What internet connection a cloud phone system really needs

How much bandwidth a call uses

A standard VoIP call uses roughly 100 kilobits per second in each direction, a little more with overheads and higher-quality codecs. That means even twenty simultaneous calls need only a few megabits each way. Compared with a fibre plan offering hundreds of megabits, phone calls barely register. The question is rarely whether there is enough bandwidth for calls alone, but what else is competing for it at the same moment.

Video meetings are far heavier. A Teams or Zoom video call can use one to several megabits each way per participant, and screen sharing adds more. If your phone system is Teams calling, many of those voice calls may turn into video meetings, so size for that rather than for voice alone. Cloud backups, large file syncs and software updates are the other big consumers, and they tend to grab whatever upload capacity is free.

Sizing for your office

Start by estimating your peak concurrent calls. A ten-person office with a busy receptionist might have four or five calls at once; a call-heavy team might have one per person. Add the number of people likely to be in video meetings at the busiest time, and an allowance for normal web and cloud use. Then compare against your plan's upload speed, because upload is usually the tighter limit on asymmetric plans.

Most small offices on a standard business fibre plan with symmetric or generous upload have plenty of headroom. Offices on older copper broadband, slow fixed wireless or congested shared connections in multi-tenant buildings are where problems appear. If you are moving to VoIP, check your upload speed during a busy afternoon, not once at a quiet time.

If you have several sites, size each one separately. A branch with three staff and a desk phone each needs very little, while head office may carry the reception queue, video meetings and the overnight backup traffic for everyone. Note too that call recording, if stored in the cloud, adds no load at your end because the recording happens at the provider. The only extra traffic comes from staff listening back to recordings or downloading them.

Stability beats speed

Voice tolerates very little interruption. A connection that drops for two seconds every so often is barely noticeable for web browsing but will cut words out of calls or drop them entirely. Fibre is generally far more stable than copper, wireless or satellite, which is why it is the preferred foundation for a cloud phone system. Check your router's logs for disconnections and look at whether calls fail at particular times. If the connection itself is unreliable, adding bandwidth will not help. Fix the underlying problem with your internet provider, or move to a more stable technology if one is available at your address.

What your router and firewall need

The router or firewall at the edge of your network decides which traffic goes first when the connection is busy. A business-grade device can recognise voice traffic and prioritise it over downloads and backups, so calls stay clear even when someone is uploading a large file. Consumer routers supplied free with a plan often lack this or make it hard to configure.

The firewall also needs settings that suit your phone provider, such as allowing their servers and adjusting timeouts. Your provider will publish recommended settings; ask whoever manages your network to apply them. If you have several sites, an SD-WAN setup can route calls over the best available link at each moment.

Backup connections for phones

If your internet stops, cloud desk phones stop too. A second connection from a different network, such as 4G or 5G wireless or a second fibre service, with automatic failover keeps calls flowing. Many business routers can switch over in seconds. Even a modest backup connection carries a surprising number of calls, because voice needs so little bandwidth. As an extra safeguard, configure your phone system to divert calls to mobiles if the office goes offline. Most cloud systems detect that desk phones have disappeared and reroute calls automatically. Test both the failover and the divert before you need them.

Staff working from home

Home workers using softphones depend on their own internet connection, which you do not control. Most home fibre handles calls well, but shared connections with family streaming, weak Wi-Fi in a back bedroom or old copper broadband can cause problems. Ask home-based staff who are on the phone a lot to use a wired connection or sit near the router, and check their upload speed.

Where a staff member's home connection is genuinely poor, options include a business-paid fibre upgrade, a mesh Wi-Fi system, or using the mobile app over 4G or 5G. Write minimum home internet expectations into your remote work policy so everyone knows what is needed before a problem appears on a client call.