VoIP Articles

What a Session Border Controller Does (and When You Actually Need One)

What an SBC is for, the five jobs it performs at the edge of a VoIP network, and an honest assessment of when a PBX with a good firewall is enough.

VoIP Toll Fraud: How Attackers Get In and How to Stop Them

How toll fraud actually works, why the bill lands on you, and the layered controls that limit the damage when an extension is compromised.

Encrypting VoIP: SIP over TLS and SRTP, Configured Properly

Why unencrypted SIP is readable by anyone on the path, how TLS and SRTP each protect a different half of the call, and how to configure both in Asterisk without breaking audio.

SIP Registration Explained: Expiry, Qualify and NAT Keepalives

What REGISTER actually does, why phones drop off after a few minutes, how expiry and qualify interact with NAT timeouts, and how to diagnose registration that will not stay up.

Fax over IP and T.38: Why Fax Breaks on VoIP (and When T.38 Is the Wrong Answer)

Why fax fails over VoIP, what T.38 actually does, and the counterintuitive reason G.711 sometimes beats T.38 — including what happens to ECM at a gateway.

5 Causes of Poor VoIP Call Quality and How to Fix Each One

Choppy audio, echo, one-way calls and robotic voices each have a distinct cause. Here is how to identify which one you have and fix it rather than guessing.

SIP Authentication Explained: 401 vs 403 vs 407, Nonces and Digest Auth

What each SIP authentication response actually means, how digest authentication works, and how to tell a credentials problem from a policy refusal in seconds.

Jitter Buffers Explained: Why VoIP Audio Stutters and How to Tune It

What jitter actually is, how a jitter buffer trades latency for smooth audio, the difference between fixed and adaptive buffers, and how to configure one in Asterisk.

MOS Score Explained: How VoIP Call Quality Is Actually Measured

What Mean Opinion Score means, where the 1-to-5 scale comes from, what counts as an acceptable score, and how MOS is estimated automatically on live calls.

VoIP Codecs Compared: G.711, G.729, G.722 and Opus

A practical comparison of the codecs you will actually meet in VoIP — bandwidth, quality, licensing and when each is the right default.