SIP 408 Timeout on BYOC Trunk Failover in AP-Southeast-1

Need some help troubleshooting SIP 408 Request Timeout when routing outbound calls via Genesys Cloud Architect to our secondary BYOC trunk in the Singapore region. The primary carrier is healthy, but failover logic triggers the backup trunk which consistently drops the call after 12 seconds despite correct SIP URI configuration. We have verified the trunk credentials and outbound routing rules, yet the issue persists only for specific DIDs.

You need to check the SIP trunk timeout configuration in Genesys Cloud. The 12-second delay suggests the platform is waiting for a provisional response from the carrier. In AP-Southeast-1, network latency to some providers is higher. Genesys Cloud defaults to a specific SIP timeout value. If the carrier does not send a 100 Trying or 180 Ringing quickly, the system returns a 408. This is not a bug in the failover logic. It is a timing mismatch.

First, verify the SIP trunk settings in the Admin portal. Look for the “SIP Trunk Timeout” field. The default is often too low for international legs. Increase this value to 20 seconds. This gives the carrier more time to respond before Genesys drops the INVITE.

Second, check the outbound route configuration. Ensure the “Max Retry” setting is not set to zero. If the first INVITE fails, the system should retry immediately. Sometimes, the failover trunk has a different codec negotiation delay. Force the codec to G.711 u-law. This avoids transcoding delays during the handshake.

Here is a sample curl command to check the trunk settings:

curl -X GET "https://api.us-east-1.genesyscloud.com/v2/organizations/{organizationId}/trunks/{trunkId}" \
-H "Authorization: Bearer {access_token}" \
-H "Content-Type: application/json"

Look for the sip_trunk_timeout property. If it is missing, the default applies. Contact your carrier support team. Ask them to check their SIP proxy logs. They might be dropping the INVITE silently. This happens with some Asian carriers during peak hours. The 408 is a symptom, not the root cause. The root cause is usually the carrier not responding fast enough. Adjusting the timeout in Genesys usually fixes the immediate drop. But you need to monitor the latency. If it stays high, consider adding a SIP proxy closer to the region. This reduces the round-trip time. It helps with reliability during failover events.

The root cause here is the platform’s default SIP timer expiring before the secondary carrier can respond, especially with the added latency in AP-Southeast-1. The suggestion above about checking trunk settings is valid, but for load testing scenarios, you often need to adjust the keep-alive intervals to prevent premature timeouts. In Genesys Cloud, you can’t directly change the SIP timeout via the UI, but you can influence it by ensuring the BYOC trunk configuration includes proper OPTIONS ping intervals. Try setting the SIP options ping interval to 30 seconds and verify the trunk’s SIP URI includes the correct transport parameter (e.g., ;transport=udp or ;transport=tcp). If the issue persists, check the Genesys Cloud API logs for SIP trace details to see if the 100 Trying response is being dropped. Running a simple JMeter script to simulate SIP OPTIONS requests to the secondary trunk can help isolate whether it’s a network or configuration issue.

Check your BYOC trunk configuration for strict OPTIONS ping intervals. The 408 often stems from carrier-side security dropping idle SIP sessions before the 12-second timer expires.

Verify the secondary carrier accepts these keep-alives.