Telephony monitoring guides

Guides

• VoIP monitoring tools in Brazil: how to choose

  PRTG, Zabbix, VoIPmonitor, SolarWinds, Site24x7, Sipfront, Klearcom, Cyara and Monitor side by side: what each does, what it doesn't, and when to pick each type.

• 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.

• Failing calls: how to diagnose them by SIP code and Q.850 cause

  Calls failing on a trunk or an 0800? A guide to diagnosing them by SIP code (503, 486, 480, 487, 603) and Q.850 cause (16, 34, 127), with the next step for each.

• How to enforce a carrier SLA with proof

  To claim against a carrier's SLA, bring proof: every outage with time, number, SIP code and Q.850 cause, the availability math and the maintenance subtracted.

• Line-down alerts without false alarms

  How to get line-down alerts by email only when the failure is real: retest before alerting, confirmation and escalation until someone takes over.

• Passive monitoring or active test calls: which to choose for telephony

  Tools such as VoIPmonitor and PRTG analyze traffic and the network; active test calls dial from outside. See what each one sees and when to use each.

• The SAC decree and Anatel's RGC: how to prove your 0800 and IVR were up

  What Decrees 11,034/2022 and 13,135/2026 and Anatel's RGC (Resolution 765) require of phone support in Brazil, and how to document that your 0800 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 and MOS-LQO 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.

• What is synthetic call monitoring

  Synthetic call monitoring means placing real calls on a schedule to 0800 numbers, IVRs and SIP trunks and checking the result. See how it works and when to use it.

• 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.