Adaptive transport for XenApp and XenDesktop optimizes data transport by leveraging a new Citrix protocol called Enlightened Data Transport (EDT) in preference to TCP whenever possible. Compared to TCP and UDP, EDT delivers a superior user experience on challenging long-haul WAN and Internet connections, dynamically responding to changing network conditions while maintaining high server scalability and efficient use of bandwidth. EDT is built on top of UDP and improves data throughput for all ICA virtual channels, including Thinwire display remoting, file transfer (Client Drive Mapping), printing, multimedia redirection (though we still recommend to use the ‘Audio over UDP real-time transport’ policy, since EDT is a reliable protocol. Setting that policy will effectively pull Audio out of EDT and allow it to run over a separate UDP port with no reliability). When UDP is not available, adaptive transport automatically reverts to TCP.
EDT runs on UDP ports 1494 and 2598.
CGP (therefore Session Reliability) is optional on direct EDT connections between Receiver and VDA (e.g. corporate MPLS), so the VDA could be listening on UDP 1494 only
CGP is required for EDT connections via NetScaler Gateway (VDA would be listening on UDP 2598 and 1494 but effectively using 2598)
This is because of the role Session Reliability plays in the UDP-to-TCP fallback feature, as well as the fact that CGP is used as an authorization protocol via NetScaler (it carries the STA Ticket).
So if you have a NetScaler Gateway, EDT requires you enable Session Reliability, which in turn enables CGP.
Session Reliability is enabled in a Studio policy, and Storefront (Manage NetScaler Gateway > Select your NetScaler > Secure Ticket Authority > “Enable Session Reliability”)
Note: If using the Command Line install for the VDA, then the UDP Ports need to be explicitly opened.
XenDesktopVDASetup.exe /ENABLE_HDX_UDP_PORTS
Not to be confused with pre-existing command line:
/ENABLE_HDX_PORT which only opens Audio/RTP ports