VoIP Troubleshooting Guide: Fix Choppy Audio & Dropped Calls
VoIP is usually the first application to break when a network degrades. Calls run in real time over UDP, so a lost or late packet can't be resent. It's simply missing audio. A connection that handles email, file transfers and web browsing without complaint can still make every call sound broken. That's also why VoIP problems are hard to troubleshoot.