More than once, the first call we get from a new Skype for Business customer involves bandwidth. Namely, the customer doesn’t have enough of it.

Lack of bandwidth manifests in frustrating ways with Skype for Business: video freezes, abrupt Skype Meeting departures, sudden voice garbling (I’ve heard this called “demon wailing”), and the always-irritating dropped call.

When customers call with these issues, they often think Skype for Business is broken. It’s not…it’s just bandwidth-choked. Additional configuration, or a better Internet connection, and voila! Skype is doing great!

Bandwidth allocation is critical to Skype for Business planning. You’ll need to calculate bandwidth needed for each user before deployment. (You can do it after deployment, but it’s messier. Not recommended.)

What’s the Minimum Bandwidth Needed?

According to Microsoft, the minimum bandwidth requirements for Skype for Business (Server) deployments are:

Provision the network links to support throughput of 65 kilobits per second (Kbps) per audio stream and 500 Kbps per video stream, if they are enabled, during peak usage periods. A two-way audio or video session uses two streams, so a simple audio/phone connection will require 130Kbps to cover each stream. Video will likewise use 1000 Kbps total to carry an upstream and downstream connection.

To cope with unexpected spikes in traffic and increased usage over time, Skype for Business Server media endpoints can adapt to varying network conditions and support three times the throughput for audio and video while still maintaining acceptable quality.

Plan Network Requirements for Skype for Business 2015 – TechNet

For those of us who live in the real world, those are obviously minimum numbers. Day-to-day Skype4B usage needs more available bandwidth to comfortably handle office communications.

Calculating bandwidth requirements is an early step in the Skype for Business (or Office 365) deployment process. Before you calculate though, you’ll need to map out the user requirements. Can’t determine bandwidth for all users, if you don’t know how many users you’ll have on the system!

To determine user requirements, list out all these factors:

  • Number of sites
  • Number of users
  • User types: Desktop, mobile, in-office, remote, audio-primary, video-primary, heavy chat, light chat, administrators, etc.
  • Tools used (Video, Skype Meetings, VoIP, Response Groups/Call Queues, App/Desktop Sharing)
  • Estimated traffic numbers (based on the number of simultaneous users)

Okay, now we have some idea of scope. Let’s start on bandwidth.

Choose your Bandwidth Calculator

I went scavenging for the existing bandwidth calculators. I expected to find one…but I found three! Each serves its own specific purpose, though you can use all of them together to weigh your options.

The numbers I entered are based off existing Skype for Business customers. I changed a few to avoid any risk to their security. As a result, the bandwidth requirements don’t 100% match real-world usage. Just so you’re aware.

Skype for Business Bandwidth Calculator/”The Monster”
First and foremost is the Skype for Business Bandwidth Calculator spreadsheet.
Interactive spreadsheet stepping you through the bandwidth numbers needed.

This thing is a monster. It’s the digital equivalent of an airplane’s cockpit – dozens of switches, all jumping out at you simultaneously.

Make sure you download & read through the User Guide as well. It points out several notable things:

  • Only WAN bandwidth is modeled. LAN bandwidth isn’t factored in.
  • Each Site only has one WAN link in the calculator.
  • A “central Site” is assumed to have a PSTN connection, and hosts either a Skype for Business Server Front End pool, or a Skype for Business Cloud Connector Edition.
  • The calculator doesn’t account for situations where users are using the PSTN at another location (e.g. branch site) for some or all of their calls.
    • This could come about due to a dial plan configuration, or a PSTN failure at the users’ local site. Such a situation tends to happen when a critical failure occurs; make sure you consider those when planning.

I entered 2 central sites and 1 branch site, all on-prem. A 50Mbps Internet connection for the San Francisco Site, and a 5 Mbps connection for Ventura (Oakland is associated to San Francisco). The central Sites have a total of 70 users and 3 administrators; Oakland has 15 users. WAN link speed is 50 Mbps; half of that is allocated to RTC traffic, for experimentation’s sake.

RESULTS: On the Aggregated Results tab, I see that Skype for Business only needs 703 kbps (1%) of the San Francisco WAN link, and 2580 kbps (5%) of the Internet connection. At the Ventura site, it needs 1066 kbps (4%) of the WAN, and 2528 kbps (25%) of the Internet connection.

Skype for Business Bandwidth Calculator

(In reality, it will likely need more bandwidth than that…particularly for smooth video conferencing. But I now have a hard-number baseline for my bandwidth estimates.)

Office 365 Planning Tools
Network Planning and Performance Tuning for Office 365 – Office Support
You’ll find several resources for Office 365 network planning on this page, including tools. No surprise, since O365 is cloud-based and needs plenty of bandwidth to function as fast as native apps.

Spiceworks and TechNet users recommend the Exchange Client Network Bandwidth Calculator for O365 bandwidth planning. This is also a downloadable Excel spreadsheet. It’s dated—the latest Outlook version listed is 2011 for Mac—but it’s much simpler and faster than Skype for Business’ calculator. I didn’t even need a user guide (which is good, because it doesn’t come with one!).

I entered 1 Site, Heavy use, with 5 users on Outlook 2011 for Mac, 35 users for Outlook 2010 Online, and 20 users for OWA 2010. Results?

Office 365 Bandwidth Calculator 1
Less than 1 MBits/sec needed. I think most office connections can do that.

It even gives expected peak usage times too.

Office 365 Bandwidth Calculator 2

Again, this calculator is out of date. But something’s much better than nothing, and the results from this make for an at-a-glance foundation while you’re estimating traffic.

Please consult the best practices and references also listed on the above-linked page. They recommend doing a pilot deployment as a test. We often set up 5 users in Office 365 pilots; it’s enough testing to find and fix any bandwidth issues before site-wide deployment.

Teams Bandwidth Calculator
This is for Microsoft Teams, not Skype for Business. But it’s a much simpler tool than the Skype for Business Bandwidth Calculator. Just enter in some user numbers, choose an expected traffic level for discrete services (such as Conference Video Usage), and hit Calculate. Each row represents one Site.

Teams Bandwidth Calculator 1
Teams Bandwidth Calculator 2

With Teams, my numbers indicate that I’d need 3.566 Mbps. Also quite doable.

An interesting point here: The numbers don’t quite match up, but we see that Teams wants more bandwidth than Skype for Business does. I think this occurs for two reasons:

  1. Teams contains many of Skype for Business’ highest-bandwidth tools – Video, Meetings, and Calls.
  2. Notice that the WAN impact is very small; 0.058 Mbps. Teams uses Internet bandwidth much more than WAN. I believe that’s because Teams interconnects with other Office 365 services in real-time. As such, it needs a higher bandwidth allocation to “keep talking” with Microsoft servers and other client computers.

As such, I find this Teams calculator particularly useful. It’s less specific, but it’s really fast and bone-simple to use. Good way to get the network planning ball rolling.

(Can we get something like this for Skype for Business too? It would save so much time…)

You’ll find the calculator at: https://www.successwithteams.com/BandwidthCalculator

Use Bandwidth Calculators Early & Often in the Skype for Business Deployment Process

One last thing: If you’re wondering about bandwidth requirements for a conference room system? The SmartTech Knowledgebase has kindly posted a detailed answer. Their estimate reflects their own SMART Room System product, of course. But that only lends credence to their 20 Mbps bandwidth requirement. Good to know if you’re equipping a conference room with Skype for Business.

Network bandwidth requirements for SMART Room Systems with Skype for Business – SmartTech

The great thing about calculators like these? You’re not wedded to the first result. Test different numbers of users, activity requirements, etc. Running a half-dozen possibilities gives you more detailed bandwidth projections for the future.

Test several models out. It only takes you a few minutes per calculation (even with “The Monster”). Then you can continue, better-informed, with the deployment process.

How do you prefer to calculate bandwidth requirements? Please comment or email. I’d love to get some more tools for comparison testing, if they’re out there.

How to Calculate the Bandwidth You’ll Need for Skype for Business
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