13 min read
SIP response codes explained: the complete reference with causes and fixes
SIP response codes from 1xx to 6xx with RFC 3261 meanings, the real causes of 401, 403, 480, 488 and 503, and how to fix each one.
VoIP
Posts about VoIP, newest first.
11 min read
SIP trunks, hosted PBX and softphones: VoIP basics for small businesses
SIP trunk vs hosted PBX vs softphone for small businesses: what each one is, how they connect, what drives the cost and how to choose.
10 min read
VoIP codecs compared: Opus vs G.711 vs G.722 vs G.729
VoIP codecs compared: Opus, G.711, G.722 and G.729 by bitrate and bandwidth per call with RTP overhead, licensing, packet loss and Asterisk codec order.
11 min read
One-way audio or no audio on VoIP calls: causes and step-by-step fixes
Fix one-way or no audio on VoIP calls by checking SDP addresses, SIP ALG, blocked RTP ports, symmetric RTP, codecs and hold, with captures and Asterisk fixes.
10 min read
Zoiper alternatives in 2026: SIP softphones for Android, desktop and Linux
Zoiper alternatives in 2026 compared by platform: Linphone, MicroSIP, Bria, Groundwire, Jami, Telephone and Blink for Android, Windows, macOS and Linux.