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Understanding Session Border Controllers: Comprehensive Guide to Designing, Deploying, Troubleshooting, and Maintaining Cisco Unified Border Element (CUBE) Solutions by Gonzalo Salgueiro, Kaustubh Inamdar, Steve Holl, Chidambaram Arunachalam, Arunachalam Chidambaram, Kyzer Davis, Felipe Garrido

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Appendix A

Q.850 Release Cause Values

Table A-1 outlines the call disconnect cause values, as defined by the International Telecom Union’s standard, defined by Q.850. These numeric cause values map the reason for disconnect into a specific description for the nature of the call disconnect. These codes outline both normal disconnect scenarios, and failure or error conditions, and are common across vendors. Understanding what some of these common codes represent support the troubleshooting of issues. These codes are referenced in several chapters in this publication.

Table A-1 Q.850 Release Cause Values

Standard Category

Typical Scenarios

Q.850 Cause Code

Q.850 Release Cause Description

Unallocated (unassigned) number

  • The number is not in ...

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