Network Time Protocol I-Do Extension Field
draft-stenn-ntp-i-do-00

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 support, and ask what they support.

Status of This Memo

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This Internet-Draft will expire on September 15, 2016.

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Table of Contents

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

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 support, and ask what 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. Either that extension field will be ignored, or the entire packet will be dropped. 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.

 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), 0x4007 (I-Do Response, MAC required), 0x6007 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.

 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 (0x6007)        |   Field Length (0x000a)       |
+-------------------------------+-------------------------------+ 
|            0x0003             |           0x0004              | 
+-------------------------------+-------------------------------+ 
|            0x0007             |           0x0000              | 
+-------------------------------+-------------------------------+

NTP Extension Field: I-Do Response

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

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. The responding system MUST reply with an extension field with a Field Type of 0x4007 (I-Do Response, MAC required) or 0x6007 (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 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", 0x4007 or 0x6007.

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. 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.

5. Security Considerations

Additional information TBD

6. Normative References

Author's Address