If you’re experiencing choppy or lagged calls with your SIP trunking service, you may not have an adequate amount of bandwidth available on your Internet service. Use the below simple equation to work out how much bandwidth is needed to support high-quality calls: 

• Number of Concurrent Calls x 85 kbps = Required Bandwidth 
• Most SIP providers use the G.711 and G.729 codecs, which usually require anywhere from 85 - 100 kbps to handle a single call.