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Collaboration, Voice & AV · Advanced

SIP Dialog

A peer-to-peer SIP relationship between two user agents identified by Call-ID, From tag and To tag that persists for a call.

Definition

A dialog is created by a successful INVITE (or SUBSCRIBE) and includes the state needed for later in-dialog requests such as re-INVITE, BYE or REFER. Within a dialog, separate transactions are tracked by CSeq numbers. Understanding dialogs helps when reading traces with multiple calls on the same trunk.

Example

Filtering a CUBE debug by Call-ID isolates every message for one dialog.

Exam tip

Call-ID plus tags identify the dialog; CSeq identifies the transaction within it.

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