[ntpwg] ntp extension

[TS Glassey]

----- Original Message ----- 
From: "Danny Mayer" <mayer at ntp.isc.org>
To: "Brian Haberman" <brian at innovationslab.net>
Cc: "Greg Dowd" <GDowd at symmetricom.com>; <ntpwg at ntp.isc.org>
Sent: Saturday, March 15, 2008 6:55 PM
Subject: Re: [ntpwg] ntp extension


> Recovering some space is good, but maybe we should question whether or
> not we can fix the problem with the algorithm so that it doesn't take up
> that kind of space.

External key management is really important too. CDSA or PKCS11/12 standard 
based key management is needed. AutoKEY is cool but it doesnt scale.

> If necessary we would have to rev the autokey
> version so that it's backward compatible with what currently exists.

Only if there is an insistance not to break other versions. This may nopt be 
such a bad thing.

>
> Danny
> Brian Haberman wrote:
>> Greg,
>>       Works for me.  Any objections?
>>
>> Regards,
>> Brian
>>
>> Greg Dowd wrote:
>>>   _NTP Extensions Field_
>>>
>>>
>>>
>>> TLV = Type, Length and Value
>>>
>>>
>>>
>>>
>>>
>>> Autokey is currently using ALL 65,535 types.  This violates the TLV
>>> principle.  The reason for this is that Autokey has redefined the Type
>>> field as a structure containing version and flag fields along with the
>>> original type id.
>>>
>>>
>>>
>>> Current type definition in the NTP document
>>>
>>> The Field Type field is specific to the defined function and is not
>>>
>>> elaborated here.
>>>
>>>
>>>
>>> Suggested definition in NTP document.
>>>
>>> The Field Type field is specific to the defined function and is not
>>>
>>> elaborated here.  TLV types are IANA registered numbers.
>>>
>>>
>>>
>>> Current type definition in the Autokey document
>>>
>>> The 8-bit Code field specifies the request or response operation,
>>>
>>> while the 4-bit Version Number (VN) field is 2 for the current
>>>
>>> protocol version.  There are four flag bits: bit 0 is the Response
>>>
>>> Flag (R) and bit 1 is the Error Flag (E); the other two bits are
>>>
>>> presently unused and should be set to 0.  The remaining fields will
>>>
>>> be described later.
>>>
>>>
>>>
>>> If we take the presently unused flag bits and force them to 0, we could
>>> recover some space for future use.
>>>
>>>
>>>
>>> Note that the 48000 TLVs currently in use by Autokey support about 20
>>> commands.  This is wasting 99.96% of the allocated space.  This is due
>>> to Autokey’s usage of the Type field as a compound structure
>>> incorporating not only commands but also a version and flags field.
>>>
>>>
>>>
>>> Types currently in use by Autokey (if flag fields are capped)
>>>
>>>
>>>
>>> 0x0000 – 0x0FFF
>>>
>>> 0x4000 – 0xFFFF
>>>
>>>
>>>
>>> Available for future use (if flag fields are capped)
>>>
>>>
>>>
>>> 0x1000 – 0x3FFF
>>>
>>>
>>>
>>> Result is that at least 25% of the space will be available for
>>> extensions of the protocol, which will be backwards compatible with the
>>> current proposed version.
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