(no subject)
Hello,
I'm working for a company called 21Net where we build a system to
provide Internet access on high speed trains using satellite
connections. We have been using IPerf to evaluate the performance of our
system, in both UDP and TCP. However, of late there are some discussions
regarding how the IPerf tool really works, with respect to the UDP
protocol The forum that can be found on sourceforge is not very active,
so I have taken the liberty to ask the question directly to you guys,
excuse me if this not appropriate. If so, please can you direct me to
another resource whee I might find these answers - aside from the source
itself of course.
If I understand correctly, this is what happens:
a) client sends UDP datastream to Server, with the configured packet
size etc.
b) When all data has been sent, the Server verifies the number of
received packets with the number of packets that the client has sent,
and based on this the performance of the system is determined. Number of
OK packets versus the number of NOK packets (those that did not arrive)
However, regarding this calculation following things are unclear to us:
a) when a packet arrives out of order, it is counted as an OK packet, or
is considered to be NOK ; and
b) is the payload of the sent packets verified or not? In case this
verification is done, I assume that when the CRC on a packet fails, it
is counted as a NOK packet; More specifically, where is this done? I
seems that the iperf code lets all packets pass (also the invalid ones)
and only uses the time stamp of these packets to measure the data
throughput.
c) Are there other factors which make IPerf consider a packet as NOK
aside from the above?
Regards,
Kris.
--
Kris Ceuppens
Tel ++32 15 61 88 74
Mob ++32 476 96 09 21
21Net - Kasteeldreef 5B
3191 Hever Belgium