Troubleshooting SIP 491 Request Terminated Errors in Genesys Cloud CX CTI Integrations by Analyzing Network Packet Captures

How-To-Articles
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Troubleshooting SIP 491 Request Terminated Errors in Genesys Cloud CX CTI Integrations by Analyzing Network Packet Captures

What This Guide Covers

This guide details the process of diagnosing and resolving SIP 491 “Request Terminated” errors occurring in Genesys Cloud CX CTI integrations. The end result is a fully functional CTI integration where calls can be successfully placed and handled without intermittent 491 errors, along with the ability to proactively identify network or configuration issues before they impact end-users.

Prerequisites, Roles & Licensing

  • Genesys Cloud CX CX 2 or higher (required for advanced network diagnostics).
  • Telephony > Trunk > View & Edit permission.
  • Telephony > CTI Adapter > View & Edit permission.
  • Access to network packet capture tools (Wireshark, tcpdump, Genesys Cloud Network Trace).
  • Familiarity with SIP messaging and basic TCP/IP networking concepts.
  • Genesys Cloud Network Trace feature requires a support case to enable.
  • CTI Adapter must be using SIP as the signaling protocol (not WebRTC).

The Implementation Deep-Dive

1. Understanding the SIP 491 Error and Its Implications

The SIP 491 “Request Terminated” error indicates that the call leg was prematurely terminated by the responding party. In a Genesys Cloud CX CTI integration, this usually means the trunk provider or the CTI adapter itself rejected the call attempt. While seemingly straightforward, the root cause can be complex, ranging from network issues to configuration mismatches. Simply restarting the CTI adapter is rarely a permanent solution and often masks a deeper problem.

The Trap: Immediately assuming the issue lies within the CTI adapter itself. While the adapter can be the source of the problem, the more common cause is a misconfigured trunk, a network reachability issue, or a security policy blocking the SIP traffic.

2. Capturing Network Traffic with Genesys Cloud Network Trace

Genesys Cloud offers a built-in Network Trace feature, allowing packet capture between the Genesys Cloud platform and a specified trunk. This is the preferred method for troubleshooting, as it provides visibility into the SIP signaling without requiring access to the underlying network infrastructure.

  1. Open a support case with Genesys Cloud support requesting the Network Trace feature to be enabled for the affected trunk. Specify the SIP Trunk ID.
  2. Once enabled, initiate a call through the CTI adapter while the trace is active.
  3. Genesys Cloud Support will provide a PCAP file containing the captured network traffic. Download and open the file in Wireshark.

The Trap: Activating the Network Trace after the issue has subsided. The trace must be active during the problematic call attempt to capture the relevant SIP messages.

3. Analyzing the PCAP for SIP 491 Errors

Open the PCAP file in Wireshark and apply a SIP filter (sip). Examine the SIP messages before and around the 491 response. Focus on the following:

  • The INVITE message: Verify the From, To, Call-ID, and Contact headers are correctly populated and match the expected values from the CTI adapter. Incorrect header values can cause the trunk provider to reject the call.
  • The 180 Ringing message: If a 180 Ringing message is received, it confirms the call reached the destination. The 491 error then likely indicates an issue after the ringing stage.
  • The 491 Request Terminated message: Examine the Reason header within the 491 response. It might provide a hint about the cause of the termination (e.g., “Call rejected”, “Unsupported media”).
  • Timing gaps: Look for significant delays between SIP messages. Network latency can contribute to call failures.

Code Example (Wireshark Filter): sip.response.code == 491

4. Correlating the Trace with CTI Adapter Logs

Simultaneously, review the CTI adapter logs for corresponding error messages or warnings that correlate with the timing of the 491 error in the network trace. CTI adapter logs often provide context or specific error codes that can help pinpoint the issue. The log level must be set to DEBUG or TRACE for sufficient detail.

The Trap: Ignoring the CTI adapter logs entirely. The logs provide crucial context and can reveal issues like incorrect SIP credentials or unsupported codecs.

5. Common Root Causes and Resolutions

Based on the network trace and CTI adapter logs, consider the following potential root causes:

  • Trunk Configuration Issues: Incorrect SIP credentials, mismatched codecs, or unsupported features configured on the trunk. Verify the trunk settings in Genesys Cloud match the requirements of the trunk provider.
  • Network Reachability: Firewall rules blocking SIP traffic (UDP/TCP port 5060/5061), routing issues preventing communication between Genesys Cloud and the CTI adapter. Use traceroute to verify network connectivity.
  • Codec Negotiation Failure: The CTI adapter and trunk provider are unable to agree on a common codec. Configure a compatible codec list on both sides.
  • Security Policies: Security policies (e.g., TLS inspection) interfering with the SIP signaling. Ensure the correct certificates are installed and trusted.
  • MTU Issues: Maximum Transmission Unit (MTU) mismatches can cause packet fragmentation and lead to call failures. Adjust the MTU size on the network devices.

6. Advanced Troubleshooting: Analyzing RTP Traffic

If the SIP signaling appears correct, the issue may be related to RTP (Real-time Transport Protocol) traffic. While a 491 error usually indicates a signaling issue, intermittent RTP failures can sometimes manifest as a 491.

  1. In Wireshark, apply an RTP filter (rtp).
  2. Look for packet loss, jitter, and out-of-order packets.
  3. Analyze the RTP payload type to verify the correct codec is being used.

Validation, Edge Cases & Troubleshooting

Edge Case 1: Intermittent 491 Errors

The failure condition: 491 errors occur sporadically, making it difficult to capture the issue in a network trace.
The root cause: Often caused by transient network congestion or intermittent firewall issues.
The solution: Monitor network performance metrics (latency, packet loss) during peak hours. Consider increasing bandwidth or optimizing firewall rules. Use long-term monitoring tools to identify patterns.

Edge Case 2: 491 Errors with “Call Barring” Reason

The failure condition: The 491 response includes a Reason header indicating “Call Barring”.
The root cause: The trunk provider has blocked the call based on configured call barring rules (e.g., blocking calls to specific destinations or from specific numbers).
The solution: Review the trunk provider’s call barring configuration and adjust accordingly.

Edge Case 3: 491 Errors After a Genesys Cloud Platform Upgrade

The failure condition: 491 errors begin to occur immediately after a Genesys Cloud platform upgrade.
The root cause: The upgrade may have introduced a compatibility issue with the CTI adapter or trunk configuration.
The solution: Contact Genesys Cloud support to report the issue. They may have identified a known issue or require additional configuration changes.

Official References