Whether you are an Exchange admin looking to move to a hosted service like Office 365, are considering a migration from your legacy Exchange infrastructure to Exchange 2010, consolidating servers and/or datacenters, or are just trying to optimize server placement, you will be faced with several challenges regarding your network and just how much bandwidth is enough. While benchmarks and recommended practices have been around for years, most of us who have been in that position just took a swag and rounded up to the next random number, and told our boss we needed bigger pipes. After all, there’s no such thing as too much bandwidth, as long as the costs don’t hit your budget.

But if we want to do a better job of estimating our bandwidth requirements, and we really should, there’s a great new tool from Microsoft available now called the Exchange Client Network Bandwidth Calculator. This calculator is actually an Excel workbook with a number of calculations built-in, that enables you to enter your client values across four distinct user profiles, your mix of these profiles and their Outlook versions by site, and then can give you an accurate assessment of the bandwidth required to support those users. Take that value, and if it is less than the existing bandwidth at a site, you should be good to go. If more, time for a circuit upgrade.

While still officially called a beta, you’ll find that there is some great functionality built-in, and support for a broad range of Microsoft clients. Yes, for now, the supported client profiles only include Microsoft products:

• Outlook 2010, 2007, and 2003
• OWA 2010 and 2007
• Windows Mobile and Windows Phone

but it is still in beta, and the blog post announcing the tool’s availability indicates that more clients will be added eventually. This beta uses new algorithms to better predict client behaviours over a number of different configurations including Outlook client version, whether the client is using online or cached mode, and whether they are using MAPI or Outlook Anywhere. It assumes 100% concurrency, which is the right way to approach any estimate like this; you want the worst case scenario. User profiles are based around four profiles: light, medium, heavy, and email admin very heavy. These values are fixed, but seem to be fair estimates of the users in my environment. Your mileage may vary.

If you have more than twenty sites, you may have to use a couple of iterations to estimate them all, but this is a great place to start, and the calculator provides easy-to-understand values and a graphical representation of your requirements. Stated simply, this is a very valuable tool for anyone looking at the network impact on any change to their Exchange environment.

You can read more about the Exchange Client Network Bandwidth Calculator on the Exchange Team blog here, and you can download the XLSX from here. There is also more detailed documentation on how to use the tool in a DOCX you can download from here.

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