Re: [TICTOC] [Ntp] WGLC for draft-ietf-ntp-mac

Hi Tal, Thanks for your comments.

Major comments:
> - This may have been discussed before, but still I am not sure what the
> answer is: it seems to make sense to define this new MAC as a dedicated
> extension field. Any reason not to do that? Since this draft deprecates the
> previous MD5-based MAC, there are no backward compatibility considerations.
>

The draft does not require the use of a new extension field. It works with
NTP's legacy MAC fields.  As Harlan mentioned earlier, the key ID maps to
two items--the key and the algorithm number. We decided not to introduce a
new extension field to keep things simple for implementations.

> - To allow algorithm agility, I would suggest to add a field that
> specifies the algorithm + a corresponding IANA registry.
>
> This NTP MAC draft only works for the setting of a pre-shared key (PSK)
for legacy NTP.

For asymmetric keys, we need to use NTS.

Given that we are stuck with the PSK model, we can still support algorithm
agility by specifying the MAC algorithm as part of the process of
configuring the PSK. Specifically, the ntp config file maps the key ID to a
secret key and MAC algorithm number.

> Less major comments:
> - Missing security considerations section.
>

Yes, will add.

> - Missing IANA considerations section.
>

Given the way we are dealing with algorithm agility, I don't think IANA
considerations are relevant.

> - "any extension fields that are present" => "every extension fields that
> is present".
>
> Thanks.
Sharon

> On Wed, Aug 9, 2017 at 7:53 AM, Karen O'Donoghue <odonoghue@isoc.org>
> wrote:
>
>> Folks,
>>
>> This begins a three week working group last call (WGLC) for "Message
>> Authentication Code for the Network Time Protocol"
>> https://datatracker.ietf.org/doc/draft-ietf-ntp-mac/
>>
>> Please review and provide comments to the mailing list by no later than
>> 31 August 2017. Earlier comments and discussion would be appreciated.
>> Please note that the chairs will be using this WGLC to determine consensus
>> to move this document forward to the IESG.
>>
>> Also, as a reminder, we have migrated the working group mailing list to
>> IETF infrastructure. Please respond to ntp@ietf.org.
>>
>> Regards,
>> Karen and Dieter
>>
>> _______________________________________________
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>>
>
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>

-- 
Sharon Goldberg
Computer Science, Boston University
http://www.cs.bu.edu/~goldbe