Trunks Overview
A SIP trunk is a virtual telephone line provided by an Internet Telephony Service Provider (ITSP). Through a SIP trunk, users can make and receive calls over the internet, connecting your Cloud-PBX to the public telephone network.
Key Terminology
Session Initiation Protocol (SIP)
An application-layer communication protocol developed by the IETF for creating, modifying, and terminating multimedia sessions with one or more participants. SIP is the standard protocol for VoIP communications.
Key Features:
- Multimedia session management
- Call setup and teardown
- User location and availability
- Session parameter negotiation
Internet Telephony Service Provider (ITSP)
A provider of VoIP telephone service, also known as a VoIP service provider. ITSPs offer:
- SIP trunking services
- DID/DDI numbers
- Call termination and origination
- PSTN connectivity
Examples: TheVoĉo Trunking, Twilio, Bandwidth, local telecom providers
Direct Inward Dialing (DID) / Direct Dialing In (DDI)
Phone numbers that allow external callers to reach specific extensions or users directly without going through a receptionist or auto-attendant.
Benefits:
- Direct external access to users
- Professional business presence
- Multiple numbers on single trunk
- Local numbers in different regions
Registration vs Peer-based Authentication
Register Trunk
Uses username and password credentials to register with the ITSP. The PBX maintains an active registration with the provider.
Use When: Your ITSP provides SIP credentials and requires registration
Peer Trunk
Uses IP address and port for authentication. No active registration required.
Use When: Your ITSP uses IP-based authentication or you're on the same private network
SIP Trunk Types
Purpose
TheVoĉo Cloud-PBX supports multiple trunk types to accommodate different ITSP configurations and use cases.
SIP Register Trunk
Registration-based SIP trunk that uses username and password for registration with SIP providers.
Characteristics:
- Requires SIP credentials (username/password)
- Maintains active registration
- Requires at least one DID number
- Most common trunk type
Best For:
- Standard ITSP connections
- Hosted VoIP services
- Providers requiring registration
Requirement
This type of trunk requires at least one DID number for inbound call routing.
SIP Peer Trunk
IP-based SIP trunk that uses IP address and port of PBX for authentication.
Peer Trunk (DID Based)
The ITSP routes calls based on DID number.
Configuration:
- Uses PBX IP address
- Routes by DID number
- Requires at least one DID
- No registration needed
Best For:
- ITSPs using DID-based routing
- Direct IP trunking
- High-volume environments
Peer Trunk (Port Based)
The ITSP routes calls based on SIP registration port.
Configuration:
- Routes by SIP port
- No DID required
- Maximum 5 port-based peer trunks
- Unique port per trunk
Best For:
- Multi-trunk setups
- Port-based routing scenarios
- Simple configurations
Peer Trunk (Private Network)
Direct trunk connection when ITSP and PBX are in the same private network.
Configuration:
- Internal IP addressing
- No internet traversal
- Low latency
- High security
Best For:
- Local ITSP connections
- Private network deployments
- Inter-office trunking
SIP Account Trunk
Designed for connection between TheVoĉo Cloud-PBX and other devices. The PBX acts as a VoIP account provider, and other devices register this account to connect.
Use Cases:
- Connect to other PBX systems
- Integration with legacy systems
- Multi-site connectivity
- Third-party device registration
Configuration:
- PBX provides SIP credentials
- Remote device registers to PBX
- Inbound/outbound calling
- Codec negotiation
Example Scenario
Connect a branch office PBX to your main Cloud-PBX, or allow a third-party application to register and make calls through your system.
Trunk Status Indicators
Monitor Your Trunks
Understanding trunk status helps you quickly identify and resolve connectivity issues.
| Status | Meaning | Action Required |
|---|---|---|
| 🔴 Disabled | Trunk is manually disabled | Enable trunk if needed |
| ⚫ Unreachable | Cannot reach ITSP server | Check network connectivity and ITSP status |
| ❌ Registration Failed | Authentication failed | Verify credentials, check IP restrictions |
| 🔒 Authentication Failed | Invalid username/password | Update trunk credentials |
| ⚠️ Transport Type Inconsistent | Protocol mismatch | Match transport type (UDP/TCP/TLS) with ITSP |
| 🚫 Rejected | ITSP rejected connection | Contact ITSP for account status |
| 🔄 Registering | Registration in progress | Wait for completion |
| ✅ Registered | Successfully registered | Trunk is operational |
| ⚪ Unmonitored | No active monitoring | Peer trunk normal state |
| 🟡 Busy | Maximum channels reached | Increase channel limit or add trunk |
Trunk Creation Methods
Create from ITSP Template
TheVoĉo Cloud-PBX includes pre-configured templates for leading ITSPs across the globe.
Advantages:
- Quick and easy setup
- Pre-configured settings
- Tested compatibility
- Reduced configuration errors
Supported ITSPs:
- TheVoĉo Trunking (recommended)
- Major regional providers
- Global VoIP services
Recommended
Use templates when available for faster, error-free setup.
Create General SIP Trunk
Manual configuration for ITSPs without templates.
When to Use:
- ITSP not in template list
- Custom trunk requirements
- Special configuration needed
- Testing new providers
Configuration Options:
- SIP Register Trunk
- SIP Peer Trunk (DID/Port/Private Network)
- SIP Account Trunk
Documentation Required
Gather ITSP documentation with server addresses, ports, protocols, and credentials before starting.
Decision Guide
Use Template When:
- Your ITSP is in the template list
- Standard configuration is sufficient
- Quick setup is priority
- Minimal customization needed
Use General Trunk When:
- ITSP not listed in templates
- Custom requirements exist
- Specific codec/protocol needs
- Advanced configuration required
Best Practice
Always start with a template if available, then customize as needed. Templates provide tested, working configurations.
Quick Setup Guide
Add a Trunk
Create and configure SIP trunks
DIDs/DDIs
Manage phone numbers
Inbound Routes
Configure incoming call routing
Outbound Routes
Set up outgoing call rules
Emergency Numbers
Configure emergency calling
Advanced Settings
Codecs, VoIP settings, and more
Common Trunk Scenarios
Scenario 1: Single ITSP with Multiple DIDs
Configuration:
- One SIP Register Trunk
- Multiple DIDs configured
- Inbound routes per DID
- Single outbound route
Best For: Small to medium businesses with one provider
Scenario 2: Multiple ITSPs for Redundancy
Configuration:
- Two or more SIP Register Trunks
- Failover outbound routing
- Priority-based trunk selection
- Cost-based routing
Best For: Businesses requiring high availability
Scenario 3: Local and International Providers
Configuration:
- Local ITSP for domestic calls
- International ITSP for international calls
- Dial pattern-based routing
- Cost optimization
Best For: Businesses with international calling needs