Understanding the SIP UID and Caller ID Behaviors 

Introduction

This document serves as a technical reference for understanding SIP (Session Initiation Protocol) User Identification (UID) and Caller ID presentation within a telecommunications environment. It defines the hierarchical logic used when multiple Caller ID sources are available—such as from the trunk, outbound rules, or user extensions. By outlining the priority order and illustrating common call scenarios, this document ensures consistency, transparency, and accuracy in Caller ID presentation across all outbound communications.

Caller ID Sources and Priority

The system decides which Caller ID to display based on the following order of priority:

Outbound Rule

• Highest priority.
• If a Caller ID is set in the outbound rule, it overrides all other settings.
• Used for company-wide or campaign-specific numbers.

Extension

• Second priority.
• Caller ID set at the user or extension level.
• Used to show direct or personal numbers for users or departments.

Advanced SIP Settings

• Third, in line.
• Caller ID sent from the SIP device (e.g., softphone or IP phone).
• May be ignored if overridden by outbound rule or extension.

Call Scenario Analysis

Scenario 1 Complete Override

• Trunk Caller: +18235550199
• Outbound Rule: +15460205678
• Extension: +15150101234
• Result: +15460205678 (Outbound rule takes precedence)

Scenario 2 Extension Override

• Trunk Caller: +18235550199
• Outbound Rule: (Empty)
• Extension: +15150101234
• Result: +15150101234 (Extension used when outbound rule is empty)

Scenario 3 Trunk Passthrough

• Trunk Caller: +18235550199
• Outbound Rule: (Empty)
• Extension: (Empty)
• Result: +18235550199 (Original trunk caller ID preserved)

Scenario 4 Outbound Rule Only

• Trunk Caller: (Empty)
• Outbound Rule: +15460205678
• Extension: (Empty)
• Result: +15460205678 (Outbound rule applied)

Scenario 5 Extension Only

• Trunk Caller: (Empty)
• Outbound Rule: (Empty)
• Extension: +15150101234
• Result: +15150101234 (Extension caller ID used)

Scenario 6 Mixed Configuration

• Trunk Caller: +18235550199
• Outbound Rule: +15460205678
• Extension: (Empty)
• Result: +15460205678 (Outbound rule overrides trunk)

Scenario 7 Outbound Rule with Extension

• Trunk Caller: (Empty)
• Outbound Rule: +15460205678
• Extension: +15150101234
• Result: +15460205678 (Outbound rule has higher priority)

Scenario 8 No Caller ID Available

• Trunk Caller: (Empty)
• Outbound Rule: (Empty)
• Extension: (Empty)
• Result: NO From USER (System default when no caller ID available)

Scenario Analysis