[PATCH 5/9] ntp: Support NTPv3 protocol version

Peter Meerwald pmeerw at pmeerw.net
Tue Sep 17 08:41:52 PDT 2013

> > When we're sending an NTP packet, the version number is always set to 4.
> > That probably doesn't work very well with a bunch of other NTP servers?
> ntpdate does the same (send requests with v4); 
> I'll check what the spec says...

http://tools.ietf.org/html/rfc2030 (section 5, SNTP Client Operation)

A unicast or anycast client initializes the NTP message header, sends
   the request to the server and strips the time of day from the
   Transmit Timestamp field of the reply. For this purpose, all of the
   NTP header fields shown above can be set to 0, except the first octet
   and (optional) Transmit Timestamp fields. In the first octet, the LI
   field is set to 0 (no warning) and the Mode field is set to 3
   (client). The VN field must agree with the version number of the
   NTP/SNTP server; however, Version 4 servers will also accept previous
   versions. Version 3 (RFC-1305) and Version 2 (RFC-1119) servers
   already accept all previous versions, including Version 1 (RFC-1059).
   Note that Version 0 (RFC-959) is no longer supported by any other

Since there will probably continue to be NTP and SNTP servers of all
   four versions interoperating in the Internet, careful consideration
   should be given to the version used by SNTP Version 4 clients. It is
   recommended that clients use the latest version known to be supported
   by the selected server in the interest of the highest accuracy and
   reliability. SNTP Version 4 clients can interoperate with all
   previous version NTP and SNTP servers, since the header fields used
   by SNTP clients are unchanged. Version 4 servers are required to
   reply in the same version as the request, so the VN field of the
   request also specifies the version of the reply.

so no problem I guess
the packet looks the same also

regards, p.


Peter Meerwald
+43-664-2444418 (mobile)

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