Thanks to all that attended the TechTalk live on August 25th! Almost as many individuals have already watched the recording compared with those that attended live. Could you tell that my favorite part was dissecting the ICA packets?

This WAN Optimization TechTalk session will be repeated for the EMEA audience on October 7th, and all are welcome to attend. So if you missed it the first time, here’s your opportunity to attend live. Alternatively, if you wish to see a replay of the first presentation, it can be accessed here.

During the session, a few people asked about how Citrix policies affect the ICA virtual channels and subsequently QoS via Branch Repeater. Some questions arose regarding whether Branch Repeater will override Citrix policies. Citrix policies can be used to disable specific virtual channels (such as client drive mapping traffic), as well as to control the bandwidth for virtual channels (such as printing). If a specific bandwidth allocation has been designated via Citrix policies, Branch Repeater will not exceed that amount even if more bandwidth is available.

In the session, we covered the minimum requirements for XenApp, XenDesktop, and Branch Repeater in order for ICA to be optimized by default. Those versions are:
• XenApp 5 for Windows Server 2003 HRP4+
• XenApp 5 for Windows Server 2008: Hotfix XAE500W2K8046 (x86) or Hotfix XAE500W2K8x64048 (x64)
• XenApp 6
• XenDesktop 4
• Branch Repeater 5.5 and higher
• Citrix Online plug-in v11.0+ for Windows or Linux 11.1+

If those requirements are not met, then there will be no ICA-specific optimizations or compression, rather the built-in compression in ICA will be used, and only TCP flow control will be applied by Branch Repeater.

A few questions came up regarding session sharing and QoS. To clarify, session sharing is when a user has a Citrix connection open and then accesses another resource on that same XenApp server that has the same or suitable configuration (audio, display, etc.) and then that application is then presented within that pre-existing ICA session. QoS isn’t affected by session sharing because a single ICA session is in use. However multiple sessions are launched when the configuration of subsequent apps is not consistent. So, it is best to always use the same settings for your published applications.

Answers to the remainder of the questions, as well as those generated from the EMEA delivery on October 7th, will be posted to the TechTalk site before mid-October.

Jo Harder, Senior Architect
@joharder