SIP interface

The SIP interface is not described by the companion OpenAPI specification — it is a signalling contract established during onboarding. This page is its reference. See known issues 2–4 for current limitations.

Once an Experience Connection is ACTIVE and an Assignment is in place, Alianza routes inbound calls dialled to the assigned phone number to your SIP endpoint via a Twilio SIP trunk. All SIP sessions conform to RFC 3261.

The call flows and transfer mechanism described in this section assume your Virtual Agent is built on Twilio. This reflects the current supported integration pattern. Support for alternative SIP infrastructure may be added in a future release.

Properties

  • Single origin. Your endpoint only needs to accept SIP traffic from Alianza's outbound IP addresses, provided during onboarding.
  • TLS signalling. All SIP is transported over TLS on port 5061.
  • Per-number enablement. Calls are routed only for phone numbers assigned to your Experience.
  • Failure mode. If your endpoint is unreachable, the call fails — there is no retry or fallback.

Network and transport

Item Detail
Signaling transport TLS. Alianza outbound IP addresses are provided during onboarding for firewall/allowlist configuration.
Media transport SRTP.
Port Configurable. Default 5061 for TLS.
Authentication SIP digest authentication. Alianza will present credentials negotiated during onboarding. IP allowlisting is also recommended.
Failover On timeout or 503, Alianza tries up to seven additional resolved targets. The underlying call is affected if your endpoint is unreachable — see Known Issues.
Caller ID Alianza passes through caller ID via From header / P-Asserted-Identity. Their format and accuracy are not guaranteed.

Allowlisting: Alianza will provide its outbound source IPs during onboarding. Allowlist these on your endpoint's firewall or load balancer.

Authentication: Alianza presents digest credentials on the inbound INVITE. Pair this with IP allowlisting at your edge for defense in depth.

No trunk health checks. Alianza does not check the Twilio trunk before routing a call. If the INVITE to or from Twilio fails, Alianza rejects the call — no fallback re-routing to the business is attempted.

Sub-pages

See also

  • Known issues — current limitations including no health checks on the Twilio trunk and no failover for unreachable endpoints.