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Run a test on your Internet bandwidth: Visit www.speedtest.netand run a network bandwidth diagnostic. Keep in mind that every VoIP call that is made you require about 30kbs – 50kbs to sustain quality call metrics. You may need to better understand what applications your business uses that are bandwidth intense.
Optimize your router for superior performance and call quality.Disable any of the following features on the router which may cause poor audio quality:
DoS or DDoS protection - Commonly misinterprets audio as an attack
SPI Firewall ( Stateful Packet Inspection ) - Will drop inbound audio
Content Filtering features
Remove any other VoIP based phone hardware such as a Vonage ATA or routers
Prioritize your voice traffic over your data traffic by enabling Quality of Service on your router.