Guides
Phone Guides: practical VoIP and telephony reference
Phone Guides explains how business phones, SIP, VoIP networks, numbering, and call quality work in plain language. Start with a topic below, or use the troubleshooting path when a call is failing.
Search by topic, symptom, device, or network context.Find a guide for your situation
Foundations
IP and networking cheat sheet
Decode addresses, ports, services, and the first diagnostic checks.
Networking layers
Map a symptom to the part of the network most likely to explain it.
VoIP protocols
Understand SIP, SDP, RTP, and the protocols around a call.
Voice codecs
Choose and troubleshoot audio codecs with practical trade-offs.
Configure and operate
SIP trunking
Understand the PBX-to-carrier boundary before you configure it.
Dial plans
Make number matching and call routing predictable.
Phone provisioning
Plan repeatable endpoint setup without manual drift.
Voicemail systems
Design greetings, storage, access, and notifications.
Call queues
Configure queue behaviour around service goals and reporting.
Troubleshoot
SIP response codes
Translate registration and call-setup errors into next checks.
SIP registration
Diagnose phones that will not come online or stay online.
NAT and firewall troubleshooting
Trace one-way audio and blocked media.
Packet captures
Capture evidence that explains what the call path did.
QoS and call quality
Measure and improve jitter, loss, latency, and congestion.
Numbering and compliance
International dialing codes
Format international destinations consistently.
E.164 formatting
Normalise numbers for storage, routing, and APIs.
Number portability
Understand porting timing, routing, and verification.
Emergency calling
Plan location, routing, and operational safeguards.
Every article aims to answer one practical question, link to related concepts, and identify standards or operational assumptions that need local verification.