Voice troubleshooting - one-way audio, dead air and long PDD

The three classic media complaints, what usually causes them, and exactly what to send us so the first response is a fix rather than a question.

One-way audio

Signalling completed but RTP is only flowing in one direction - almost always an IP/NAT problem rather than a route problem.

• Check your media IPs and ports are reachable from our media addresses (firewall and NAT rules on your SBC).
• Confirm the codec offered was actually agreed both ways - a transcode mismatch can drop one leg's media.
• If your equipment sits behind NAT, verify it advertises its public media address, not the private one.

Dead air (no audio at all after answer)

Both legs silent usually means RTP is blocked entirely, or the answer came from somewhere that never intended to send media - which can indicate false answer on the far end. If you see dead-air calls with suspiciously uniform durations, read "Suspected false answer supervision (FAS)" and report it as potential fraud rather than a media fault.

Long PDD (post-dial delay)

Some PDD is normal on international routes while the call hunts carriers. Consistently long PDD on one destination is worth reporting - we can check where the delay accumulates and re-groom the route.

What to include in the ticket

1. Called and calling numbers (full E.164), timestamps with timezone, and direction.
2. Three or more example calls - patterns matter more than single calls.
3. Which symptom: one-way (which direction has audio), dead air, or PDD in seconds.
4. Your SIP/RTP capture for one example if you have it - it usually halves the resolution time.

Send via the business ticket form marked for the carrier desk; media faults on live routes are worked as priority incidents.