Voice Trunking: Size, Connect, and Test a SIP Trunk
Yenra | Prepared October 3, 2026
Guide: https://yenra.com/voice-trunking/

Purpose: agree what a trunk must carry and prove the approved connection.
Instructions: use provider and PBX documentation for actual values. Record
PASS/FAIL/UNKNOWN with a timestamp and test reference. Use owned test numbers;
load and failover tests require an agreed window and authorization.

Provider / service / PBX / SBC versions:
Number inventory / incoming destination / outgoing identity requirements:
Provider meaning of origination and termination:
Authentication method / owner (no secrets):
Signaling transport / service domain / certificates and renewal owner:
Media endpoints / codec / packet interval / DTMF / approved firewall policy:
Concurrent-call allowance / measured peak / planned headroom:
New-call attempts per second / provider CPS allowance:
Bandwidth per direction / access bottleneck / overhead assumptions:
Fallback destination / trigger / recovery process / responsible party:

Acceptance: inbound / outbound / two-way audio / DTMF / transfer:
Approved number-identity checks:
Busy or unanswered behavior:
Authorized capacity test / target / observed result:
Authorized failover test / new versus existing calls / result:
Normal routing restored / baseline call passed:
Unresolved item / owner / deadline:
Acceptance signature and date:

Fictional calculation, IPv4 without options, G.711, 20 ms packets:
160 payload bytes + 40 IP/UDP/RTP bytes = 200 bytes.
200 x 8 x 50 packets/second = 80,000 bit/s per direction per call.
12 calls = 960,000 bit/s per direction, excluding link/tunnel/security overhead.
This is arithmetic for a stated model, not a purchased bandwidth requirement.
A fictional 2 CPS limit concerns call starts, separately from concurrent calls.

Supporting sources (see guide for context):
https://www.twilio.com/docs/sip-trunking
https://www.twilio.com/docs/sip-trunking/cps-trunk-termination
https://www.twilio.com/docs/sip-trunking/scale-and-limits