Expert VoIP and SIP engineering for complex voice platforms
Zypager helps companies troubleshoot, secure and modernise Asterisk, FreeSWITCH, Kamailio, OpenSIPS, RTPengine and contact-centre voice infrastructure.
Prefer email? Send call examples, SIP traces, symptoms or architecture notes and receive a written technical response.
If your voice platform is misbehaving, the answer is usually in the SIP.
Separate signalling problems from media-path problems. Reduce blind guessing in voice incidents.
Signalling completes but media flows one direction — usually NAT or SDP rewriting.
200 OK is received but RTP never establishes between the endpoints.
Carrier routing or trunk identification mismatch on the inbound leg.
Codec or SDP offer the carrier will not accept on the outbound INVITE.
Auth, NAT or transport mismatch stopping devices or trunks registering.
Exposed ports, weak auth and unrestricted premium routes inviting toll fraud.
Specialist help across the whole voice path
From the carrier trunk to the application layer — and every relay and proxy in between.
SIP Trunk Troubleshooting
Inbound and outbound call failures, isolated to the leg that breaks.
RTP / No-Audio Troubleshooting
One-way audio and no audio, separated from signalling.
Asterisk Consulting
Dialplan, PJSIP and ARI that are easier to debug and safer to run.
Kamailio Consulting
SIP edge routing, registrar and dispatcher built to scale.
RTPengine Consulting
Media relay and SRTP/RTP bridging that actually carries audio.
VoIP Security Audit
Close the exposure before it becomes a fraud bill.
Real production telephony, not slideware
Hands-on with the systems that carry live calls.
Written, evidence-based, trace-driven
Provide call examples, SIP traces, configuration snippets and symptoms. You receive clear written findings, likely root causes and practical next steps.
Send the evidence
Call examples with date/time and direction, SIP traces, logs, config snippets and architecture notes.
Receive a written diagnosis
Likely root cause, the failing leg, and the reasoning — separating signalling from media.
Apply the fix together
Practical next steps and configuration recommendations, with follow-up where needed.
ARI, Go, and offline speech-to-text
Beyond SIP troubleshooting, Zypager designs custom voice applications using Asterisk ARI, Go, Vosk and carefully scoped automation — recording transcription, ARI workflows and voicebot architecture.
Close the exposure before it becomes a fraud bill.
Exposed SIP attracts scanning, brute-force and toll fraud. Get a prioritised, written set of fixes covering exposure, authentication, rate limiting, route restrictions and transport security.
Transparent “from” pricing
Final pricing depends on scope, urgency, system complexity and access requirements.
Focused written review of one specific issue.
- One SIP / RTP / ASR problem
- Call example review
- Configuration notes
- Written findings
- Recommended next steps
Asterisk, FreeSWITCH, Kamailio, OpenSIPS, RTPengine or trunk review.
- Architecture review
- Security review
- Routing review
- SIP / RTP risk review
- Written report
For urgent incidents.
- SIP / RTP fault isolation
- Carrier troubleshooting
- Failed inbound / outbound calls
- RTP / no-audio issues
- Written follow-up
Urgent incidents outside normal hours.
- Evening / weekend response
- SIP / RTP fault isolation
- Carrier troubleshooting
- Written follow-up
For ongoing support.
- Written technical support
- Periodic review
- Incident guidance
- Architecture improvements
- SIP / security recommendations
Zypager provides technical consultancy and troubleshooting guidance. No guaranteed fixes — work on live systems may require access, backups and change control.
Building toward omnichannel voice and messaging
Zypager’s current work is focused on senior VoIP/SIP engineering. Long term, the company is exploring a broader omnichannel contact-centre platform combining voice, messaging, campaigns, automation, transcription and AI-assisted workflows.
This is a research and architecture direction — not a ready-made product. It may be discussed as discovery or architecture consulting for selected projects only.
Turn symptoms and SIP traces into a clear diagnosis.
Send the evidence and get a written technical response from a senior VoIP engineer.