Network Time Protocol Version 4 (NTPv4) Extension Fields
RFC 7822
| Document | Type |
RFC - Proposed Standard
(March 2016; No errata)
Updates RFC 5905
|
|
|---|---|---|---|
| Last updated | 2016-03-30 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | Submitted to IESG for Publication Apr 2016 | |
| Document shepherd | Karen O'Donoghue | ||
| Shepherd write-up | Show (last changed 2015-08-13) | ||
| IESG | IESG state | RFC 7822 (Proposed Standard) | |
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Brian Haberman | ||
| Send notices to | (None) | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | No IC | ||
Internet Engineering Task Force (IETF) T. Mizrahi
Request for Comments: 7822 Marvell
Updates: 5905 D. Mayer
Category: Standards Track Network Time Foundation
ISSN: 2070-1721 March 2016
Network Time Protocol Version 4 (NTPv4) Extension Fields
Abstract
The Network Time Protocol version 4 (NTPv4) defines the optional
usage of extension fields. An extension field, as defined in RFC
5905, is an optional field that resides at the end of the NTP header
and that can be used to add optional capabilities or additional
information that is not conveyed in the standard NTP header. This
document updates RFC 5905 by clarifying some points regarding NTP
extension fields and their usage with Message Authentication Codes
(MACs).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7822.
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
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.
Mizrahi & Mayer Standards Track [Page 1]
RFC 7822 NTP Extension Fields March 2016
Table of Contents
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................3
2.1. Terminology ................................................3
2.2. Terms and Abbreviations ....................................3
3. NTP Extension Fields - RFC 5905 Update ..........................3
4. Security Considerations .........................................6
5. References ......................................................7
5.1. Normative References .......................................7
5.2. Informative References .....................................7
Acknowledgments ....................................................8
Authors' Addresses .................................................8
1. Introduction
The NTP header format consists of a set of fixed fields that may be
followed by some optional fields. Two types of optional fields are
defined: Message Authentication Codes (MACs), and extension fields as
defined in Section 7.5 of [NTPv4].
If a MAC is used, it resides at the end of the packet. This field
can be either 24 octets long, 20 octets long, or a 4-octet
crypto-NAK.
NTP extension fields were defined in [NTPv4] as a generic mechanism
that allows the addition of future extensions and features without
modifying the NTP header format (Section 16 of [NTPv4]).
The only currently defined extension fields are those fields used by
the Autokey protocol [Autokey] and the Checksum Complement [RFC7821].
The Autokey extension field is always followed by a MAC, and
Section 10 of [Autokey] specifies the parsing rules that allow a host
to distinguish between an extension field and a MAC. However, a MAC
is not mandatory after an extension field; an NTPv4 packet can
include one or more extension fields without including a MAC. This
behavior is specified in Section 7.5 of [NTPv4] and in [Err3627], and
is further clarified in this document.
This document updates [NTPv4] (RFC 5905) by clarifying some points
regarding the usage of extension fields. These updates include
changes to address errors found after the publication of [NTPv4] with
respect to extension fields. Specifically, this document updates
Section 7.5 of [NTPv4], clarifying the relationship between extension
fields and MACs, and defining the behavior of a host that receives an
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