Don’t miss the network sizing

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Just a reminder from my previous blog entries:

 “The virtual desktop experience must be equally as good as the physical desktop experience for the user.”

Terms and definitions

  • RDP (Remote Desktop Protocol)

A proprietary protocol developed by Microsoft, which provides a user with a graphical interface to another computer. The protocol is an extension of the ITU-T T.128 application sharing protocol.

  • PCoIP (PC over IP)

A proprietary protocol developed by Teradicci and used by VMware. Product conforming to PCoIP is VMware view.

  • ICA (Independent Computing Architecture)

This proprietary protocol is for an application server system, and was designed by Citrix. The protocol lays down a specification for passing data between server and clients, but is not bound to any one platform.  Products conforming to ICA are the Citrix XenApp and XenDesktop products.

  • HDX (High Definition Experience) or ICA with HDX:

HDX is Citrix ICA extended technology, especially to optimize Flash playing, VoIP and webcam, and so on.

  • Inbound Bandwidth

This is the network traffic from the desktop server to the client.

  • Outbound Bandwidth

This is the network traffic from the client to desktop server.

  • TCP layer packet error rate

Packet errors may be lost, duplicate, retransmitted, out of order, or packet handling (acknowledgement, TCP window size) packets in the TCP network stream. TCP layer packet error rates can be different from ICMP layer loss packet error rates recorded by many network health test tools.

  • Latency

Latency is given in milliseconds and is an expression of how much time it takes for a packet of data to go from one designated point to another.

Physical distance is not the only factor causing network latency. Network latency is affected by many factors including physical distance, ISP, routers, gateway, and so on.

  • To determine bandwidth requirement, a test scenario is very important, as shown in the following example.
Test category Test scenario
General Windows Activity Test
  • System logon
  • GUI window and mouse
  • Browsing files
Office Productivity Test
  • Word, Excel, PowerPoint
  • PDF
  • Internet Explorer, other browsers
  •  Emails

All tests include files for text, chart, and pictures.

Multimedia Test


  • HD video (480p media file, 25fps, .mov file)
  • Web media (web media file downloaded from YouTube, .flv file)
  • Interactive flash (Flash file with interactive operations, .swf file)
  • Image viewing (800*600 resolution pictures, .jpg file)
  • Standard media (Standard Media file with 25 fps, .wmv file)


Network Test

Some tools are available on the Internet or you can use specific equipment.

  • Bandwidth
  • Latency
  • Packet loss
  • Influencing factors to user experience
  • For general Windows and office related activities, latency is the most strongly correlated network factor for the user experience:  When latency is high, user experience is poor.
  • For multimedia, latency has a strong correlation, and inbound/outbound bandwidth have weak correlations.
  • For interactive flash activities, latency has a strong correlation and outbound bandwidth has weak correlation.
  • Among all the network related parameters, latency always shows strong correlation with desktop user experience

Important points in starting a virtual desktop project

When you start a virtual desktop project remember the following two points:

  • The choice of protocol to be used always influences the user experience.
  • Network sizing is a very important task in any cloud desktop project and is one of the keys for a good user experience.
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