Packets Sent Rate
Per-second rate of RTP packet transmission — reveals traffic shaping, pacing issues, and encoder behavior in real time.
Packets Sent Rate
| Property | Value |
|---|---|
| Key | packets_sent_rate_ps |
| Unit | Packets per second (pps) |
| Type | Gauge |
| Direction | Send |
| RFC | RFC 3550 |
What It Measures
Packets Sent Rate measures how many RTP packets the endpoint transmits per second. It is the instantaneous transmission rate derived from the cumulative Packets Sent counter.
For a standard G.711 audio stream with 20ms packetization, the expected rate is 50 packets per second. For video, the rate depends on frame rate and how many RTP packets each frame requires. This metric lets you see the actual pacing of packet transmission in real time.
Why It Matters
The packet rate reveals transmission behavior that cumulative counters hide:
- Pacing verification — A steady rate matching your codec's expected pps confirms proper encoder operation. Fluctuations indicate pacing problems.
- Traffic shaping detection — If a network device is shaping traffic, you may see the packet rate drop below expected levels periodically.
- Silence suppression visibility — With Voice Activity Detection (VAD) enabled, the packet rate drops during silence periods and resumes during speech. The pattern should be visible in the per-second timeline.
- Encoder health — An encoder that intermittently fails to produce packets shows up as rate drops to zero followed by burst recovery.
How CallMeter Measures It
CallMeter calculates the packet send rate by measuring the number of RTP packets transmitted during each one-second measurement window. This produces a per-second gauge value that fluctuates with actual transmission behavior.
Thresholds
This metric does not have fixed thresholds. Expected values depend on codec configuration:
| Codec | Ptime | Expected Rate |
|---|---|---|
| PCMA / PCMU | 20ms | 50 pps |
| G.722 | 20ms | 50 pps |
| Opus | 20ms | 50 pps |
| Opus | 40ms | 25 pps |
| Video (30fps) | varies | 30-120+ pps |
What Causes Unexpected Values
- Rate below expected — Larger packetization interval than configured, silence suppression active, or traffic shaping in effect.
- Rate above expected — Smaller packetization interval, FEC/redundancy packets being sent, or retransmission mechanisms active.
- Rate drops to zero — Endpoint stopped transmitting. Check for hold, mute, or encoder failure.
- Irregular rate — Bursty transmission pattern indicating the encoder or network stack is batching packets rather than sending them at regular intervals.
How to Fix It
- Compare with expected rate. Your codec and ptime setting determine the expected pps. Deviations indicate a configuration or behavior issue.
- Check the timeline. Use CallMeter's per-second chart to identify patterns — periodic drops (traffic shaping), intermittent zeros (encoder issues), or gradual decline (congestion response).
- Correlate with receive rate. If send rate is normal but Packets Received Rate is lower, packets are being lost in transit.
Related Metrics
- Packets Sent — Cumulative counter this rate is derived from
- Packets Received Rate — Reception counterpart for loss detection
- Send Bitrate — Bandwidth equivalent of this packet rate
- Avg Packet Spacing — Shows the timing between individual packets