[ntp:questions] SNTP server + ntpd 4.2.4 client

Danny Mayer mayer at ntp.isc.org
Sun Mar 23 01:47:47 UTC 2008


Harlan Stenn wrote:
>>>> In article <47E51FF4.8030708 at comcast.net>, "Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
> 
> Richard> Danny Mayer wrote:
> 
> Harlan> The problem is one might want to *know* that the SNTP server is
> Harlan> actually talking to a refclock, or more generally, that the SNTP
> Harlan> "instance" is playing by the rules.
> 
> Danny> There is no way to ensure that. Furthermore there is nothing in the
> Danny> protocol which allows you to differentiate between the two. This is
> Danny> really a non-starter.
> 
> What is the "non-starter" Danny?
> 

That there's a way of telling the difference. The RFC only tells you 
want you need to send in the packet. It says nothing about identifying 
the type of server and you have no way of probing it for that answer.

> Richard> I can't say it's worth doing but you could always add some sort of
> Richard> a tag to the NTP packet that says "I am an NTP server" or "I am an
> Richard> SNTP Server with a reference clock" or "I am an SNTP leaf node and
> Richard> I'm not supposed to talk to you"
> 
> It's already been done.  It's called the NTP RFC.  The "stratum" tells you
> this.
> 

The stratum is what the server says it is. Why else would Microsoft have 
   their time servers that claim that they are all stratum 2 servers? 
They are not even NTP servers.

> What difference does it make if somebody blows the stratum code v. somebody
> blows the code to say "believe me when I tell you that I am an NTP server"?

Nothing. That's why you cannot differentiate between them and that's why 
it's a nonstarter.

Danny



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