[ntp:questions] NTPv4

Martin Burnicki martin.burnicki at burnicki.net
Fri Oct 6 14:13:53 UTC 2017


I unintentionally replied to a previous email directly, not via the
list. Sorry.

ST Intern wrote:
> Sorry, I might not be clear.

Indeed. ;-)

> I mean Yes.
> it was my question.
> So may I know if the w32time service shipped with Windows 10 uses NTP v4
> protocol?

I just made a quick test using wireshark. A Windows 10 client running
w32time still sends v3 request to the server.

However, why does this matter for your application?

The NTP base packet layout is anyway the same in the v3 and v4 protocol
specification.

Protocol NTPv3 specified a way to append cryptographic signatures to the
base packet.

Protocol v4 specifies some new extension fields which can optionally be
appended to the base packet.

These extension fields are optionally used by the reference
implementation, ntpd, for symmetric key authenticaation, for the
"autokey" feature, and soon for the new Network Time security extension,
NTS.

However, none of these extension fields have ever been used by w32time,
AFAIK, so it doesn't matter if the base packet contains the v3 or v4 ID.

On the other hand, again AFAIK, w32time can append a Windows-specific,
proprietary signature to the NTP base packet. However, this is not
compatible with the reference implementation, so if authentication is
used between w32time and ntpd, this won't work properly anyway.

If you have a pure Windows network then it doesn't matter at all which
version code is in the packets. How good this works depends only on how
accurately w32time can determine the client time offset to be
compensated, and how good and smoothly it can adjust the system time.

There have been very simple implementations in Windows XP / Server 2003,
and things have become much better with current versions of w32time, and
all these w32time versions were using "v3" packets.

So why do you think "v4" inside the packets improves anything?

Martin


> On Thu, Oct 5, 2017 at 11:25 AM, ST Intern <steeintern at gmail.com
> <mailto:steeintern at gmail.com>> wrote:
> 
>     Yes it is. Thank you very much!
> 
>     On Wed, Oct 4, 2017 at 10:48 PM, Martin Burnicki
>     <martin.burnicki at burnicki.net <mailto:martin.burnicki at burnicki.net>>
>     wrote:
> 
>         ST Intern wrote:
>         > Hi, Understand that it is backward compatible.
>         > I would like to know if Windows 10 ntp version is it NTPv4 specifically,
> 
>         Do you mean, if the w32time service shipped with Windows 10 uses
>         NTP v4
>         protocol?


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