SIP Trunk Authentication Failure: 407 Proxy Authentication Required on Outbound Calls

Voice & Telephony
1 
HTTP/1.1 407 Proxy Authentication Required
Proxy-Authenticate: Digest realm="genesys-cloud.com", nonce="..."
Content-Length: 0

Our AppFoundry integration is currently experiencing intermittent authentication failures when attempting to establish outbound SIP calls through a configured Genesys Cloud SIP trunk. The application is deployed in a multi-tenant architecture and utilizes the Genesys Cloud Platform API to dynamically provision trunk settings based on customer onboarding events.

The issue manifests specifically during the initial registration phase of the SIP dialog. While the internal application logs confirm that the correct credentials (User Name and Secret) are being passed to the underlying SIP stack, the Genesys Cloud edge consistently returns a 407 Proxy Authentication Required response. This is particularly confusing because the same credentials function correctly when tested directly through the Genesys Cloud Admin console’s “Test Trunk” feature.

We have verified the following configuration parameters:

  • Trunk Type: SIP Trunk (Outbound Only)
  • Authentication Method: Digest
  • Transport: TCP
  • Region: us-east-1
  • API Version: v2 (using POST /api/v2/telephony/providers/edges/{edgeId}/siptrunks for provisioning)

The failure rate appears to correlate with high-concurrency scenarios, specifically when more than 50 concurrent registration attempts are initiated within a 60-second window. This suggests a potential rate-limiting behavior or a state synchronization issue within the Genesys Cloud SIP signaling layer, although no specific rate-limit headers (e.g., Retry-After) are present in the 407 response.

Has anyone encountered similar issues with SIP trunk authentication under load? We are considering implementing an exponential backoff retry mechanism on our end, but we want to ensure this is not a known limitation or a misconfiguration in how we are handling the Proxy-Authenticate challenge-response cycle. Any insights into the expected behavior of the SIP edge during high-volume provisioning would be greatly appreciated.