BYO SIP trunks — Zadarma, Twilio, Bandwidth and custom

Why BYO trunk

SIVO is not a telco. You choose your carrier and pay them directly: per-minute rate, numbers, portability. We just talk SIP to them. Wins:

• No markup on PSTN minutes — you pay your carrier's wholesale rate.
• Number portability stays with your carrier — you don't move them to us.
• Carrier SLA independent from ours (stackable, not coupled).
• Regional compliance — pick the carrier in your jurisdiction (EU vs US vs UK vs LATAM).

Certified carriers

Zadarma 🇪🇸 / 🇪🇺

• Production trunk from day 1. SIVO template with every parameter.
• SIP registration: sip.zadarma.com · sending IPs: 185.45.152.0/24 range.
• DTMF: RFC 2833. Codecs: PCMU, PCMA, Opus.
• DIDs in 100+ countries, competitive EU rates.

Twilio 🇺🇸 / global

• Twilio Elastic SIP Trunking. Supports IP-based or credential-based auth.
• Origination URI: <your-trunk>.pstn.twilio.com.
• Event webhook on the Twilio side if you want cross-telemetry.
• High-quality end-to-end Opus audio with typical MOS > 4.2.

Bandwidth 🇺🇸

• SIP trunk + USA DIDs with native E911 compliance.
• BYO numbers with standard FCC portability.
• Ideal for regulated USA enterprises.

Custom template

Any carrier that speaks SIP (UDP/TCP/TLS) works with the "custom" template. You need:

• Carrier SIP host (registrar or fixed IP).
• Credentials (user + password) or list of authorized IPs.
• Transport (UDP / TCP / TLS).
• Supported codecs (we order preference).
• Source IP range to whitelist in ACL.

Trunk failover

Define a primary trunk and one or more failovers. If the primary doesn't respond in 5 seconds (no 18x, no 200), SIVO retries via the next. Useful for geographic resilience or when combining carriers (one cheap, one premium).

Dynamic ACL

Each trunk carries its allowed_cidrs list. SIVO synthesizes an ACL in FreeSWITCH that only accepts INVITE/REGISTER from those IPs. Generic SIP bots dropped at the network level before touching the DB — massive savings on junk events.

Outbound caller ID

Each agent can have multiple DIDs assigned as selectable caller ID in their softphone. Useful for BPOs calling for multiple brands, sales reps wanting to show a local-country number to the lead, etc. Documented at → SIP trunks guide.