Internet Engineering Task Force H. Stenn
Internet-Draft Network Time Foundation
Intended status: Standards Track October 23, 2016
Expires: April 26, 2017
Network Time Protocol I-Do Extension Field
draft-stenn-ntp-i-do-02
Abstract
The first implementation of NTPv4 was released in 2003. NTPv4 is
defined by RFC 5905 [RFC5905]. It contains a public-key security
protocol, autokey, which is defined by RFC 5906 [RFC5906]. Until
very recently, autokey has been the only defined "user" of NTP packet
Extension Fields. New proposals for extension fields are being
written and there is currently no convenient way to learn if a remote
instance of NTP supports any extension fields or not. This proposal
contains a method to tell a remote instance of NTP what we (are
willing to admit we) support, and ask what they (are willing to admit
they) support.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 26, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. The I-Do Extension Field . . . . . . . . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. Normative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The first implementation of NTPv4 was released in 2003. NTPv4 is
defined by RFC 5905 [RFC5905]. It contains a public-key security
protocol, autokey, which is defined by RFC 5906 [RFC5906]. Until
very recently, autokey has been the only defined "user" of NTP packet
Extension Fields. New proposals for extension fields are being
written and there is currently no convenient way to learn if a remote
instance of NTP supports any extension fields or not. This proposal
contains a method to tell a remote instance of NTP what we (are
willing to admit we) support, and ask what they (are willing to admit
they) support.
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 I-Do Extension Field
If an incoming packet contains an unrecognized extension field, one
of two things will happen. While that extension field SHOULD be
ignored, an implementation MAY choose to drop the entire packet. If
an extension field is present there ordinarily SHOULD be a MAC
following the extension field. Some extension fields are unable to
be "signed" by a MAC, regardless of whether or not that MAC is a
traditional MAC or an extension field MAC.
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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 |
+-------------------------------+-------------------------------+
| I-Do 1 | ... |
+-------------------------------+-------------------------------+
| I-Do N | Padding |
+---------------------------------------------------------------+
NTP Extension Field: REFID Suggestion
Field Type: TBD (Recommendation for IANA: 0x0007 (I-Do, MAC
required), 0x2007 (I-Do, MAC OPTIONAL), 0x8007 (I-Do Response, MAC
required), 0xA007 I-Do Response, MAC OPTIONAL))
Field Length: as needed
Payload: An enumeration of the suppported base Field Types, followed
by any padding, 0x0000, needed to fill the payload to the desired
32-bit boundary.
Example: A system that wants to advertise support for Autokey and
I-Do, sending to a system that wants to advertise support for I-Do,
NTS, and MAC-As-Extension-Field
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 (0x2007) | Field Length (0x0008) |
+-------------------------------+-------------------------------+
| 0x0007 | 0x0002 |
+-------------------------------+-------------------------------+
NTP Extension Field: I-Do
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 (0xA007) | Field Length (0x000a) |
+-------------------------------+-------------------------------+
| 0x0003 | 0x0004 |
+-------------------------------+-------------------------------+
| 0x0007 | 0x0000 |
+-------------------------------+-------------------------------+
NTP Extension Field: I-Do Response
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The sender of any I-Do extension field MUST send an extension field
with a Field Type of 0x0007 (I-Do, MAC required) or 0x2007 (I-Do, MAC
OPTIONAL) and SHOULD include a paylod with any 0x0000 padding values
after enumerating the supported base Extension Field Types. If the
responding system recognizes the I-Do extension field, its response
MUST include an extension field with a Field Type of 0x8007 (I-Do
Response, MAC required) or 0xA007 (I-Do Response, MAC OPTIONAL), and
SHOULD include a paylod with any 0x0000 padding values after
enumerating the supported base Extension Field Types.
The following information is included here until it is specified in a
better location. If the Field Type does not have bit 0x2000 set,
there MUST be a MAC included later in the packet for this extension
field to be accepted. If the Field Type has bit 0x2000 set, the
presence of a MAC later in the packet is OPTIONAL.
Any system that receives an I-Do extension field as either an "offer"
or a "response" SHOULD scan the entire payload looking for nonzero
values that specify the capabilities of the remote association.
Any system that receives an I-Do "offer", 0x0007 or 0x2007, SHOULD
reply with an I-Do "response", 0x8007 or 0xA007.
Any system that sends an I-Do "offer" or "response" may send as few
or as many of its supported Field Types as it chooses. At any
subsequent time, either side may re-negotiate the list of supported
field types it is prepared to accept from the other system by sending
a new I-Do extension field.
The most-recently received I-Do list replaces any previous I-Do list.
3. IANA Considerations
This memo requests IANA to allocate NTP Extension Field Types:
0x0007 (I-DO)
0x2007 (I-DO, MAC OPTIONAL)
0x8007 (I-DO Response)
0xA007 (I-DO Response, MAC OPTIONAL)
and I-DO types:
0xFFFE (I-DO Leap Smear REFIDs)
0xFFFF (I-DO IPv6 REFID hash)
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for this proposal.
4. Security Considerations
Additional information TBD
5. 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,
<http://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,
<http://www.rfc-editor.org/info/rfc5905>.
[RFC5906] Haberman, B., Ed. and D. Mills, "Network Time Protocol
Version 4: Autokey Specification", RFC 5906,
DOI 10.17487/RFC5906, June 2010,
<http://www.rfc-editor.org/info/rfc5906>.
Author's Address
Harlan Stenn
Network Time Foundation
P.O. Box 918
Talent, OR 97540
US
Email: stenn@nwtime.org
Stenn Expires April 26, 2017 [Page 5]
