On Nov 28, 2006, at 6:14 PM, Rich Allen wrote:
the round trip time reported on the G4 Xserve probe (OS 10.2) is
reported
incorrectly. the reported time is 1000 times greater than actual;
ie. 767
msec is reported for 0.767 msec. verified this using ping from
several other
boxes/OSs
IM v4.5.1, probe is "Xserve G4 Probe" that was installed with IM
The RTT of different probes will show deviation because different
probes measure different aspects of behavior. The ping probe should
have the smallest RTT; it just tests network connectivity of a single
packet. The XServe probe and other probes test network connectivity
and server responsiveness. (In some cases, there is a little overhead
within InterMapper itself.) When InterMapper probes an XServe (non-
Intel version), it makes a TCP connection to a specific port. Once
the connection is established, InterMapper issues a request for
information, then awaits the full response. As the response is
returned, InterMapper parses out the fields and populates variables
within the probe. The RTT of the XServe probe is thus the total time
it takes from connection establishment until status determination.
Since IM has to parse the entire response in an Xserve probe, it has
to download all of the data.
When the status is determined varies for different probes. For
example, the status of an HTTP probe is determined when the "string
to match" is found. To measure the time it takes a web server to
*start* returning a page, specify start tag "<html>". To measure the
time it takes the web server to return the entire page, specify the
end tag: "</html>". With larger web pages, you'll see different
response times based on the string to match.
One of my current issues with RTT alarming in 4.5.x is that the
default settings don't reflect differences between probes.
Regards,
Bill Fisher
Dartware,
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