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WILS: The Many Faces of TCP

Veno. Hybla. CTCP. HSTCP. Fast TCP. Not familiar with these variants? Read on…

Anyone who’s involved with web application performance – either measuring or addressing – knows there are literally hundreds of RFCs designed to improve the performance of TCP (which in turn, one hopes, improves the performance of HTTP-delivered applications that ultimately rely on TCP).

But what may not be known is that there are a number of variations on the TCP theme; slightly modified versions of the protocol that are designed to improve upon TCP under specific network conditions.


A Burton IT research note (G00218070), “Wireless Performance Issues and Solutions for Mobile Users” published in January 2012 goes into much more detail on these variations. As this is a WILS post, I will keep it short and sweet, and encourage you to read through the aforementioned research note for more details or visit the homepages / RFC details for each variation.

High Speed TCP (HSTCP)

Designed for network conditions exhibiting high error rates or bursty data flows. Especially useful over high-latency links with large TCP receive window sizes.

Document-icon HSTCP RFC 3649

Fast TCP

Developed at Caltech, Fast TCP is similar to HSTCP but exhibits better throughput and faster recovery as errors rates increase. It is patented, and embedded in products from FastSoft.

Document-icon Fast TCP Site at Caltech

Compound TCP (CTCP)

CTCP was developed by Microsoft and included in Windows Vista and Windows Server 2008. It combines principles of HSTCP and Fast TCP and according to the research note provides equivalent performance to HSTCP but without the same impact on normal TCP flows.

Document-icon CTCP Working Draft

TCP Hybla

Designed for high-latency satellite links with large error rates.

Document-iconTCP Hybla Website

TCP Veno

Designed for WLAN and WAN links, TCP Veno tries to determine whether packet loss was caused by random signal variations or congestion, avoiding reducing transmission rates when packet loss is due to noise.

pdf-icon TCP Veno: Solution to TCP over Wireless [presentation]

Interestingly, some of these protocols can actually inhibit performance when used in normal network conditions, which seems to make the case that the ultimate solution to choosing a TCP variation is not to choose only one, but to choose one intelligently on-demand.

WILS: Write It Like Seth. Seth Godin always gets his point across with brevity and wit. WILS is an ATTEMPT TO BE concise about application delivery TOPICS AND just get straight to the point. NO DILLY DALLYING AROUND.

Read the original blog entry...

More Stories By Lori MacVittie

Lori MacVittie is responsible for education and evangelism of application services available across F5’s entire product suite. Her role includes authorship of technical materials and participation in a number of community-based forums and industry standards organizations, among other efforts. MacVittie has extensive programming experience as an application architect, as well as network and systems development and administration expertise. Prior to joining F5, MacVittie was an award-winning Senior Technology Editor at Network Computing Magazine, where she conducted product research and evaluation focused on integration with application and network architectures, and authored articles on a variety of topics aimed at IT professionals. Her most recent area of focus included SOA-related products and architectures. She holds a B.S. in Information and Computing Science from the University of Wisconsin at Green Bay, and an M.S. in Computer Science from Nova Southeastern University.