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