ICA hungers for bandwidth
Network managers deploying thin-client networks based on Citrix Systems, Inc.'s ICA protocol had better take a long look at advertised bandwidth consumption claims, especially when it comes to file transfers and data streams that carry dynamic graphics.
Tests conducted by researchers at Tolly Research, which publishes ITclarity, reveal that the Citrix Independent Computing Architecture (ICA) protocol commandeers available bandwidth for the duration of file transfers. Moreover, tests show that ICA protocol grabs excessive bandwidth when running graphics-intensive programs over thin-client sessions.
The results serve as a warning to network architects, CIOs and others basing their network performance assumptions on bandwidth utilization statistics supplied by thin-client vendors, and underscores the need for organizations to validate thin-client bandwidth assumptions before they deploy strategic applications.
"We strongly encourage those deploying thin-client solutions to give careful consideration to bandwidth estimation and network planning, and not simply assume the 20K bit/sec-per-user figure that Citrix advertises as an overall average," says Kevin Flood, chief technology officer (CTO) of Tolly Research.
Flood says his research team conducted tests on all three ICA client types -- a Win32 native client, an Active X client and a Java client. None of the client applications clearly distinguished themselves with respect to bandwidth consumption during process initiation -- meaning initial start-up of the tested applications. Engineers noted that during process initiation, the average bandwidth consumption typically exceeded the 20K bit/sec value advertised by Citrix, in one case reaching 108K bit/sec average and peaking at 331K bit/sec in another.
However, the initiation process only lasted between three and 15 seconds. Therefore, it is not likely that process initiation alone will create meaningful network congestion.
Researchers, however, found that bandwidth utilization spiked during tests of common applications -- Microsoft Word, Excel and Outlook -- during file transfers and when supporting graphically intensive applications. File transfers consumed a majority of the available T1 bandwidth, operating at average rates between 990 and 1,334K bit/sec, depending on the type of ICA client and file being transferred.
Compression for the native Windows client, with the data-compression feature enabled, was essentially the same as the compression of the ActiveX client. The native Windows and ActiveX clients transmitted between 46% and 48% of the file size (including network-layer protocol overhead) when transferring text files. Not surprisingly, transfers of 1-Mbyte compressed files were not as efficient, requiring 115% to 117% for either the Native Win32 or ActiveX client.
Likewise, bandwidth usage soared when viewing dynamic graphics over thin-client sessions. Engineers tested screen-saver programs and Microsoft Internet Explorer when viewing an HTML page with animated GIF illustrations.
Two different screen savers tested averaged bandwidth consumption between 515K bit/sec and 1,270K bit/sec, depending upon the ICA client and the screen saver. Qualitatively, visual performance was fairly consistent for all three clients, though the Java client exhibited more choppiness when updating the displaay than the native or ActiveX clients.
The only consistent trend when running the screen-saver programs was that the Java client had the lowest bandwidth consumption. The Win32 and ActiveX client flip-flopped between the most efficient and the least efficient for the two screen savers tested. Variations of up to 30% of the required bandwidth existed between the most and least efficient clients in both screen-saver cases.
The above information is derived from an ITclarity research track report. For information on how to purchase a subscription to Tolly Research's ITclarity service, click here.
About Tolly Research
Tolly Research, provider of ITclarity, is a technology research firm based in Brielle, N.J., that specializes in testing-based research. Tolly Research provides accurate test results, insightful analysis, and practical recommendations for leading-edge technologies required by network professionals. While many businesses have specific implementation issues, there is a broad base of technology research that is applicable to all organizations. Tolly Research offers a more cost-effective method of gathering data than committing internal resources to tackle each new technology. For more information on Tolly Research, point your browser to www.tollyresearch.com, send e-mail to itclarity@tollyresearch.com or call 732-292-9411.
» posted by ITworld staff
Network World
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