[ntp:questions] Interpretation of Status field in NTP Control Message Headers
bjourne at gmail.com
Wed Nov 12 16:36:05 UTC 2008
I have a question about the Status field in NTP Control Message
Headers. On p.55 of rfc1305 it says:
"Status: This is a 16-bit code indicating the current status of the
system, peer or clock, with values coded as described in following
The rfc then lists four different interpretations of that field;
System Status Word, Peer Status Word, Clock Status Word and Error
Status Word. I C parlance the field is a union. What is not clear to
me is how you can know what field type you have in a particular
p.56 says "The system status word appears in the status field of the
response to a read status or read variables command with a zero
association identifier." So the Status field is a System Status Word
if the association identifier equals 0 AND the operation is either
Read Status or Read Variables.
p.57 says "A peer status word is returned in the status field of a
response to a read status, read variables or write variables command
and appears also in the list of association identifiers and status
words returned by a read status command with a zero association
identifier." That text is somewhat confusing. The Status Field is a
Peer Status Word if the association identifier is not 0 AND the
operation is either Read Status, Read Variables or Write Variables?
p.58 says "As in the read status command, the association identifier
is used to identify which one, zero for the system clock and nonzero
for a peer clock. ... A system or peer clock status word appears in
the status field of the response to a read clock variables or write
clock variables command." I have no idea what that means or in which
circumstances a Clock Status Word is returned in the Status field.
The description of the Error Status Word is much more
straightforward. As long as the E (error bit) and R (response bit) are
set, then the Status is an Error Status Word.
Hopefully someone can shed some light on this.
More information about the questions