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TCP/IP tuner for improving network performance and compatibility.

IPNetTunerX is a modest application that allows you to optimize TCP/IP network performance under Mac OS X by tuning internal TCP/IP parameters to match your network environment. IPNetTunerX supports over 50 adjustable parameters including the TCP Window Size, Time Out intervals, Maximum Segment Size, and MTU.

Beyond adjusting parameters, IPNetTunerX provides tools for measuring the effect of your changes, and a Location Helper to make dynamic configuration easier.

Use our preconfigured settings for most common types of Internet connections. Or you can adjust your settings and save them in IPNetTunerX settings documents and invoke them automatically each time you login (or at system startup).

While not all connections require tuning, it is often possible to improve network performance significantly by using the right parameters for your connection. IPNetTunerX makes it easy to experiment and see for yourself.

As with all of our Macintosh software products, IPNetTunerX features a fully functional 21 day trial period.

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System Requirements: Mac OS X 10.3.9 or later, Leopard compatible.



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IPNetTunerX must run on each machine on a network to get maximum performance. Take advantage of our Multipack pricing and save!

Why is it Sometimes Necessary To Tune TCP/IP?

  • TCP/IP is not controlled by any manufacturer and is designed to work on almost any kind of underlying network with widely varying characteristics.

  • To meet this challenge, the protocol designers made TCP adaptive. TCP is self monitoring and optimizes its own behavior to match the network environment. Adaptation takes time and the default settings cannot optimize for every possible kind of network.

  • There are many independent implementations, the protocols continue to evolve in response to practical experience, some implementations have peculiar compatibility constraints.

Why can't somebody just write a utility that analyzes my network and automatically selects the optimum settings? Such a tool would be both useful and popular. The answer is they already have, it's called TCP/IP, but sometimes it needs a little help.

In most cases, TCP works remarkably well all by itself. Tuning is needed in those cases where TCP doesn't quite get it right because the network behavior is outside the expected range. Typical problems include:

  • Asymmetric connections that are much faster downstream than upstream.
  • High performance connections with relatively long latency (measured in bytes) such as fiber optic, satellite, or PPP via cellular network.
  • PPPoE (or Cisco VPN) implementations that restrict the network MTU without support for "Path MTU Discovery" or fragmentation.
  • Heavily congested links. Tuning can't solve everything. You may need to restructure your network or use packet shaping to control traffic flows <>.

The key to optimization in such cases is to measure, adjust, repeat. Notice it's not necessary to find the perfect settings, only to get close enough that TCP works efficiently in your environment. The tools included with IPNetTunerX are designed to make this easy and show how well TCP is actually working.

To keep it simple, IPNetTunerX offers a collection of presets to solve the most common tuning problems for users with asymmetric broadband connections.

What if I have more than one kind of network connection, like wireless internet served through a satellite. Which one should I tune for?

Just as a chain is only as strong as its weakest link, you want to tune your connection to improve performance over the weakest link or bottleneck. If the connection is highly asymetric, has MTU restrictions, high latency, or some other problem, you adjust to compensate. "Tuning" can be a little misleading in this case since it suggests tweaking to find just the right setting. "Bottleneck Bypass" is a better description of what you are trying to achieve. Getting around one bottleneck might reduce performance slightly in another area, but this usually isn't a problem.

Can I tune TCP differently for my Ethernet LAN versus Internet connection if they use different network ports? TCP sits above the IP network layer so doesn't normally know how the underlying data will be routed.

Can I tune TCP at my router, or do I need to tune TCP at each host on my LAN? TCP is end-to-end, so it generally makes sense to tune TCP at one or both ends of the connection. Some devices offer "packet shaping" to adjust TCP traffic flows enroute to reduce congestion. Another possibility is to use a proxy server so that external connections originate from a different host. Depending on the problem, these might be appropriate but are generally more involved.

What's New

IPNetTunerX is a completely new implementation in Cocoa for the native Mac OS X networking stack. The included sample tuning documents along with the Link Rate and TCP Rate tools make it easier than ever to test performance and verify the effect of network tuning.


A Location Helper tool allows you to switch settings automatically when your network location in the Network Preferences panel changes, new interfaces come online, or even upon wake from sleep. Simple startup scripts don't provide this. IPNetTunerX can maintain a set network MTU for AirPort Wireless as you move from one network to another. Some PPPoE or VPN connections require a reduced MTU, and IPNetTunerX supports this even when connecting via AirPort.

The Link Rate tool now calculates RTT, Bandwidth-Delay Product, and One Second Window Size making it easy to verify and set the correct TCP Window Size.

The TCP Rate tool shows the effect of parameter changes on the fly including received, sent, duplicate, and retransmit data rates.

Version 1.4 or later adds support for tuning SmallTree Gigabit Ethernet cards using "stegutil". Supports Small Tree's Intel line including Multi-port Gigabit Copper, 10 Gigabit Copper, and 10 Gigabit Optical Ethernet Cards <>. To see the new tuning options, you'll need to download and install the driver for these cards. A new "stegutil" parameter group will appear.

Product Comparison

Compared to other (free) UNIX tools, IPNetTunerX offers the following advantages:

  1. Solves more common tuning problems. Simple presets make it easy to try it and see for youreself.
  2. Experiment with confidence: does not modify any system configuration files; easily restores factory default settings.
  3. Allows you to view and adjust more parameters from a single convenient application. Includes a description of each parameter.
  4. Easily apply network settings for different locations or as new interfaces come online such as AirPort wireless.
  5. Includes tools that let you see how TCP/IP is working in the real world so you can actually measure and verify performance instead of just guessing.
  6. Includes detailed help and technical support.



Click here for the Classic-only version of IPNetTuner