Adjusting TCP for high performance

The Pittsburgh Supercomputing Center (PSC) has a nice writeup on their research into adjusting TCP parameters in order to maintain a high throughput on a system.

The article is constantly being updated, and in addition to general principles, provides specific instructions on adjusting the network stack parameters on FreeBSD, Linux, MacOS X, Solaris, Windows XP, and even more! However, despite the broad breadth of converage (including Netware 5 and HP-UX 9 and up) there is no coverage of OpenVMS. This can perhaps be forgiven considering the newness of TCP/IP on OpenVMS.

I’ll be implementing this in FreeBSD on my laptop shortly and I’ll let you know how this goes. HP-UX details and Linux details will follow as I experience them.

2 thoughts on “Adjusting TCP for high performance”

  1. I was pointed at your blog, so felt I should comment…

    Regarding TCP/IP on OpenVMS, you can tune a large variety of parameters via th SYSCONFIG utility. This type of functionality is common to most/(all?) platforms. We (OpenVMS) use the same BSD stack as was available on Tru64 UNIX. After Tru64 UNIX was sidelined, we have continued to actively develop the product with many new features.

    We spend a great deal of effort on providng high-performance network operation, in what is regarded as the most demanding customer-application environments on the planet. In addition, RAS is the fertilizer that feeds all OpenVMS products, including TCP/IP.

    The first TCP/IP kit on VMS (as it was known then) arrived around 1988 (I don’t have a definite reference for now). That’s 20 years ago, and 10 years after the first release of VMS – Yep, OpenVMS turned 30 last Oct. So, I don’t understand the context of your comment “considering the newness of TCP/IP on OpenVMS”.

    For more information on how tune TCP/IP on OpenVMS, go to our current product documentation at:, where you will find the “Tuning and Troubleshooting Guide”

    Best regards and keep blogging.

    OpenVMS TCP/IP Engineering.

  2. Thanks for the reply! It would be interesting if the guys at PSC would add OpenVMS to their “other operating systems” page at least.

    I hadn’t realized that TCP/IP on VMS had been around that long; of course, UNIX TCP/IP is older, but that’s not what I said…. Thanks for the correction!

    PS: I did note the 30th anniversary – and in this very blog. Congratulations!

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