[ntpwg] Antw: Re: New Version Notification for draft-ietf-ntp-network-time-security-12.txt and draft-ietf-ntp-using-nts-for-ntp-03.txt

["Ulrich Windl" <[e-mail]>]

>>> Danny Mayer <[e-mail]> schrieb am 23.12.2015 um 22:58 in Nachricht
<[e-mail]>:
> On 12/23/2015 4:13 PM, Harlan Stenn wrote:
>> Danny Mayer writes:
>>> ... The problem is that a
>>> MAC extension field needs to be specified so that it can replace the
>>> existing MAC field. I'm also considering allowing for multiple MAC
>>> extension fields in a single packet so that one MAC hashing algorithm
>>> can be retired if found to be compromisable without disrupting NTP
>>> infrastructure and existing implementations. It also needs some
>>> discussion on usage by responding packets and which to use.
>> 
>> If this is a V4 thing there will be backward compatability issues.
>> 
> 
> No, not really. New code like NTS would use the new Extension Field but
> the MAC will need to be kept for older systems who won't be able to use
> NTS anyway.

Obviously in a transition period the servers need to provide both, the new MAC extension AND the old one, so old partners can ignore the MAC extension field and use the old MAC, while new partners will ignore(?) the old MAC and use the new one instead. Then the next generation can drop the old MAC. Maybe for consistency the transition version should check both MACS for consistency.

Ulrich

> 
>> I think I have an idea about how to do this so older systems might still
>> work.  It will require more research though.
> 
> The older systems won't know about the NTS stuff so it doesn't matter.
> The MAC itself can't go away until v5.
> 
> Danny
> 
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