Solaris Network Performance Tuning : know about TCP window size


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10 Responses

  1. Tushar says:

    Hey Mate,

    One quick update, it seems you forgot to add -get switch after ndd to get parameter value.

    Below command will display the current settings in your machine,
    # /usr/sbin/ndd /dev/tcp tcp_recv_hiwat
    # /usr/sbin/ndd /dev/tcp tcp_xmit_hiwat

  2. Tushar says:

    Thank you chief, 5 star to

  3. Ramdev says:

    @Tushar, awesome.  I have fixed those typos.

  4. Thomas says:


    How do I detect if the tcp buffer is overflowing? Is there anything I can check in netstat ? What are the symptoms?

  5. Thomas says:

    Also, is tcp_max_buf = tcp_xmit_hiwat + tcp_recv_hiwat?

    From your analogy of the parking space, it seems you are saying that the data in the receive and send buffer will go into the space available in the max buffer? How is this so? Can you explain clearly the purpose of tcp_xmit_hiwat and tcp_recv_hiwat?

    • Ramdev says:

      @Thomas –

      I understand you question. And these three different buffers here, it is just one buffer i.e. tcp_max_buf.
      I did changed the description of this parameters, little bit to avoid your confusion.

      tcp_xmit_hiwat ( TCP transmit window size )
      tcp_recv_hiwat ( TCP receive windows size)
      tcp_max_buf ( TCP maximum Buffer size)

      tcp_xmit_hiwat & tcp_recv_hiwat are sizes for transmit and receive windows, which are acting as entrance and exit windows for the tcp_max_buf. hope this helps

  6. pradeep varma.k says:

    Hi i am transferring data from windows machine (vm) to solaris 10 (vm) which is in same network but the uploading speed is very slow can u give me any solution on this

  1. September 16, 2015

    […] Read – Knowing about TCP window size […]

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    […] Read – Knowing about TCP window size […]

  3. September 18, 2015

    […] Read – Tuning TCP window size […]

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