NEWS FLASH: Web10Gig has launched!
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No further Web100 updates are expected.  The only recent changes have been the IPv6 userland bugfix (version 1.8) and the annotated tcp-kis backport below.

While the national high-performance network infrastructure has grown tremendously both in bandwidth and accessibility, it is still common for applications, hosts, researchers and other users to be unable to take full advantage of this new and improved infrastructure. Without expert attention from network engineers, users are unlikely to achieve even 10 Mbps single stream TCP transfers, despite the fact that the underlying network infrastructure can support data rates of 100Mbps or more. On unloaded networks, this poor performance can be attributed primarily to two factors: host system software (principally TCP) that is optimized for low bandwidth environments, and the lack of effective instrumentation and tools to diagnose performance issues.

The Web100 project was created to address these problems. The first is addressed with automatic TCP buffer tuning. The Web100 work in this area has been merged with main-line Linux kernel, and is contained in recent releases. To address the other problem, we have created a set of TCP instruments, defined in RFC 4898. Prototypes of these instruments were implemented in Linux with the Web100 kernel patch.

Note: Web100 is now several years beyond the end-of-funding. We are still updating the kernel patches to track new Linux versions. A good portion of the user base and developers still monitor the discussion list. The only remaining support for the Web100 project is via the discussion list.

If you want production quality code, please ask your OS vendor to support RFC 4898 in their products.


The Web100 software implements instruments in the Linux TCP/IP stack. It is distributed in two pieces: a kernel patch adding the instruments, and a suite of “userland” libraries and tools for accessing the kernel instrumentation.

Current download quick links

For older versions or more information, please contact Chris Rapier (


Support for Web100 is no longer provided.


Web100 was developed and managed by The Pittsburgh Supercomputing Center through the partnerships of The National Center for Atmospheric Research, The National Center for Supercomputing Applications, Cisco Systems, and The National Science Foundation.

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