TLS and SRTP for VoIP security
Understand what TLS protects, what SRTP protects, how certificates affect SIP, and what to verify in an encrypted voice deployment.
Blog
Read the latest Phone Guides articles about VoIP troubleshooting, deployments, firmware, security, and Australian telecommunications.
VoIP monitoring and alerting
Build a practical VoIP monitoring plan using registration health, call setup, RTP quality, capacity, and user-impact signals.
SIP registration troubleshooting
Diagnose phones that fail to register, repeatedly authenticate, show offline status, or lose registration behind NAT.
SIP methods and call flow: INVITE, ACK, BYE, and CANCEL
Follow the main SIP methods and understand the normal sequence for registration, call setup, cancellation, transfer, and teardown.
SIP headers explained: the fields that control a call
Learn what Via, From, To, Contact, Call-ID, CSeq, Route, Record-Route, and Authorization do in a SIP message.
Session border controllers: what an SBC does
Learn how session border controllers secure, normalise, route, and monitor SIP and RTP between phones, PBXs, and carriers.
VoIP phone provisioning: a practical deployment guide
Plan secure, repeatable phone provisioning with identity, configuration files, firmware, VLANs, certificates, and rollback controls.
Number portability: what changes during a VoIP number port
Understand donor and recipient carriers, routing changes, cutover planning, validation, and common failure modes during number porting.
Fax over IP: T.38 and audio passthrough
Understand why fax is difficult over VoIP, how T.38 differs from audio passthrough, and how to troubleshoot failed faxes.
Emergency calling over VoIP
Plan emergency calling for VoIP with accurate locations, routing, callback identity, testing, user guidance, and operational ownership.
E.164 number formatting for VoIP and phone systems
Learn how to store, normalise, validate, display, and route telephone numbers using the international E.164 numbering format.
Packet captures for VoIP troubleshooting
Use a small, repeatable packet-capture method to diagnose SIP failures, missing RTP, DTMF problems, and call-quality symptoms.