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We're doing some DR scenario planning which will require up to 150 users to RDP into their desktop machines (mainly running Windows XP) over our VPN. We have a 2mbit uncontended internet connection at the moment but there's scope to upgrade this and also to use a secondary SDSL line to give us more bandwidth.

Typical bandwidth figures I've seen suggest to plan for 64kbps per session, which works out to 9.6mbps in total. I'd like to know:

  1. Does anyone have any real-world data which would support these estimates?
  2. Are there any operational 'gotcha's that we need to be aware of?

Thanks!

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I think I've seen 64kbps thrown about before as an approximate figure for a session - but do you also need to consider things such as printing, sending data to and from any session mapped devices like USB drives etc? –  Chris W Jun 22 '09 at 11:59
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6 Answers

Its good your upgrading to 10M (as seen in one of your comments) but one thing I'd also consider is instituting QoS at least on the router/firewall level for your RDP traffic. RDP isn't as touch with bandwidth as it is with latency, something QoS helps with.

We have a 6Mbit connection that was close to saturation between offsite backups and, general traffic and RDP. We noticed by implementing QoS on our firewall (running IPCop for about 150+ users) that RDP issues have almost completely gone away.

Our priority setup is similar to this;

VPN - Highest
RDP - High
SFTP - High
Email - Medium
Web - Low
Everything else - Very Low

Now instead of fighting with everything, RDP only has to deal with VPN and SFTP on priority. It cut down on the random disconnects and slowness to the point where I get complaints once every few months instead of multiple times a day.

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Operational gotcha: file transfer will eat a lot of bandwidth

You might want to consider sending in 256 color if what the users are doing do not need 16bit+ as it will save some bandwidth.

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Thanks - under the circumstances we can be pretty controlling about what we allow people to do so preventing file transfer and limiting the colour space will be a possibility. –  user10316 Jun 22 '09 at 16:42
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This depends of lots of things, including, at least, screen resolution, number of colors, if you use printing, sound, file sharing, ... With 64 kbps you can use a screen resolution of 1280 by 1024 in 65k colors (no sound, printer, file sharing) and it's should work great. Of course it also depend of what are doing users, editing a file with nodepad (small change on screen) will use much less than broswing internet (many change on screen very often).

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The other thing you need to take into account is latency. We have a Wireless connection of 54Mbps that runs about a quarter of a mile, and RDP goes across it. Bandwidth is never a concern, but latency can kill us sometimes. I also agree with the other assertions that what the users are doing also play into this number. If everyone is transferring files, things will slow down.

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I've run RDP sessions to servers over 64K and 128K lines (contending with email and other general network traffic) in the past, and these have generally worked just fine. We also have a number of users - about 5 per site, total 50 or so - using RDP over 512/128 contended (30:1) business ADSL as their primary means of network access, and they are actually the remote users we get the least amount of complaints from. This morning even I was on to my own XP desktop over about a 256K medium/high latency circuit and performance and responsiveness were good; not outstanding, and you certainly wouldn't be fooled into thinking you were at a local desktop, but good all the same. I think you should be pretty good with PCs so long as you bear what everone else has said in mind.

I would be looking to upgrade that 2 meg line too, it's rather small for this day and age.

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We're looking at upgrading the connection. Ironically, it's not caused us problems in normal operations - it's seldom saturated! –  user10316 Jun 22 '09 at 23:29
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Upgrade that connection! I have more than 2 Mb coming to my home. I could not imagine supporting that many users on that little of a connection.

While you can do RDP over a slow connection, it is painful.

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This is a 2Mb, symmetrical, uncontended hyperband service over fibre, so it's not really comparable to a 2MB domestic service. Nevertheless, we've committed to an upgrade to 10Mb now so things should fly. –  user10316 Jun 25 '09 at 11:07
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