Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

I've read that iperf basically tries to send as much information down a connection as quickly as possible reporting on the throughput achieved. This tool is especially useful in determining the volume of data that links between two machines can supply.

is it possible to gather the same results by sending regular data, as in not testing data?

what I'm trying to do is this; sending data in the foreground while in the back ground gather statistics (throughput and jitter).

so can anyone tell me how iperf calculates these two values ?

share|improve this question
add comment

1 Answer

up vote 3 down vote accepted

Is it possible to gather the same results by sending regular data, as in not testing data?

I don't believe so, at least not using iperf. If you can capture the real data with pcap/tcpdump/wireshark, then you should be able to use wireshark to determine the jitter.

I suspect iperf calculates jitter using a formula like is defined in RFC 3550 for the RTP protocol. You would probably need to dig into the source to know for certain.

  If Si is the RTP timestamp from packet i, and Ri is the time of
  arrival in RTP timestamp units for packet i, then for two packets
  i and j, D may be expressed as

     D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si)

  The interarrival jitter SHOULD be calculated continuously as each
  data packet i is received from source SSRC_n, using this
  difference D for that packet and the previous packet i-1 in order
  of arrival (not necessarily in sequence), according to the formula

     J(i) = J(i-1) + (|D(i-1,i)| - J(i-1))/16

  Whenever a reception report is issued, the current value of J is
  sampled.

  The jitter calculation MUST conform to the formula specified here
  in order to allow profile-independent monitors to make valid
  interpretations of reports coming from different implementations.
share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.