  | unsynchronized                                             |
   +------+------------------------------------------------------------+

   ClockSrc: This is a six-bit integer indicating the current
   synchronization source, with values coded as follows:

   +-------+-----------------------------------------------------------+
   |  Code |                     Meaning                               |
   +-------+-----------------------------------------------------------+
   |   0   | unspecified or unknown                                    |
   |   1   | Calibrated atomic clock (e.g.,, PPS,, HP 5061)            |
   |   2   | VLF (band 4) or LF (band 5) radio (e.g.,, OMEGA,, WWVB)   |
   |   3   | HF (band 7) radio (e.g.,, CHU,, MSF,, WWV/H)              |
   |   4   | UHF (band 9) satellite (e.g.,, GOES,, GPS)                |
   |   5   | local net (e.g.,, DCN,, TSP,, DTS)                        |
   |   6   | UDP/NTP                                                   |
   |   7   | UDP/TIME                                                  |
   |   8   | eyeball-and-wristwatch                                    |
   |   9   | telephone modem (e.g.,, NIST)                             |
   | 10-63 | reserved                                                  |
   +-------+-----------------------------------------------------------+

   System Event Counter: This is a four-bit integer indicating the
   number of system events occurring since the last time the System
   Event Code changed.  Upon reaching 15, subsequent events with the
   same code are not counted.

   System Event Code: This is a four-bit integer identifying the latest
   system exception event, with new values overwriting previous values,
   and coded as follows:















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+-------+---------------------------------------------------------------+
|  Code |                         Meaning                               |
+-------+---------------------------------------------------------------+
|   0   | unspecified                                                   |
|   1   | frequency correction (drift) file not available               |
|   2   | frequency correction started (frequency stepped)              |
|   3   | spike detected and ignored, starting stepout timer            |
|   4   | frequency training started                                    |
|   5   | clock synchronized                                            |
|   6   | system restart                                                |
|   7   | panic stop (required step greater than panic threshold)       |
|   8   | no system peer                                                |
|   9   | leap second insertion/deletion armed for end of current month |
|  10   | leap second disarmed                                          |
|  11   | leap second inserted or deleted                               |
|  12   | clock stepped (stepout timer expired)                         |
|  13   | kernel loop discipline status changed                         |
|  14   | leapseconds table loaded from file                            |
|  15   | leapseconds table outdated, updated file needed               |
+-------+---------------------------------------------------------------+

3.2.  Peer Status Word

   A peer status word is returned in the status field of a response to a
   read status, read variables or write variables command and appears
   also in the list of association identifiers and status words returned
   by a read status command with a zero association identifier.  The
   format of a peer status word is as follows:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +---------+-----+-------+-------+
   |  Flags  | Sel | Count | Code  |
   +---------+-----+-------+-------+

   Peer Status Flags: This is a set of five bits indicating the status
   of the peer determined by the packet procedure, with bits assigned as
   follows:













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+--------+--------+--------------------------------------------------------+
| Peer   |        |                                                        |
| Status |        |                                                        |
| Flag   |        |                                                        |
| Bit    | Value  |                     Meaning                            |
+--------+--------+--------------------------------------------------------+
|    0   | 0x8000 | configured (peer.config)                               |
|    1   | 0x4000 | authentication enabled (peer.authenable)               |
|    2   | 0x2000 | authentication okay (peer.authentic)                   |
|    3   | 0x1000 | reachable (peer.reach != 0)                            |
|    4   | 0x0800 | broadcast association                                  |
+--------+--------+--------------------------------------------------------+

   Peer Selection (Sel): This is a three-bit integer indicating the
   status of the peer determined by the clock-selection procedure, with
   values coded as follows:

+-------+---------------------------------------------------------------------+
|  Peer |                                                                     |
|  Sel  |                        Meaning                                      |
+-------+---------------------------------------------------------------------+
|   0   | rejected                                                            |
|   1   | discarded by intersection algorithm                                 |
|   2   | discarded by table overflow (not currently used)                    |
|   3   | discarded by the cluster algorithm                                  |
|   4   | included by the combine algorithm                                   |
|   5   | backup source (with more than sys.maxclock survivors)               |
|   6   | system peer (synchronization source)                                |
|   7   | PPS (pulse per second) peer                                         |
+-------+---------------------------------------------------------------------+

   Peer Event Counter: This is a four-bit integer indicating the number
   of peer events that occurred since the last time the peer event code
   changed.  Upon reaching 15, subsequent events with the same code are
   not counted.

   Peer Event Code: This is a four-bit integer identifying the latest
   peer exception event, with new values overwriting previous values,
   and coded as follows:












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+--------+---------------------------------------------------------------------+
| Peer   |                                                                     |
| Event  |                            Meaning                                  |
| Code   |                                                                     |
+--------+---------------------------------------------------------------------+
|    0   | unspecified                                                         |
|    1   | association mobilized                                               |
|    2   | association demobilized                                             |
|    3   | peer unreachable                                                    |
|    4   | peer reachable                                                      |
|    5   | association restarted or timed out                                  |
|    6   | no reply (used only with one-shot ntpd -q, known as ntpdate mode)   |
|    7   | peer rate limit exceeded (kiss code RATE received)                  |
|    8   | access denied (kiss code DENY received), not currently implemented  |
|    9   | leap second insertion/deletion at month's end armed by peer vote    |
|   10   | became system peer (sys.peer)                                       |
|   11   | reference clock event (see clock status word)                       |
|   12   | authentication failed                                               |
|   13   | popcorn spike suppressed by peer clock filter register              |
|   14   | entering interleaved mode                                           |
|   15   | recovered from interleave error                                     |
+--------+---------------------------------------------------------------------+

3.3.  Clock Status Word

   There are two ways a reference clock can be attached to a NTP service
   host, as an dedicated device managed by the operating system and as a
   synthetic peer managed by NTP.  As in the read status command, the
   association identifier is used to identify which one, zero for the
   system clock and nonzero for a peer clock.  Only one system clock is
   supported by the protocol, although many peer clocks can be
   supported.  A system or peer clock status word appears in the status
   field of the response to a read clock variables or write clock
   variables command.  This word can be considered an extension of the
   system status word or the peer status word as appropriate.  The
   format of the clock status word is as follows:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +---------------+-------+-------+
   |   Reserved    | Count | Code  |
   +---------------+-------+-------+

   Reserved: An eight-bit integer that should be ignored by requesters
   and zeroed by responders.

   Clock Event Counter: This is a four-bit integer indicating the number
   of clock events that occurred since the last time the clock event



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   code changed.  Upon reaching 15, subsequent events with the same code
   are not counted.

   Clock Event Code: This is a four-bit integer indicating the current
   clock status, with values coded as follows:

+--------------+------------------------------------------------------------+
| Clock Status |                      Meaning                               |
+--------------+------------------------------------------------------------+
|       0      | clock operating within nominals                            |
|       1      | reply timeout                                              |
|       2      | bad reply format                                           |
|       3      | hardware or software fault                                 |
|       4      | propagation failure (loss of signal)                       |
|       5      | bad date format or value                                   |
|       6      | bad time format or value                                   |
|      7-15    | reserved                                                   |
+--------------+------------------------------------------------------------+

3.4.  Error Status Word

   An error status word is returned in the status field of an error
   response as the result of invalid message format or contents.  Its
   presence is indicated when the E (error) bit is set along with the
   response (R) bit in the response.  The format of the Error Status
   Word is:

    0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +---------------+---------------+
   |  Error Code   |   Reserved    |
   +---------------+---------------+

   Error code: an eight-bit integer coded as follows:

+--------------+------------------------------------------------------------+
| Error Status |                    Meaning                                 |
+--------------+------------------------------------------------------------+
|       0      | unspecified                                                |
|       1      | authentication failure                                     |
|       2      | invalid message length or format                           |
|       3      | invalid opcode                                             |
|       4      | unknown association identifier                             |
|       5      | unknown variable name                                      |
|       6      | invalid variable value                                     |
|       7      | administratively prohibited                                |
|     8-255    | reserved                                                   |
+--------------+------------------------------------------------------------+



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   Reserved: Responders should use zero.  Requesters should ignore the
   Reserved value to preserve the possibility of future use.


4.  Commands

   Commands consist of the header and optional data field shown in
   Section 3.  When present, the data field contains a list of
   identifiers or assignments in the form
   <<identifier>>[=<<value>>],<<identifier>>[=<<value>>],... where
   <<identifier>> is the ASCII name of a system or peer variable
   specified in Sections 9.1 and 11.1 of RFC 5905 and <<value>> is
   expressed as a decimal, hexadecimal or string constant in the syntax
   of the C programming language.  Where no ambiguity exists, the "s."
   or "p." prefixes shown in Figure 5 of Section 7.1 of RFC 5905
   [RFC5905] can be suppressed.  Whitespace (ASCII nonprinting format
   effectors) can be added to improve readability for simple monitoring
   programs that do not reformat the data field.  Internet Protocol
   version 4 addresses are represented as four decimal octets without
   leading zeros, separated by dots.  Internet Protocol version 6
   addresses are represented as mandated by [RFC5952], without
   surrounding square brackets unless a port specification is combined
   with the address.  Timestamps, including reference, originate,
   receive and transmit values, as well as the logical clock, are
   represented in units of seconds and fractions, preferably in
   hexadecimal notation, while delay, offset, dispersion and distance
   values are represented in units of milliseconds and fractions,
   preferably in decimal notation.  All other values are represented
   as-is, preferably in decimal notation.

   Implementations may define variables other than those listed in
   Figures 6, 7, 16, 17, 18, 19, 27 and 29 of RFC 5905.  Called
   extramural variables, these are distinguished by the inclusion of
   some character type other than alphanumeric or "." in the name.  For
   those commands that return a list of assignments in the response data
   field, if the command data field is empty, it is expected that all
   available variables defined in Figures 6, 7 and 17 of RFC 5905 will
   be included in the response.  For the read commands, if the command
   data field is nonempty, an implementation may choose to process this
   field to individually select which variables are to be returned.

   Commands are interpreted as follows:

   Read Status (1): The command data field is empty or contains a list
   of identifiers separated by commas.  The command operates in two ways
   depending on the value of the association identifier.  If this
   identifier is nonzero, the response includes the peer identifier and
   status word.  Optionally, the response data field may contain other



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   information, such as described in the Read Variables command.  If the
   association identifier is zero, the response includes the system
   identifier (0) and status word, while the data field contains a list
   of binary-coded pairs <<association identifier>> <<status word>>, one
   for each currently defined association.

   Read Variables (2): The command data field is empty or contains a
   list of identifiers separated by commas.  If the association
   identifier is nonzero, the response includes the requested peer
   identifier and status word, while the data field contains a list of
   peer variables and values as described above.  If the association
   identifier is zero, the data field contains a list of system
   variables and values.  If a peer has been selected as the
   synchronization source, the response includes the peer identifier and
   status word; otherwise, the response includes the system identifier
   (0) and status word.

   Write Variables (3): The command data field contains a list of
   assignments as described above.  The variables are updated as
   indicated.  The response is as described for the Read Variables
   command.

   Read Clock Variables (4): The command data field is empty or contains
   a list of identifiers separated by commas.  The association
   identifier selects the system clock variables or peer clock variables
   in the same way as in the Read Variables command.  The response
   includes the requested clock identifier and status word and the data
   field contains a list of clock variables and values, including the
   last timecode message received from the clock.

   Write Clock Variables (5): The command data field contains a list of
   assignments as described above.  The clock variables are updated as
   indicated.  The response is as described for the Read Clock Variables
   command.  The reference implementation daemon requires authentication
   for this command.

   Set Trap Address/Port (6): The command association identifier, status
   and data fields are ignored.  The address and port number for
   subsequent trap messages are taken from the source address and port
   of the control message itself.  The initial trap counter for trap
   response messages is taken from the sequence field of the command.
   The response association identifier, status and data fields are not
   significant.  Implementations should include sanity timeouts which
   prevent trap transmissions if the monitoring program does not renew
   this information after a lengthy interval.

   Trap Response (7): This command differs from the others described
   here, which are initiated by a management agent (such as ntpq) and



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   responded to by a NTP daemon.  Trap Response is sent by a NTP daemon
   to any registered trap receivers when a system, peer or clock
   exception event occurs.  The opcode field is 7 and the R bit is set.
   The trap counter is incremented by one for each trap sent and the
   sequence field set to that value.  The trap message is sent using the
   IP address and port fields established by the set trap address/port
   command.  If a system trap the association identifier field is set to
   zero and the status field contains the system status word.  If a peer
   trap the association identifier field is set to that peer and the
   status field contains the peer status word.  Optional ASCII-coded
   information can be included in the data field.

   Configure (8): The command data is parsed and applied as if supplied
   in the daemon configuration file.  The reference implementation
   daemon requires authentication for this command.

   Save Configuration (9): Write a snapshot of the current configuration
   to the file name supplied as the command data.  The reference
   implementation daemon requires authentication for this command.
   Further, the command is refused unless a directory in which to store
   the resulting files has been explicitly configured by the operator.

   Read MRU (10): Retrieves records of recently seen remote addresses
   and associated statistics.  Command data consists of name=value pairs
   controlling the selection of records, as well as a requestor-specific
   nonce previously retrieved using this command or opcode 12, Request
   Nonce.  The response consists of name=value pairs where some names
   can appear multiple times using a dot followed by a zero-based index
   to distinguish them, and to associate elements of the same record
   with the same index.  A new nonce is provided with each successful
   response.

   Read local address stats (11): Retrieves the local network addresses
   of the daemon with status and counters for each.  Command data is not
   used in the request.  Similar to Read MRU, some response information
   uses zero-based indexes as part of the variable name preceding the
   equals sign and value, where each index relates information for a
   single local address.  The reference implementation daemon requires
   authentication for this command.

   Request Nonce (12): Retrieves a 96-bit nonce specific to the
   requesting remote address, which is valid for a limited period.
   Command data is not used in the request.  The nonce consists of a 64-
   bit NTP timestamp and 32 bits of hash derived from that timestamp,
   the remote address, and salt known only to the server which varies
   between daemon runs.  The reference implementation honors nonces
   which were issued less than 16 seconds prior.  Regurgitation of the
   nonce by a managment agent demonstrates to the server that the agent



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   can receive datagrams sent to the source address of the request,
   making source address "spoofing" more difficult in a similar way as
   TCP's three-way handshake.

   Unset Trap (31): Removes the requesting remote address and port from
   the list of trap receivers.  Command data is not used in the request.
   If the address and port are not in the list of trap receivers, the
   error code is 4, bad association.


5.  IANA Considerations

   Editor's Note: To be reviewed by the working group prior to
   completion.


6.  Security Considerations

   Editor's Note: To be supplied by the working group prior to
   completion.


7.  Acknowledgements


8.  References

8.1.  Normative References

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

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952, August 2010.

8.2.  Informative References

   [RFC5906]  Haberman, B. and D. Mills, "Network Time Protocol Version
              4: Autokey Specification", RFC 5906, June 2010.

   [RFC5907]  Gerstung, H., Elliott, C., and B. Haberman, "Definitions
              of Managed Objects for Network Time Protocol Version 4
              (NTPv4)", RFC 5907, June 2010.

   [RFC5908]  Gayraud, R. and B. Lourdelet, "Network Time Protocol (NTP)
              Server Option for DHCPv6", RFC 5908, June 2010.




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Authors' Addresses

   Dr. David L. Mills
   University of Delaware
   Newark, Delaware
   US

   Email: mills@udel.edu


   Karen O'Donoghue (editor)
   Internet Society
   King George, Virginia
   US

   Email: odonoghue@isoc.org


   David L. Hart
   Redmond, Washington
   US

   Email: hart@ntp.org


   Harlan M. Stenn
   Network Time Foundation, Inc.
   Talent, Oregon
   US

   Email: stenn@ntp.org




















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