VoIP Network Requirements — Bandwidth, QoS, Firewall, and SIP ALG
Reliable VoIP requires modest bandwidth but consistent network behavior: plan roughly 100 kbps per concurrent call in each direction, prioritize voice traffic with QoS, allow outbound SIP and RTP through the firewall, and disable SIP ALG on the router — the setting responsible for more VoIP faults than any other.
How much bandwidth does VoIP use?
About 87 kbps per call with the standard G.711 codec, including overhead — plan 100 kbps for headroom. A 10-person office rarely exceeds 10 concurrent calls: ~1 Mbps each way, trivial for business broadband. Quality problems are almost never raw bandwidth; they are jitter and packet loss caused by congestion, which QoS addresses.
Should SIP ALG be enabled or disabled?
Disabled. SIP ALG (Application Layer Gateway) rewrites SIP packets in transit and routinely corrupts them, causing one-way audio, dropped registrations, and phantom ringing. Signal's phones traverse NAT correctly on their own. Disable SIP ALG on every router and firewall in the path.
Required connectivity
Traffic | Protocol / Ports | Direction |
|---|---|---|
SIP signaling (TLS) | TCP 5061 | Outbound |
SIP signaling (legacy) | UDP/TCP 5060 | Outbound |
RTP media | UDP 10000–20000 | Outbound (return traffic follows) |
Provisioning | HTTPS 443 | Outbound |
NTP (phone clocks) | UDP 123 | Outbound |
No inbound port-forwarding is required. Phones initiate all connections.
QoS and switching
- Tag voice with DSCP EF (46) and prioritize it on your router's WAN queue.
- Use PoE switches to power desk phones; budget ~5 W per phone (class 2) and check the switch's total PoE budget.
- Keep phones and workstations on separate VLANs where practical; supported phones pass a PC through their second port.
Related articles
Last reviewed August 6, 2026. Still stuck? Contact Signal Support from your portal — include what you expected, what happened instead, and one example phone number or extension.