NIKHEF Ping

NIKHEF Ping Code

The files for the Ping Code were obtained after decompressing ping.tar.Z by the following actions:

$ uncompress ping.tar.Z
$ tar –xf ping.tar

The files are stored in ~/home/kishanj/pingdir1 subdirectory

Modification of NIKHEF Ping code

It was found that the NIKHEF ping code had some bugs in calculating the RTT (Round Trip Time) and accumulating the statistical data. The code was then sent back to the author and modified. A new executable "ping2" was created for the modified code.

Features added to NIKHEF Ping

Median & Inter Quartile Range(IQR)

The output of the modified NIKHEF Ping code now gives us the Median & IQR along with Min/Avg/Max for the obtained Round Trip Times.

Percentiles

At the command prompt, a maximum of 2 values of percentiles can be given using the -z and -Z options and the corresponding RTT values will be displayed at the output.

A sample of the output for the modified NIKHEF Ping code is given below

---- EPAPHUS.SLAC.Stanford.EDU (134.79.24.48) PING Statistics ----

8 packets transmitted, 8 packets received, 0% packet loss
round-trip (ms) min/avg/max = 2.40/3.42/4.67 (std = 0.771)
(median = 3.36) (interquartile range = 1.62)
(10 percentile = 2.40) (60 percentile = 3.56)

Series Generation using Poisson's distribution

The original ping code has a timeout [-t] option, wherein the user can specify the time interval between ping packets. This is a constant interval and remains the same between all packets. The modified version has a new feature [-P option] wherein the time intervals between pings are obtained from the series generated using Poisson's distribution.

The formula used is _I-1T_I= -log(U_I) / l

Where:

_I-1T_Iis the time interval between the I-1th and Ith ping
U_Iis a pseudo-random number generated between 0 and 1.
l is the inverse of average time interval.

For e.g.: -

=ping2 -t 2 <host> sends packets at a regular interval of 2 seconds.
ping2 -P 2 <host> sends packets according to Poisson's distribution with a mean of 2 seconds.

More information on Poisson's distribution can be obtained from http://www.slac.stanford.edu/~warrenm/poisson/pois.html

Revised 5 August 1999
URL: http://www-iepm.slac.stanford.edu/monitoring/voip/nikhefping.html
Comments to iepm-l@slac.stanford.edu