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Host-based vs. client-based 'remoting' protocols

Microsoft RDP and Citrix ICA were once remote display protocols, but client software isn't dumb anymore, and RPP and HDX allow for partial "remoting" with some redirection.

For years, we've talked about the relative merits of remote display protocols such as Microsoft RDP or Citrix ICA (now called "HDX"). More recently, these protocols have evolved from "remote display protocols" into "remoting protocols." That subtle difference in terminology represents a pretty big change in the technology.

In the old days -- you know, like 1999 -- Remote Desktop Protocol (RDP) and ICA truly were remote "display" protocols. They took whatever graphical and audio content was being generated on the remote host and transmitted it down to the client. Back then, everything was 100% host-based. In other words, the client software was completely "dumb," and all processing happened on the remote host.

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This was a good thing most for standard business applications, such as word processing and client/server apps, but as more multimedia content came into the business world in the early 2000s, a problem started to emerge. People began to realize that it didn't make sense to process a video in a remote session -- a video that was nicely compressed into an MPG or whatever -- and then to have ICA or RDP re-encode that video on the remote host to be transmitted down to the client.

People wondered, "Wouldn't it be easier to just send the original raw video from the original source directly to the client device?" Such thinking led to the creation of what's now known as "redirection," where certain content types are simply redirected down to the client device for client-based processing instead of being processed and rendered on the remote host.

Client-side redirection means that the client devices aren't as dumb as they used to be. For example, in order for a thin-client device to be able to process videos locally, it must have enough horsepower and the proper coder/decoders installed to be able to decode the video.

The downside to multimedia redirection is that you have a higher client requirement in terms of hardware, software and management, but the upside is you have a much better user experience because the video is running locally on the client instead of trying to be rendered on the remote host and sent down via ICA or RDP.

Over the years, Citrix and Microsoft have added several types of redirection capabilities for multimedia, Flash, audio, DirectX, etc., while VMware has rallied around PC over IP and the "remoting only" capabilities.

So which is better -- full remoting or partial remoting with some redirection? It depends on your perspective. Full remoting's main advantage is that everything is supported on any client device. You don't have to have special clients or to manage codecs or to wait for your vendor to support new capabilities (since everything that shows up on the remote host is sent to the client). The downside is that users might not get the best experience in all situations, and the remote hosts have to do a lot more work.

Partial remoting with some redirection means that some multimedia types will be awesome while other types won't. To get that "awesome" performance, you have to use more powerful client devices with locally-installed codecs that you'll need to manage.

At the end of the day, neither one of these is better -- use whatever makes the most sense for your needs and your environment. Each type of remoting is a trade-off.

Brian Madden is an independent industry analyst and blogger, known throughout the world as an opinionated, supertechnical desktop virtualization expert. He has written several books and more than 1,000 articles about desktop and application virtualization. Madden's blog,, receives millions of visitors per year and is a leading source for conversation, debate and discourse about the application and desktop virtualization industry. He is also the creator of BriForum, the premier independent application delivery technical conference.

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