Howto:Getting CDPN from SIP/INVITE
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Registered interfaces
The CDPN is extracted from To-URI (no from Request-URI) if option /get-cdpn-from-request-uri is not set.
- RFC-3261 8.2.2.1 To and Request-URI
Typically, a UA that uses the REGISTER method to bind its address-of-record to a specific contact address will see requests whose Request-URI equals that contact address.
All other interface types
The CDPN is extracted from Request-URI (no from To-URI) due to this recommendations:
- RFC-3398 ISUP to SIP Mapping
If the Request-URI and the To header field of a request received at a gateway differ, Section 7.2.1.1 recommends that the To header (if it is a telephone number) should map to the Original Called Number parameter, and the Request-URI to the Called Party Number parameter.
- RFC-4497 Interworking between SIP and QSIG
When mapping a SIP INVITE request to a QSIG SETUP message, the gateway SHALL convert the URI in the SIP Request-URI to a number and include that number in the QSIG Called party number information element. NOTE: The To header should not be used for this purpose. This is because re-targeting of the request in the SIP network can change the Request-URI but leave the To header unchanged. It is important that routing in the QSIG network be based on the final target from the SIP network.