[ntpwg] ntp extension

[Danny Mayer]

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

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.