A call's SIP Header carries fields that CCaaS can read to identify where it should go — through a Parameter condition using the SIP Header type, or a rule in Call Routing. The exact fields present and their format vary by carrier and phone system, so only fields actually passed through in live traffic can be used.

User-Agent

User-Agent: Phones-R-Us v12.32.4

The USER-AGENT header field describes the device or system that originated the SIP request.

From

From: "Sally" <sip:[email protected]>

The FROM header field indicates the contact information of the call's initiator — "Sally" in this example.

To

To: "John" <sip:[email protected]>

The TO header field contains information about the called party — "John" in this example. This is often where a dialed number, extension, or a prefix added by a UC platform appears — see Call Routing Methods for a worked example of matching against this field.

P-Asserted-Identity

P-Asserted-Identity: "Sally Thompson" <sip:[email protected]>

The P-ASSERTED-IDENTITY header field carries the verified identity of the user sending a SIP message, used among trusted SIP entities. It is commonly used in call centers to present a customer's calling number rather than the raw telephone number — "Sally Thompson" in this example.

Additional Header Options

CONTACT, FROM (Caller ID Only), and REFERRED-BY are also selectable as a SIP Header type in a Parameter condition, alongside a free-form option for any custom header a phone system supplies. See Parameters for the full list.