Improving ASR and ACD on non-CLI traffic

ASR and ACD, defined

• ASR (Answer Seizure Ratio) — percentage of calls that get answered.
• ACD (Average Call Duration) — mean length of answered calls.

Both are visible per-route on the VoIP Routes page.

What moves ASR

1. Prefix targeting. A country-level rate is an average. Hitting a specific mobile prefix (e.g. UK 447) routes through the cleanest carrier for that range.
2. Time of day. Answer rates in EU/US destinations peak 10:00–20:00 local. Dialing at 03:00 local tanks ASR regardless of route quality.
3. CLI presentation. On non-CLI routes, presenting a local-looking number (even if it's randomized upstream) improves pickup in some markets.
4. Pacing. Hammering 30 CPS at one prefix triggers carrier-side rate limits. Spread across destinations.

What moves ACD

• Audio quality. g729 is cheap but lossy; ulaw/alaw sound better and keep callees on the line.
• One-way audio. Almost always a NAT issue on your side. Check rtp_symmetric and external IP settings.
• PDD (post-dial delay). If callees hear silence for more than 5 seconds, many hang up. Use progressinband=yes in Asterisk.

When to switch routes

If a route's ASR drops 20% from its published average for 24h, contact NOC. We rotate upstream carriers per destination and can move your trunk to a fresher path.