VoIPBin Documentation
Overview
VoIPBIN’s Trunk system provides the infrastructure for SIP-based voice communication, supporting both outbound calls (trunking) and inbound calls (registration). Trunks connect VoIPBIN to the PSTN and enable SIP endpoints to communicate with external networks.
The Trunk system provides:
SIP trunking for outbound call routing
Registration services for inbound call delivery
Connection between VoIPBIN and external providers
Integration with on-premise PBX systems
Flexible routing through providers
How Trunks Work
The trunk system handles bidirectional call flow between VoIPBIN and external networks.
Trunk Architecture
+-----------------------------------------------------------------------+
| Trunk System |
+-----------------------------------------------------------------------+
+-------------------+
| VoIPBIN |
| Platform |
+--------+----------+
|
+-------------------+-------------------+
| |
v v
+-------------------+ +-------------------+
| Trunking | | Registration |
| (Outbound Calls) | | (Inbound Calls) |
+--------+----------+ +--------+----------+
| |
v v
+-------------------+ +-------------------+
| Providers | | SIP Endpoints |
| (Telnyx, Twilio) | | (Phones, PBX) |
+--------+----------+ +--------+----------+
| |
v v
+-------------------+ +-------------------+
| PSTN | | Registered |
| (Phone Network) | | Devices |
+-------------------+ +-------------------+
Key Components
Trunk: Connection to external SIP provider for outbound calls
Registration: Service for SIP endpoints to receive inbound calls
Provider: External SIP service (Telnyx, Twilio, etc.)
PSTN: Public Switched Telephone Network
Trunking vs Registration
Understanding the difference between these two services is essential.
Comparison
+-----------------------------------------------------------------------+
| Trunking vs Registration |
+-----------------------------------------------------------------------+
TRUNKING (Outbound):
+--------------------------------------------+
| Purpose: Make calls to external numbers |
| Direction: VoIPBIN -> Provider -> PSTN |
| Uses: Provider configuration |
| Example: Call +1-555-123-4567 |
+--------------------------------------------+
REGISTRATION (Inbound):
+--------------------------------------------+
| Purpose: Receive calls on SIP devices |
| Direction: PSTN -> VoIPBIN -> Device |
| Uses: Extension configuration |
| Example: IP phone receives incoming call |
+--------------------------------------------+
When to Use Each
Capability |
Trunking |
Registration |
|---|---|---|
Direction |
Outbound calls |
Inbound calls |
Configuration |
Provider + Route |
Extension |
Endpoint |
External phone number |
SIP device/softphone |
Authentication |
Provider credentials |
Extension credentials |
Outbound Call Flow (Trunking)
Outbound calls route through providers to reach external numbers.
Trunking Flow
VoIPBIN Provider PSTN
| | |
| 1. Initiate call | |
| to +1-555-1234 | |
+---+ | |
| | |
v | |
+-------+ | |
| Route | | |
| Engine| | |
+---+---+ | |
| | |
| 2. Select provider | |
| based on route | |
| | |
| 3. INVITE | |
+------------------------>| |
| | |
| | 4. Route to PSTN |
| +----------------------------->|
| | |
| | 5. 180 Ringing |
| |<----------------------------+
| 6. Ringing | |
|<------------------------+ |
| | |
| | 7. 200 OK (Answer) |
| |<----------------------------+
| 8. Connected | |
|<------------------------+ |
| | |
| Media (RTP) <-------------------------------> |
Inbound Call Flow (Registration)
Inbound calls reach registered SIP devices.
Registration Flow
PSTN VoIPBIN SIP Device
| | |
| 1. Call to VoIPBIN number | |
+----------------------------->| |
| | |
| | 2. Flow execution |
| | (dial extension) |
| +---+ |
| | | |
| | v |
| | +-------+ |
| | |Lookup | |
| | |Reg. | |
| | +---+---+ |
| | | |
| | 3. INVITE to registered IP |
| +----------------------------->|
| | |
| | 4. 180 Ringing |
| |<----------------------------+
| 5. Ringback | |
|<----------------------------+ |
| | |
| | 6. 200 OK |
| |<----------------------------+
| 7. Connected | |
|<----------------------------+ |
| | |
| Media (RTP) <-------------------------------------> |
Trunk Configuration
Configure the trunk system through providers, routes, and extensions.
Provider Configuration (for Trunking)
See Provider Overview for detailed configuration.
$ curl -X POST 'https://api.voipbin.net/v1.0/providers?token=<token>' \
--header 'Content-Type: application/json' \
--data '{
"name": "Primary SIP Provider",
"type": "sip",
"hostname": "sip.provider.com"
}'
Route Configuration (for Trunking)
See Route Overview for detailed configuration.
$ curl -X POST 'https://api.voipbin.net/v1.0/routes?token=<token>' \
--header 'Content-Type: application/json' \
--data '{
"name": "Default Outbound Route",
"provider_id": "provider-uuid-123",
"priority": 1
}'
Extension Configuration (for Registration)
See Extension Overview for detailed configuration.
$ curl -X POST 'https://api.voipbin.net/v1.0/extensions?token=<token>' \
--header 'Content-Type: application/json' \
--data '{
"name": "office-phone",
"username": "office1",
"password": "secure-password"
}'
Complete Setup Example
Set up a complete trunk system for bidirectional calling.
Setup Steps
Step 1: Configure Provider (Outbound)
+--------------------------------------------+
| Provider: "Telnyx Production" |
| Hostname: sip.telnyx.com |
| Type: sip |
+--------------------------------------------+
|
v
Step 2: Configure Route (Outbound)
+--------------------------------------------+
| Route: "Default Route" |
| Provider: Telnyx Production |
| Priority: 1 |
+--------------------------------------------+
|
v
Step 3: Create Extensions (Inbound)
+--------------------------------------------+
| Extension: "office-main" |
| Username: office-main |
| Password: ******** |
+--------------------------------------------+
|
v
Step 4: Register SIP Devices
+--------------------------------------------+
| Device registers to: |
| office-main@{id}.registrar.voipbin.net |
+--------------------------------------------+
|
v
Step 5: Configure Number Flow
+--------------------------------------------+
| Number: +1-555-123-4567 |
| Flow: Dial extension "office-main" |
+--------------------------------------------+
Result:
- Outbound: Make calls via Telnyx
- Inbound: Calls to +1-555-123-4567 ring office phone
Common Scenarios
Scenario 1: Basic Office Phone System
Set up a simple office with outbound and inbound calling.
Configuration:
+--------------------------------------------+
| Provider: Telnyx (for outbound) |
| Route: Default -> Telnyx |
| Extensions: office-1, office-2, office-3 |
| Number: +1-555-OFFICE |
+--------------------------------------------+
Call Flows:
+--------------------------------------------+
| Outbound: Any extension can dial out |
| -> Routes through Telnyx to PSTN |
| |
| Inbound: Calls to +1-555-OFFICE |
| -> IVR: "Press 1 for Sales..." |
| -> Routes to appropriate extension |
+--------------------------------------------+
Scenario 2: Multi-Provider Failover
Configure redundant providers for reliability.
Provider Configuration:
+--------------------------------------------+
| Primary: Telnyx |
| Route Priority: 1 |
| |
| Secondary: Twilio |
| Route Priority: 2 |
| |
| Tertiary: Bandwidth |
| Route Priority: 3 |
+--------------------------------------------+
Failover Behavior:
+--------------------------------------------+
| 1. Try Telnyx first |
| 2. If Telnyx fails (5xx) -> try Twilio |
| 3. If Twilio fails -> try Bandwidth |
| 4. All fail -> return error to caller |
+--------------------------------------------+
Scenario 3: Remote Worker Setup
Enable remote workers with softphones.
Setup:
+--------------------------------------------+
| Extension per worker: |
| - remote-john |
| - remote-jane |
| - remote-bob |
+--------------------------------------------+
Worker Configuration:
+--------------------------------------------+
| Softphone App: Zoiper, Linphone, etc. |
| Server: registrar.voipbin.net |
| Username: remote-john |
| Domain: {customer-id}.registrar.voipbin.net|
+--------------------------------------------+
Benefits:
+--------------------------------------------+
| - Work from anywhere with internet |
| - Same extension travels with worker |
| - Company number for outbound caller ID |
| - Inbound calls reach worker globally |
+--------------------------------------------+
Best Practices
1. Provider Management
Configure at least two providers for failover
Test provider connectivity regularly
Monitor call success rates per provider
Choose providers with coverage in your regions
2. Route Configuration
Set up priority-based routing
Configure failover for all routes
Test failover scenarios periodically
Document routing logic
3. Extension Security
Use strong, unique passwords
Rotate credentials periodically
Monitor for unauthorized registrations
Enable TLS when possible
4. Monitoring
Track call success/failure rates
Monitor provider latency and quality
Set up alerts for registration failures
Review call logs regularly
Troubleshooting
Outbound (Trunking) Issues
Symptom |
Solution |
|---|---|
Calls not connecting |
Check provider is configured; verify route exists; confirm provider credentials |
Wrong provider used |
Review route priorities; check for destination-specific routes |
All providers failing |
Check provider status; verify network connectivity; test each provider independently |
Inbound (Registration) Issues
Symptom |
Solution |
|---|---|
Device not receiving calls |
Verify registration is active; check extension in flow; confirm device is online |
Registration failing |
Check credentials; verify registrar address; confirm firewall allows SIP traffic |
Intermittent registration |
Check NAT settings; enable keep-alives; increase registration expiry |
Audio Issues
Symptom |
Solution |
|---|---|
No audio |
Check RTP ports; verify NAT traversal; confirm media IP is reachable |
One-way audio |
Enable STUN/TURN; check symmetric RTP; verify both endpoints can send/receive |
Poor audio quality |
Check network bandwidth; reduce jitter; consider QoS configuration |