Bandwidth Usage

Paulo, bandwidth usage is pretty subjective but based on doingn this a few hundred times I can give some guidelines.  For Application Publishing, not the whole desktop, 20-24 users can typically share a T1 1.54Mbps dedicated connection and about 50-55 users can share a dedicated 4Mbps MPLS Circuit.  If the links are shared with other traffic you'd need QoS to prioritize the traffic over things like SMTP, CIFS and HTTP which are less sensitive to congestion.

To acheive these numbers it's typically required to sacrifice things like multimedia, animation, sound... each additional virtual channel or protocol will consume bandwidth.  If it's impossibe to get enough bandwidth, appliances like Cisco WAAS or Expand Networks can dramatically increase the number of possible user sessions, sometimes by a factor of 10.

Certain studies have shown that the minimum bandwidth for a useable RDP Session is approximately 30Kbps. This is something I however consider to be really a bare minimum. Different types of content can dramatically change the bandwidth requirements. Multimedia redirection is an example of this. This is why we also recommend you do proper load testing.

Having said all this if you really need a ballpark figure, the amount of bandwidth needed per virtual desktop user varies very much, depending on the user workload (the content of the session) and how active the use is. As a starting point, this example has the bandwidth figures of a Windows XP virtual desktop session with the following characteristics (application usage):

Microsoft Word

Open, minimize, and close the application; write random words and numbers; save modifications.

Microsoft Excel

Open, minimize, and close the application; write random numbers; insert and delete columns and rows; copy and paste formulas; save modifications.

Microsoft PowerPoint

Open, minimize, and close the application; conduct a slide show presentation.

Adobe Acrobat Reader

Open, minimize, and close the application; browse pages in a PDF document

Internet Explorer

Open, minimize, and close the application; browse a page.

A key component in the bandwidth usage is vWorkspace Graphics Acceleration, a feature of Quest vWorkspace EOP, which can reduce the amount of bandwidth used by 25-75% when compared to native RDP.

This is from a loadtest with 100 users using normal RDP:

· Peak load on network for: 9,7 Mbps

· Average load over the test run: 7,06 Mbps

· Average bandwidth per (1) user: 70 Kbps

Again, vWorkspace Graphics Acceleration (GA)could give you a bandwidth reduction of anywhere between 25% and 75%.

Even more critical than bandwidth is network latency. Latency, as you will know, is about the time it takes for a packet to travel to the server and back again (roundtrip time). Clients by the very nature of the RDP protocol are dependent on the server responses for their screen updates. Any delay in screen updates impacts the perceived performance for the user. Depending on the application and - even more importantly - what users are willing to put up with, you usually need to stay below a latency of about 250 ms to get acceptable performance.

EOP Xtream has the unique capability to greatly reduce the negative effects that latency has on the user experience.

You also have to remember that latency and bandwidth have a special relationship. Once your bandwidth is saturated, latency soon increases tremendously. Think of this as a highway. When the highway is full of cars chances are that you won’t be able to drive at the maximum speed. You will probably arrive (a lot) later at your destination. Latency occurs everywhere. Transmission and equipment delays typically create latencies that may be as low as 1 ms on Local Area Networks (LAN), and are typically 50–100 ms for US domestic links on Wide Area Networks (WAN). For international links, latencies can range from 100-200 ms, sometimes higher, while multi-hop satellite links can produce delays of over 2,000 ms.

So overall, I would recommend that you do not give you customers hard figures because that really could set the expectations wrong. If you have to, be sure that you are on the safe side. You could better have too much bandwidth than too little. Do a proper load-test to make sure that you have the bandwidth you need!

The numbers I seen for the RDP 7 client with the 2-10Mbps setting for experience is about 121kbps/user....but thats with all audio disabled and no printing usage bandwidth.  

Interesting. What is that 121 number - Peak or average?