This is one of the most common questions we get when figuring out the size of an Internet service for an event. We’ve seen a number of online calculators that claim to be able to do the math for you, but a little understanding can go a long way toward avoiding costly mistakes. Ultimately, the right way to figure it out is to determine the highest amount of traffic you expect you’ll need, and then add a safety factor. So the real question becomes how much traffic to expect your users will utilize at any given time. Let’s walk through a simple example, where an event needs to support a dedicated production support connection, a high definition (HD) live webcast, and a WiFi internet service for a 200 person audience that will be heavy users of bandwidth.
Let’s assume that we know the production crew wants a dedicated 20Mbps service so that they can handle production related tasks like downloading presentations and uploading video files and high resolution photography. The best solution is to assume the production crew will know what they need, so this will mostly be a matter of configuring the network to provide for their needs while protecting the remaining services from being degraded if production attempts to use more than their requested speed. Most of the time, this bandwidth is likely to be under-utilized.
For the HD live webcast, there are a couple possibilities, but the safe bet is to assume it needs 10Mbps. Most streaming software will provide compression of the video file that could allow the transmission to be broadcast over a service as small as 5Mbps, but that also reduces the quality of the video. With little to no compression, an HD video will take up a little over 6Mbps, plus 192Kbps for the embedded audio, plus safety (network overhead) factor of 20% brings us to 7.5Mbps. We’ve never seen an ISP that offers a 7.5Mbps service, so like we said before, assume 10Mbps.
Knowing your audience is the key to allocating the correct bandwidth for them. Heavy usage means that the audience will be online a lot, and will be doing things like streaming live to Facebook and Periscope. We can’t afford to provide each of them with a dedicated 10Mbps connection, but we can assume that they won’t all be online at exactly the same time (unless this is planned as part of the event). Even for an audience heavily using the internet, we generally assume that about 30% will be online simultaneously (which brings us to 60 connections). We can also assume they’ll need around 2.5Mbps each while streaming from mobile devices, and around 1Mbps for basic email, browsing, tweeting and posting. It’s also generally safe to assume no more than 10% of the active users will be live-streaming at any one time, and streaming traffic can be given priority on the network. So, if you figure 6 users (10% of 60) that need 2.5Mbps (15Mbps) and 54 users that need 1Mbps(54Mbps), you can assume the WiFi would max out around 69Mbps.
Adding all this up, we come to a total service size for our network of 100Mbps. That includes 20Mbps for the production, 10Mbps for the HD Live Webcast, and 70Mbps for the WiFi. We can afford to cut it close on the overall size because of the different ways the traffic will be used. Webcast is primarily an outbound connection, so most of the inbound bandwidth wouldn’t be used. Production will likely have periods of heavy use inbound and outbound, but for the majority of the time that bandwidth will be unused and available to the WiFi. The heaviest public WiFi traffic we’ve ever seen stats for at an event was a Google conference in 2011, where an estimated 29% of attendees were actively online during busy sessions, but the majority were just using email. Knowing that, we’re probably estimating high in the previous section, and we’ll have the available bandwidth from Webcast and Production to offset heavy use as needed. That said, it’s better to have it and not need it than it is to need it and not have it.
Overall the main point when figuring these numbers out is to have a good idea of how the service is going to be used before deciding on the size. Modern meetings often rely on internet capabilities as much as they do on electricity, and a single bad experience can cause a very public response. If the meeting planner pushes back on the cost, having these types of calculations in hand lets them know what the effect of a slower service could be on the overall event experience.