Support of extension header "P-Called-Party-ID" and/or "X-ORIGINAL-DDI-URI" in SIP INVITE messages (kb3906)

The information in this article applies to:

  • SwyxWare v6.12
  • SwyxWare 6.20 Quickfix 09-02-20

[ Summary | Information ]


This article describes the support of the extension header  "X-ORIGINAL-DDI-URI" in SIP INVITE messages and "P-Called-Party-ID" (RFC3455), especially in case of forwarding.


An external call from PSTN (A) to a mobile device (B) is forwarded to a SwyxWare user (C).

Usually in SIP you will find the caller number in the From header and the called number (here the number assigned to the SIP account) in the To header.

In this case a third party, the mobile subscriber (B), is involved. For the forwarded call the new destination number (here SwyxWare user (C)) should be entered in the To header.
SwyxWare accepts that the first destination number (here the number of the mobile device (B)) remains in the To header if the new destination number is entered in an additional field, the proprietary X-Header "X-ORIGINAL-DDI-URI" or the standard header "P-Called-Party-ID" (RFC3455) is used.

Further you can create a new registry key "SIPUseToHeaderAsRedirectingNumber" (DWORD) under


This key will define which number is signalled as caller number:


  • Value 1 - the number of the To heder (here forwarding mobile device (B))
  • Value 0 or no registry key - the number of the first caller (A) will be signalled

The registry key will only be taken in account if there is a special forwarding which


  • contains the X-Header "X-ORIGINAL-DDI-URI"


  • the SIP URI user part of the X-Header differs from the SIP URI user part of the To header.



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