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Frequently Asked Questions

  1. Does IPNetTuner permanently change my Open Transport files?
  2. I use IPNetRouter to share my Internet connection. Do I only need to run IPNetTuner on my IPNetRouter machine OR do I need to also run IPNetTuner on all my client Macs?
  3. I am using a hardware router to share my Internet connection. Can IPNetTuner still help me increase the performance of my Macs behind my hardware router?
  4. What is the difference between a Link Rate test and a TCP Rate test?
  5. Why when I perform a TCP Test against some servers I do not note a performance increase?
  6. Why are the Open Transport default values restored when I wake up my tuned Mac?
  7. I opened one of the preconfigured IPNetTuner files and IPNetTuner quit — what's happening?
  8. How can I easily view the settings in a configuration file?
  9. What parameters should I modify to improve performance with my connection?
  10. How do I set the RWIN value in Open Transport?
  11. What is the default value for the "tcp_RWIN_mss_multiplier" parameter?
  12. Where is the Selective Ack option?

Does IPNetTuner permanently change my Open Transport files?

No. IPNetTuner only modifies Open Transport IP parameters stored in RAM memory. IPNetTuner cannot permanently modify any Open Transport files. If you restart your Mac then all Open Transport settings are reset to their defaults. Alternatively, you can also reset individual parameters using IPNetTuner if you wish.

Most users find a set of settings which work best for them. Then they put a copy (or alias) of this IPNetTuner settings document in their Startup Items folder. This way IPNetTuner is automatically launched when the machine is restarted, the chosen settings are invoked, and IPNetTuner quits.

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I use IPNetRouter to share my Internet connection. Do I only need to run IPNetTuner on my IPNetRouter machine OR do I need to run IPNetTuner on all my client Macs?

You should run IPNetTuner on ALL your Macintoshes (both the IPNetRouter machine and each Macintosh client). When you run TCP Tests on each machine, you will clearly see this.

Open Transport's TCP Parameters influence each and every TCP connection. A router, such as IPNetRouter, only forwards datagrams. It does not modify or have any effect on the reliable end-to-end delivery and receipt of datagrams associated with connection oriented services such as TCP. Hence we must modify the TCP stack of every machine in order to affect the machine's performance.

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I am using a hardware router to share my Internet connection. Can IPNetTuner still help me increase the performance of my Macs behind my hardware router?

Absolutely! As mentioned above, Open Transport's TCP Parameters influence each and every TCP connection. Any router, even a hardware router, only forwards datagrams. It does not modify or have any effect on the reliable end-to-end delivery and receipt of datagrams associated with connection oriented services such as TCP. Hence we must modify the TCP stack of every machine in order to affect the machine's performance.

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What is the difference between a Link Rate test and a TCP Rate test?

Please see our Test descriptions for more information on these two tests and how they differ.

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Why when I perform a TCP Test against some servers I do not note a performance difference between the default OT settings and my tuned OT settings?

The throughput from some servers can be limited by other things other than TCP transport parameters. Specifically:

  • the server may be overloaded (not enough CPU power)
  • the server may be limited by the speed of its Internet connection
  • the page you are downloading (testing) is too small. You should test against a page at least 20 Kbytes if possible.

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Why are the Open Transport default values restored when I wake up my tuned Mac?

Since IPNetTuner only modifies OT parameters in RAM, if Open Transport is reloaded then the parameters modified by IPNetTuner will be reset to default values. This would typically occur if you turn Open Transport on or off or your Mac reloads the networking stacks coming out of sleep mode. If this occurs, you can reload the desired parameters by double-clicking on a saved configuration file containing the appropriate settings.

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I opened a configuration file and IPNetTuner quit &emdash; what's happening?

Although IPNetTuner has quit, the parameters in the configuration file have modified your Mac's Open Transport IP networking settings. The observed behavior occurs if the configuration file was saved with the "Auto Configure" option checked in IPNetTuner.

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How can I easily see the settings in a configuration file?

The easiest method is to open the file in a text editor, such as Simpletext; IPNetTuner documents are really text documents. To see the parameters of "Auto Configure" saved documents directly in IPNetTuner use the "Load Settings" button. If you use the "Open..." file function, the settings will be loaded, made active, and IPNetTuner will automatically quit.

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What parameters should I modify to improve performance with my connection?

There are two parameters which, when modified, seem to show marked download improvements for all types of connections:

tcp_deferred_ack_interval=1
tcp_mss_min=536

Specific Cable/DSL/ADSL Connection Settings:

tcp_rwin_mss_multiplier=36
tcp_dupack_fast_retransmit=4
tcp_mss_def=536
tcp_rexmit_interval_max=2000
tcp_rexmit_interval_min=2000
tcp_rexmit_interval_initial=2000

Specific PPP Analog Modem Connection Settings:

tcp_mss_max=536
tcp_mss_def=536
tcp_rwin_mss_multiplier=6
tcp_rexmit_interval_initial=3000
tcp_rexmit_interval_min=3000
tcp_conn_grace_period=3000

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How do I set the RWIN value in Open Transport?

To set the RWIN value with IPNetTuner, use the "tcp_mss_max" and "tcp_rwin_mss_multiplier" parameters. The product of these two values is the maximum RWIN size. For example, if the "tcp_mss_max" value is 2048 bytes and the other parameter is 16, the RWIN size would be

16 * 2048 bytes = 32768 bytes

The proper settings for either parameter can vary depending on the unique properties of your network connection and the remote site(s) you are tuning performance with. See the IPNetTuner documentation for more information.

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What is the default value for the "tcp_RWIN_mss_multiplier" parameter?

It is 0 (zero). This actually results in a RWIN size of about 16K (zero is a special case defined by Open Transport).

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Where is the Selective Ack option?

According to one of Apple's senior Open Transport engineers, Open Transport (all versions) does not support selective ack. If you have information from a non-Apple web site that indicates that Open Transport does support selective ack, please request the webmaster of that site confirm the information with Apple.

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