Network acceleration with TCP Fast Open
Getting There Faster
© ndul, 123rf.com
With TCP Fast Open, Google introduces a protocol extension, implemented in the Linux kernel, that avoids unnecessary latency in network traffic and promises up to 41 percent acceleration, depending on the application.
In mid-2011, Google's "Make the web faster" team, which is led by Sivasankar Radhakrishnan, Arvind Jain, Yuchung Cheng, and Jerry Chu, presented a draft for reducing preventable latency. The technique, which is called TCP Fast Open (TFO) [1] [2], depends on streamlining the process of opening a TCP session.
The idea itself is not new – way back in 1994, RFC1379 and RFC1644 [3] [4] specified the conceptually similar Transactional TCP (T/TCP). Unfortunately, an analysis published in September 1996 revealed serious security issues with T/TCP [5], and the technique failed to establish itself on a broader front. Based on this previous experience, the Google team refined the approach when developing TFO, leading to an improved result. Linux kernel 3.6 implements the necessary client-side infrastructure, and 3.7 will include support for TFO on the server end, so it looks like the era of faster TCP connections might be just around the corner.
The Time Thieves
The lion's share of today's Internet traffic is characterized by relatively short-lived data streams. With a website, for example, multiple simultaneous TCP sessions open briefly to transfer a relatively small amount of data comprising many small elements (e.g., HTML code, small graphics, and JavaScript) [6]. Because of the high performance cost associated with repeatedly establishing TCP connections, browsers often try to keep unused connections open after first calling a site (these are known as HTTP persistent connections). But, on high-traffic servers, administrators configure very tight timeout controls to avoid tying up resources unnecessarily. Thus, the time required to open and re-open TCP connections remains a source of performance problems.
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