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SIP URI calling enables inbound calls to a SIP username, eliminating the need for a traditional phone number. This feature allows direct communication using SIP addresses in the format [email protected].

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Prerequisites

  • Active SIP connection with credential authentication
  • SIP device or softphone registered with connection credentials
  • Feature enabled on the connection’s inbound settings
SIP URI calling is disabled by default and must be explicitly enabled for each connection.

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SIP URI format

Calls are placed to the SIP username using the standard SIP URI format: 
[email protected]
Username requirements:
  • Must begin with a non-numeric character
  • This restriction prevents number spoofing and unauthorized dialing
Example valid usernames: Example invalid usernames:

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Configuration

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Access control options

Configure SIP URI calling access using one of three modes:
ModeValueDescriptionUse case
DisableddisabledBlocks all SIP URI callsDefault security posture
UnrestrictedunrestrictedAllows calls from anyone on the internetPublic-facing services, customer support lines
InternalinternalAllows calls only from SIP connections within the same Telnyx accountPrivate inter-office communication, internal extensions

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Configure via API

PATCH /v2/ip_connections/ with the sip_uri_calling_preference parameter: 
{
  "sip_uri_calling_preference": "unrestricted"
}
Set to disabled, unrestricted, or internal based on security requirements.

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Making SIP URI calls

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From Telnyx SIP connections

Dial directly to the SIP URI from any registered SIP endpoint: 
INVITE sip:[email protected] SIP/2.0

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From external systems

When configured as unrestricted, external SIP systems can place calls: 
INVITE sip:[email protected] SIP/2.0
From: <sip:[email protected]>

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Receiving SIP URI calls

Configure the SIP endpoint to accept incoming calls:
  1. Register the SIP device using the connection credentials
  2. Enable SIP URI calling with the appropriate access control
  3. Configure the dial plan or routing rules to handle incoming calls
The call will arrive with the From header containing the caller’s SIP URI or phone number.

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Billing

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Identifiable sources

Calls from Telnyx SIP connections use standard rate deck pricing based on the originating connection’s pricing plan.

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Unidentifiable sources

When SIP URI calling is set to unrestricted, calls from external or unidentifiable sources are billed at $0.002/minute to the connection owner.
Monitor usage when enabling unrestricted access to prevent unexpected charges from public internet traffic.

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Security considerations

  1. Username validation: Non-numeric username requirements prevent unauthorized number spoofing
  2. Access control: Use internal mode for private communications within the organization
  3. Rate monitoring: Track call volumes and sources when using unrestricted mode
  4. Authentication: Credential-based connections provide secure endpoint registration

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Troubleshooting

If SIP URI calls fail, verify:
  1. SIP URI calling is enabled on the connection
  2. Username begins with a non-numeric character
  3. Access control mode permits the calling source
  4. SIP endpoint is properly registered with valid credentials
  5. Firewall rules allow SIP traffic to/from Telnyx infrastructure