Virtual Desktops for CAD and BIM: is internet latency a problem?

Virtual Desktops for CAD and BIM: is internet latency a problem?

You’re in the middle of working on a key component when your design application suddenly stutters. The frames freeze, jerk, then jump about - this is the nightmare scenario for any designer!

No CAD or BIM professional should have to wait for their application to load. And this is one of the main reasons that virtual desktops for BIM and CAD remain relatively underutilised. Concern about latency (delays interacting with a machine that’s hundreds of miles away) means that many designers prefer using ‘local’ PCs. While they may be more expensive, you know there won’t be any latency issues when working with the machine under your desk.  

But things are changing and a growing number of design and architecture firms are starting to use the cloud to run their BIM and CAD software. So how serious is the issue of latency for virtual desktops running CAD and BIM? 

A primer in latency

Latency refers to the amount of time it takes for a computer to respond after a user performs an action. When you perform an action on most local computers, the response is almost instantaneous (just a few milliseconds). But if the action first needs to be sent over the internet to a datacenter, this will take more time. 

Thanks to the amazing advances we’ve seen in internet speeds, latency really isn’t an issue for most programs and activities. If you’ve ever used Google Docs, for instance, the words you type on your keyboard appear almost instantly on the screen - even if the machine where the text is actually being stored is hundreds of miles away. 

But things get more complex when it comes to ‘heavy’ applications like Autodesk Revit or Dassaults Solidworks. Lots of screen information is generated and exchanged each time you navigate around the 3D model, which could slow things down. And distance does count here - if you’re just a few miles from the data centre, latency won’t be an issue. But if the information is being sent across oceans and half way round the planet, you would start to notice a lag. 

Parallels with the gaming world

Cloud technology is being used extensively by professionals in many fields. However, using a Microsoft version of Word online to edit a document is simply incomparable to running Autodesk Revit - this software needs much more power. 

But, one area that is comparable is the gaming industry. Just like CAD and BIM, video games have traditionally relied on powerful local computers to be able to run high frame rate software and give users a good experience. 

But that’s changing. Over the last couple of years, a number of big moves into online gaming have been announced by major gaming businesses and startups, including:

  • Google Stadia
  • Nvidia GeForce NOW
  • Xcloud - Xbox Game Pass
  • Amazon Luna
  • Vectordash
  • Boosteroid
  • Shadow PC
  • LiquidSky
  • Maximum Settings and Firepower

The jury is still out about whether it’s actually possible to consistently deliver the gaming experiences people expect online. And, for first-person shooter games, local computers still seem to outperform the cloud. That said, these games are super powerful - they have frame rates of over 60 frames per second and high screen resolutions. For many other games (and indeed Autodesk Revit or Siemens NX), this level of speed and power isn’t really necessary. 

How do I know what my latency is? 

If you’re thinking about using CAD or BIM on virtual desktops, latency is going to be one of the most important considerations for you and your users. If you have low latency, the experience of using the the virtual desktops will be almost identical to using Autodesk Revit or other design application right on your desktop computer. But if the latency is high, the experience will quickly feel intolerable. 

Humans can’t really detect any latency below 13 milliseconds (ms). As long as the delay between a user’s input and the screen’s response is less than 13 thousands of a second, we won’t even know the lag. Delays of 50 ms are still small enough to not impact a gamer’s experience, but once the latency surpasses 100 ms, the experience degrades quickly. 

So, before investing in virtual desktops for CAD and BIM, you should first find how much latency there is between your physical computer (the ‘client’) and the host (a virtual desktop running in a datacenter such as Azure). There are a handful of ways you can test latency. 

First is the Internet Speed Test. Your internet speed is a good starting point to know how fast your connection to the internet really is - you can use the test here. If it turns out you have a very poor connection, no virtual CAD or BIM application is going to run smoothly. However, this kind of test has fairly limited value - it is generic, only telling you about your speed of connection to the internet in general. But if you’re using CAD or BIM on a desktop in a specific data center, this is the latency you really want to find out about. 

If you’re using a virtual desktop, you’ll want to know about the latency between your local machine and the datacenter where the actual Autodesk CAD or BIM software (or any other vendor, for that matter) is running. To do this you need to have a virtual desktop running your CAD or BIM application on services like Azure somewhere.

There are then four methods for testing the latency:

  • Ping

Ping is a simple command for testing the latency between two internet-connected computers. You tell your client machine to send a Ping to the datacenter where your virtual desktop is hosted and it measures how long, in milliseconds, it takes to get a response. 

Learn more here

  • Traceroute

Traceroute can be used in conjunction with Ping. It works by tracking a packet of data between your client machine and its destination. It then tells you how many ‘hops’ the packet makes along the network along the way. It can tell you if there are certain hops where it encounters network congestion - which would explain delays. 

It’s described in more detail here

  • High-speed camera

One clever way of checking latency is to use a high speed camera (hint: your iPhone or Android device has one) to record your interaction with CAD or BIM software locally versus on the virtual desktop. 

This requires you to film yourself performing a simple action in - such as clicking on an object, for example. Your camera should film both your click of the mouse, and the screen. You then use software that can analyse how many milliseconds it takes for your action to lead to a reaction on the screen. 

Next up, you do the exact same test, but using your CAD or BIM software on your virtual desktop. You would do the same filming and action and then use software to analyse how many more milliseconds it takes for the on-screen response to register. You’ll then have a clear measure of latency for your specific situation. 

A full description of how to do this (with a video game) is available here

  • The “seeing is believing” test

A final test is a simple experiment where you ask your users to use their normal CAD or BIM application. For half the users it runs on a virtual desktop in the cloud, for the others it runs on a local machine. Individual users shouldn’t know which set up they’re using. 

Afterwards you interview them to ask if they noticed anything different to their normal usage of the software. In the end, this might be the best test of all, since these are the people who’ll actually be using the software day to day. 

What can I do to reduce latency? 

So, what happens if latency does seem too high to use CAD/BIM in the cloud? Does this mean it’s not right for you? Perhaps - but there are a number of things you can do to improve latency too:

  • Use a cable, instead of WiFi: This plugs you directly into the network and means there are fewer ‘hops’ that each data package must complete. 
  • Change QoS settings in your router: Your router may have a so-called Quality of Service (QoS) setting. This tells the system which kinds of apps or connections you want to prioritise (for example, from Solidworks). This means they’ll always get a higher share of the bandwidth. 
  • Use cable or fiber for your internet connection. You will get much lower latency with fiber (10 - 15 ms) or cable (15 - 27 ms) than if you’re using DSL (24-42 ms)
  • Think about location: Choose the most appropriate Virtual Desktop provider for your location. Their datacenter should be:
    • As close as possible to your client (note: 1000 km in distance adds 5 ms in latency 
    • Close to the Internet PoP (Point of Presence)
  • Coding and protocol can also influence latency, in particularly how fast they code the stream to your client. Also the transport protocol (e.g. Remote Desktop Protocol (RDP) or UDP) can make a difference between 10 - 20 ms. 

CAD and BIM cloud latency can be fixed

There is no doubt that latency is an issue for users when it comes to using GPU intensive applications online - be that CAD, BIM or gaming software. However, as the recent investments in cloud gaming by major industry players have shown, the internet is getting much better at supporting GPU intensive software. 

  • As with any IT investment, the first thing to do is to carry out your own tests to be confident that the technology is right for you. By using the tests described above, you can get a true view of latency and whether it’s going to affect your CAB and BIM users.