Desktops in the data center: Thin is in

For companies considering thin-client desktops the range of choices has increased quite a bit in the last few years.

From presentation servers like Citrix to desktop blades, companies can now choose how thin to make their desktops.

One interesting approach I wrote about in a previous article is to use virtual machines in blade servers and the Remote Desktop Protocol (RDP) to deliver thin desktops from the data center. Using this approach you can commingle desktop and server images on the same pool of blade servers, alternating loads based on demand. You get to make the most of the existing servers, increase flexibility and simplify your recovery process since both desktops and servers can be recovered to the same machines in another data center.

One of the caveats of such an approach, at least until recently, was that RDP over the WAN has its own limitations. It is not necessarily the best option for delivery of real-time media such as IPTV and VoIP. Real-time media streams can suffer from jitter and latency-induced quality problems, especially if there are no QoS mechanisms in the network. Thus, when running streaming video in an RDP session you may experience slow frame rates and severe choppiness, for example.

At VMWorld 2008 I saw demos of an interesting workaround for this problem. At least one vendor of thin terminals, Wyse, was demonstrating a thin client with built-in SIP capabilities alongside the RDP. Essentially, the hardware client and the virtual desktop/server on the other end of the WAN use RDP for the keyboard, mouse and screen, and use Session Initiation Protocol (SIP) and Real-Time Protocol (RTP) for the voice or video stream.

By multiplexing the two protocols over IP and controlling the QoS, the thin client was able to stream video and audio without difficulty (at least in a demo setup). Extracting the video and audio and using RTP inside SIP to pass it to the client independently allows the client to prioritize the voice and video packets and control jitter and latency (what SIP/RTP does best).

This also introduces another intriguing possibility: If you look at SIP as a general-purpose SIP, it could conceivably be extended to carry RDP as an additional media stream within. Then, instead of using a proprietary approach to run SIP and RDP in parallel, the desktop session could be delivered with SIP alone carrying voice, video and interactive desktop (RTP and RDP) within a single session.

Clearly, thin desktop technology and operating system virtualization together are generating all kinds of innovation. While most enterprises will use thin desktops for specific applications and use cases (such as contact centers and single-application stations) rather than for all desktops in general, the thin desktop is getting more versatile and flexible.