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My question and situation is similar to Recommended Connection Speed for Remote Desktop question but I need a little more info.

I know that lag can be a factor in working on remote desktop. Lets ignore that. My question is about is the ideal data rate for a good remote desktop connection.

Assume that my RDP is 1080p display. I am using external monitor that is 1080p as well.

The number of pixels in 1080p are

1920 * 1080 = 2,073,600 pixels.

Each pixel uses 16bits of color (2 Byte). Thus the number of bytes used by one screen is

(2,073,600 bit ) * 2 Bytes = 4,147,200 Bytes or ~ 4MB

Since the screen is refreshed at least 10 times a second (lets assume 10 here), the refresh rate required for smooth connection would be = 4MB*10 = 40 MB/Sec

Does these numbers make sense? Does RDP uses something better than this because that is a lot of bandwidth?

Does the size of monitor at RDP end make a difference at the connection? Bigger monitor takes more bandwidth than smaller one?

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You need to consider data compression on the raw data. For example, I just saved a screenshot of my desktop [1920x1080] to a PNG using Paint.NET and the file was just 148kB. –  TheTurkey Oct 7 '13 at 12:52
    
Good point @TheTurkey. I just tested updating small window vs full window and there is a difference between updating the two. –  Dave Oct 7 '13 at 13:14
    
To be honest, I don't know enough about this subject to provide an answer. Personally, I would expect there to be an 'only refresh what's changed' policy, with a full refresh every 10 or so frames - as happens with digital TV. I would also expect the frame rate to be more like 3-4 fps. But these are just my suspicions; sorry I can't answer your question directly. –  TheTurkey Oct 7 '13 at 15:25
    
@TheTurkey what I found so far, page is refreshed on demand only. If content does not change, page is not refreshed. Of course the monitor itself refreshes the screen at 60 fps. The problem I found the most is when using browser. I found that browser data is sent in jpg chunks as I see fragments get populated. If it was text, rendering will be really fast. That is why RDP is really slow. –  Dave Oct 7 '13 at 17:23
    
To add to what @TheTurkey said, RDP is also a DELTA protocol, its not whole screen refreshes, but small bits of the screen are updates if the change. It also does copy rects, if you move a window it will copy the window's rectangle to the new location and update the newly revealed area behind it –  EkriirkE Jun 8 '14 at 5:38

2 Answers 2

In Remote Desktop Connection (RDP), The Server does not actually sends the screen to the client screen. That process is quite expensive as you have to constantly poll the screen for any changes which can be easily +7MB of data. RDP uses special protocol. It basically uses virtual screen. It kind of interacts with the graphic card. In stead of sending screen to the actual one, it send screen content to a virtual screen.

This article and this by by Nadim Abdo of Microsoft explains it very well. It talks about all the myths about RDP. The following is an bandwidth graph from the article

enter image description here

Typical high bandwidth of RDP is 130 Kbps (Kilo bits per second) Typical low bandwith of RDP such as scrolling etc is about 5kbps.

Note that my problem is mostly with scrolling and switching tabs in firefox. Since I have 4Mbps speed (3.6Mbps effective), this should not be a problem. I am assuming the slow speed that I am getting is because of my server computer which at times does get slow and I know is not the fastest machine on the planet.

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The full screen is not refreshed every 10 seconds. The speed of remote desktop responses will depend on the graphics settings, local devices brought over, whether printers are local or remote, audio settings, and many other factors.

But the bottom line is that the "ideal" speed for remote desktop is "as fast as you can afford".

I agree with you that the biggest issue is often with the browser, but most often I see that if the browser opens a page with an animated graphics file or flash video. I'd suggest that if you plan to use a browser when in an RDP session, disable the display of animated graphics, and perhaps even disable flash.

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