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Tests show Microsoft's Terminal Server, RDP hog bandwidth

The latest research from Tolly Research IT Clarity.

By CHARLES BRUNO
IT Clarity, 05/23/2000

Users intent on deploying Microsoft's Terminal Server and Remote Desktop Protocol (RDP) to support thin-client sessions may be surprised to learn the software chews up considerable session bandwidth in certain scenarios.

Numerous tests conducted by ITclarity ^TM researchers reveal that the Terminal Server/RDP tandem did not support Microsoft's bandwidth claim of 6K bit/sec per heavy-user session. In fact, tests show that average users of office applications need at least 10K bit/sec, and in some instances when using Microsoft Word bandwidth usage spikes up to 350K bit/sec.

Such bandwidth inefficiency is bound to have a deleterious effect on application performance.

Researchers tested RDP/Terminal Server sessions as they supported applications traffic from common office programs such as word processing, e-mail and spreadsheets.

RDP sessions required four to six times the average bandwidth of Citrix Independent Computing Architecture sessions when delivering office applications.

"When serving desktop applications like word processors or spreadsheets, we found (Citrix) MetaFrame operated much more efficiently than Terminal Server. In fact, one could make a strong business case for deploying MetaFrame from the perspective of bandwidth efficiency, not even taking additional functionality like heterogeneous client support or load balancing into account," says Kevin Flood, chief technology officer of Tolly Research, which publishes the ITclarity information service.

Researchers conducted the bandwidth consumption tests via both Windows NT servers and Windows 2000 servers. Results show that RDP sessions use up to 40% less bandwidth when office applications are served from a Windows 2000 server than an NT Server 4.0.

In other tests, application performance suffered noticeably when RDP sessions were supported over dial-up data rates of 44K bit/sec, a typical dial-up rate provided by ISPs with 56K bit/sec connections. Researchers conducted the dial-up tests to verify Microsoft marketing claims that the sessions could be supported over a 28.8K bit/sec connection. Engineers observed noticeable degradations in application performance when throughput was limited to 44K bit/sec. Application delays and choppy screen refreshes abounded, and reducing the throughput still further to 28.8K bit/sec would only exacerbate the situation.

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