Notable Replies

  1. Hi Rene,

    I saw that you double the window size to 128000 and 256000 etc, and I know that window size filed on TCP header with size of 16 byte which mean the maximum window size = 65536 bits ( maximum IP packet size ), so how is it possible to double up over than that value ??

  2. Hi Hussein,

    Good question, the window size only has 16 bits so that’s only 65535 bits. However, nowadays we use a scaling factor which allows us to use a 32 bit window size.

    You can see this in the wireshark screenshots of this post:

    I don’t have a post that describes how this exactly works so here’s the RFC for now, it explains it pretty well:



  3. Hi Rene

    On the bandwidth delay product your conversion from ms to second is not correct.
    You converted 1ms to 0.01 seconds, this is not correct.
    1ms =0.001seconds


  4. Hello Vinod

    iperf is a utility that runs on Linux, Unix and Windows operating systems. It is not a command that is actually implemented on a Cisco device itself. In the lesson, the iperf command was implemented on the Client and Server devices, which were PCs.

    I hope this has been helpful!


  5. Hi Lazaros, thank you for your reply.
    I made a bandwith test with differents windows sizes and I get just 3.5Gbps but when I add the -P (number of parralel clients) with different windows size I get 8.6Mbps of bandwidth.

    Now Im more confuse I dont know how many bandwidth does my link really has.iperf-windowssize.pdf (637.5 KB)

Continue the discussion forum.networklessons.com

21 more replies!