Hi all,

We just chased two weeks of intermittent inbound RTP loss (carrier toward our SBC, business hours only) that nothing we had could see. Our SBC's counters and VoIPmonitor agreed on what arrived; the carrier's egress probe showed zero loss, so the loss was somewhere on the public path between them, and the carrier called it clean. We are also mid-migration from Metaswitch to NetSapiens, so whatever we set up has to make sense on both.

Before this, we had VoIPmonitor on a mirror of the SBC traffic and Smokeping and LibreNMS watching our own routers, which told us nothing about the carrier path. What we are putting in now: MOS and loss alerts in VoIPmonitor, Smokeping with call-shaped pings (1 per second, 172 bytes, EF) to every hop toward each carrier that answers, and SIP OPTIONS every minute to the carriers' SBCs (they answer with a 500, which is fine; it is a timed reply over the real path). The gap is anything that measures inbound traffic to us continuously.

I am after persistent monitoring people have left running for months, not one-off tests. A few things I would like to hear about:

- Scheduled test calls through the carrier, scored by your passive monitor. Who places them, how often, and did it ever catch something before customers did?

- Carriers that give you ongoing quality data: RTCP from their side, a looking glass, per-trunk stats. Does anyone get this without a fight?

- Measuring one-way loss toward you. A VM near the carrier running irtt or similar? Something a NetSapiens shop already does out of the box?

- OPTIONS to carrier SBCs as a standing probe. Any carrier pushback?

The 2023 "troubleshooting RTP loss" thread covered the one-off side (mtr, sized pings, Telchemy). I will summarize the replies and add them to the list.

Thanks,
Mike