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SIP and networks

SIP trunking, SIP ALG, bandwidth and quality of service: the plumbing under a phone system, and what breaks it.

September 9, 2026

How many SIP trunks do you need?

Channels are sized against overlapping calls, not headcount. The arithmetic, a worked example, and what one channel too few actually costs you.

September 9, 2026

Network settings that break VoIP audio

One-way audio has a direction, and the direction names the fault. NAT timeouts, symmetric RTP, double NAT and QoS, in the order worth checking them.

September 9, 2026

SIP ALG: why to turn it off

SIP ALG rewrites the addresses inside your call setup, and it usually gets some of them wrong. What it does, what it breaks, and where the setting hides.

September 9, 2026

What happens when your internet drops

The call goes silent and nothing is told. What a phone system can and cannot do about an outage, how forward on failure works, and what to arrange beforehand.

September 9, 2026

What is SIP trunking, and do you need it?

A SIP trunk links a phone system you own to the public network. What it replaced, how channels are counted, and why most small offices never buy one.

September 9, 2026

Why your VoIP phone will not register

Credentials, then the network path, then the firewall, then the router's SIP helper, then DNS. What each failure looks like, and how to tell them apart quickly.