Prioritize Voice Traffic with QoS

Who this is for: Offices where calls get choppy when the internet is busy.

What goes wrong

• Choppy or robotic audio, or words cutting out, when someone is downloading, uploading files, backing up or streaming.
• Calls sound fine early in the morning and bad in the middle of the day.

Why it happens

Your internet connection is a shared pipe. When it's full, the router sends packets out in whatever order they arrive, and voice has to wait in line behind big downloads.

QoS (Quality of Service) tells the router that voice goes first. Calls only need a little bandwidth, but they need it right away.

How to fix it

1. Sign in to your router or firewall's admin page and find QoS, Traffic Shaping, or Bandwidth Management.
2. Set your real upload and download speeds, a little below what your internet plan delivers (about 85 to 90 percent). QoS only works when the router knows the true size of the pipe. Run a speed test to get the numbers.
3. Give top priority to traffic marked DSCP 46 (also called EF). Cannon VoIP desk phones mark their call audio this way. DSCP is a priority tag inside each packet.
4. Give high priority to traffic marked DSCP 26 (also called AF31). Cannon VoIP desk phones use this for call setup.
5. Also prioritize the desk phones by device (by their IP address or MAC address, the hardware ID on the label), and traffic to and from Cannon VoIP's servers listed on the firewall page. Our mobile and desktop apps don't reliably carry the DSCP tag, because phones, Wi-Fi and internet providers often strip it, so this step covers them.
6. Save and test during your busiest time of day.

Notes for common router types

• On most home and small office routers, QoS is under Advanced or Traffic. Many only let you prioritize by device. Mark the desk phones and the computers that use the app as highest priority.
• On most business firewalls, look under Traffic Shaping, QoS, or SD-WAN. Create a rule that matches DSCP 46 and 26 and puts it in the highest priority queue, then a second rule for the desk phones and Cannon VoIP's servers.
• If your router has "trust DSCP" or "honor DSCP", turn it on so it keeps the tags the desk phones add.

How to tell it worked

• Start a large download or file upload, then make a call. The audio should stay clear.
• Run the free Net Checker while the network is busy.
• Ask staff whether calls still get choppy in the afternoon.

More router settings that affect call quality

• Turn Off SIP ALG
• Set UDP Timeouts to at Least 300 Seconds
• Allow Cannon VoIP Through Your Firewall
• Fix Double NAT (Two Routers in a Row)
• Fix Bufferbloat with Smart Queue Management
• Stop Wi-Fi Band Steering and Roaming from Dropping Calls
• Guest and Isolated Wi-Fi Blocking the App
• DNS and Content Filtering Blocking Cannon VoIP
• VPNs and Security Software Interfering with Calls
• Mesh Wi-Fi Systems and Calls Cutting Out
• Wi-Fi Power Saving Causing Missed Calls
• Mobile Hotspots and Carrier-Grade NAT

See all router settings · What makes call quality good or bad