Telephony monitoring guides
How to tell whether a voice circuit is working, how to measure voice quality, how to calculate an SLA and how to read telephony error codes, with what really happens on a call.
Guides
Your 0800 went down and nobody told you: how to monitor 0800 and IVR
Why an 0800 line goes down without anyone noticing, how to test the 0800 and IVR from outside, what Brazil's SAC rules require and what to do when it stops.
The SAC decree and Anatel's RGC: how to prove your 0800 and IVR were up
What Decree 11,034/2022 and Anatel's RGC (Resolution 765) require of phone support in Brazil, and how to document that your 0800 and IVR stayed up.
Silent calls and one-way audio in VoIP: causes and how to fix them
Why a VoIP call connects with no audio or one-way audio: NAT, SIP ALG, RTP ports, the external IP in the SDP, codecs and SRTP. How to find the cause and fix it.
Voice circuit monitoring: SIP trunks, 0800 and IVR
How to monitor SIP trunks, 0800 numbers and IVRs: ping, SIP OPTIONS, passive capture or a real test call, the retry ladder and the evidence that holds up.
Telephony SLA: how to calculate availability by year and by month
How to calculate the availability SLA for SIP trunks and 0800 numbers, by year and by month: the formula, what 99.9% allows, maintenance and what counts as down.
Voice quality in VoIP: MOS, MOS-LQO and ViSQOL in practice
What MOS means in VoIP, how measured MOS-LQO differs from the E-model's estimate, how much jitter, loss and delay voice can take, and what to do about a low score.
Why an 0800 number won't connect from a mobile phone when it works from a landline
Your 0800 works from a landline but not from a mobile? The common causes, from origin blocking to routing, and how to test each one before you open a ticket.
References and tools
SIP codes
Every SIP response code, with what each one means and how a test call reads it.
Q.850 causes
The telephone network's release causes and the map between them and SIP codes.
SLA calculator
The target as allowed downtime, and the SLA you actually had, for the year and the month.
SIP code lookup
Type the error number and go straight to the explanation.
See it on your own circuits
2N5 prepares the demo with the numbers you choose. Three questions, about a minute.