Everyday Virtualization

VDI Display Protocols -- Why They're Important

Although there are many critical VDI components to consider in your implementations, the choice of display protocols should never be taken lightly.

• By Rick Vanover
• 05/01/2010

Although there are many critical VDI components to consider in your implementations, the choice of display protocols should never be taken lightly. There are a number of them available, including Windows Remote Desktop Protocol (RDP), Citrix HDX 3D, Red Hat Simple Protocol for Independent Computing Environment (SPICE), Sun Appliance Link Protocol (ALP), Teradici PC-over-IP (PCoIP) and HP Remote Graphics Software (RGS).

The display protocol determines two critical measures: experience and resource usage. The sticking point for many organizations will be various levels of multimedia support. Regardless of VDI status, any organization can have issues with multimedia support. This is true not only in large implementations that push bandwidth limits -- even smaller installations may consume enough bandwidth to push the limits of the display protocol without a bottleneck on the wire.

For most VDI solutions, there's a limited number of compatible display protocols. VMware View is different in that it offers a broad selection of protocols; decision makers have their choice of using RDP, ALP, PCoIP or RGS, as well as enhancements to existing protocols. One example of this is Ericom Blaze, which has an upcoming enhancement to support the VMware View broker using RDP, and is currently in use with standard RDP connections for enhanced performance.

What factors determine which protocol to use? Simply put, it comes down to what level of multimedia support is required. RDP has broad device and broker support for VDI installations, but for demanding multimedia requirements, it may not be the best choice for the user experience. In VDI environments, resource utilization can be somewhat mitigated by increasing server processor compute capacity with potentially minimal gains due to the limits of the protocol.

Today's landscape has protocols designed from the ground up with multimedia session experience as a priority. These protocols include PCoIP, SPICE and HDX 3D. They're architected to deliver multimedia at the highest possible levels compared to traditional protocols such as RDP, ALP and Citrix's Independent Computing Architecture (ICA).

There may be configurable options to designate when multimedia components are rendered. When used with XenDesktop, for example, HDX allows administrators to specify whether endpoints should fetch multimedia resources -- including Flash content -- directly from the endpoint, or make the server do the work. For example, in the case of a VDI implementation that hosts many locations on a WAN, it may not make sense for a VDI session to use a WAN connection to put the fetch and render work on the host for Web-based Flash content. This would be the case if a local Internet connection is available. If the endpoint does not have direct Internet access, then XenDesktop can perform a policy-based configuration that prompts the server to perform the fetch and render.

SPICE offers similar in-band logic that determines, for example, if the endpoint client can provide an optimized experience for any multimedia, given the resources in play. If the endpoint is capable of providing local processing, SPICE will render the graphics command there.

PCoIP integration with VMware View also presents options for designing a VDI installation that uses host or client rendering. The Teradici product line includes hardware display protocol solutions, whereas the View integration is a software implementation.

What's clear is that RDP and ICA are insufficient for robust VDI installations that are expected to deliver an experience equal to that of current client PCs. As a result of this more demanding environment, selecting a display protocol is a critical step, and should be one of the fundamental requirements of an internal VDI proof-of-concept installation. I suggest taking your planning one step further to include limited bandwidth modeling, because VDI is also destined to become the new remote access mechanism. Remember: If a robust display protocol isn't selected, future limitations may begin appearing surprisingly soon.