How do I start troubleshooting outbound call quality issues? I have people telling me that "I'm breaking up" or they don't hear a syllable or two. Sometimes entire words are dropped and the calling party will say "Can you repeat that".

From my end, people I call sound fine and the audio of the other party isn't an issue.

My ATA is in the DMZ with a fixed IP address. My cable ISP is connected to my home gigabit LAN and I get 100 megabit down and 20 megabits up service.

Where do I start trying to troubleshoot these audio problems?