Subject: [ntpwg] More on poll interval

From: Kyle Rose <[email-masked]>
Date: Fri, 26 May 2017 16:24:08 -0400

https://tools.ietf.org/html/draft-ietf-ntp-data-minimization-00

§4.1 ¶3: q( Putting accurate information into this field has no significant
impact on privacy since an observer can already obtain this information
simply by observing the actual interval between requests. )

Sure, if the observer can already assign requests accurately to clients.
But if a client strictly follows the polling interval, isn't its inclusion
of the poll interval here mostly equivalent to its including the previous
response time in the receive timestamp field? ("Mostly" because it clearly
isn't true if packets are lost, for instance.) Seems like both would enable
the same kind of client tracking.

Kyle
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From: Harlan Stenn <[email-masked]>
Date: Fri, 26 May 2017 16:40:12 -0700

> the same kind of client tracking.

Folks are playing with a double-edged sword here.

In an ongoing association, the initiating side is letting the other side
know when it expects to send the next packet.  This is useful so the
other side can do a "gate" check.  Likewise, the other side might know
something the initiating side does not, and it can send back a different
poll interval as a suggestion(!) to the initiator that it alter its poll
interval.

Am I being too subtle?

-- 
Harlan Stenn <[email-masked]>
http://networktimefoundation.org - be a member!
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