SIP Access To Parameters in To Header


This feature gives the host read and write access to the parameter field of the "To" header of the initial INVITE request. The SIP stack reports to the host the parameters (if present) in the "To" header of the INVITE within the Request for Service with Data or PPL Event Indication for subsequent data. This reporting is disabled by default.

The SIP stack uses the parameters provided by the host in the Outseize or Route Control messages (and PPL Event Request message for subsequent data) for the "To" header of an outbound initial INVITE message.

Pertinent Specifications

RFC 3398 - ISUP to SIP Mapping

RCF 3261 - Session Initiation Protocol

Internet draft-yu-tel-url-08.txt

Benefits to Customer

The Internet draft-yu-tel-url-08.txt introduced the following three parameters in the tel URI to support number portability (NP) and free phone service:

routing number ("rn=")

npdi-dip-indicator ("npdi")

carrier-id-code ("cic=")

The required or desired parameters might be included in the parameter field of the "To" header in the INVITE request. In particular, customers can have the CSP report the "cic=" parameter to the host. For outbound calls, the host must supply this parameter.

Important! The SIP stack does not support telephone URI fully but it allows telephone numbers to be used as username or hostname.

The following is an example of the INVITE message with the "cic=" parameter highlighted.




INVITE sip:+022536183361088@ SIP/2.0

From: <sip:6187851270@>;tag=fdf55690-d88a384c-13c4-348ce5-46943ed9-348ce5

To: <sip:+022536183361088@>;cic=+1-0008

Call-ID: 591b57d3-29373-22811-cd4572bd-22483-52549@

CSeq: 5101 INVITE

Via: SIP/2.0/UDP;branch=z9hG4bK-348ce5-cd466144-dfe1fb7

User-Agent: Nortel DMS-10UA/v2.1.001

Accept: application/sdp

P-Asserted-Identity: <sip:6187851270@;user=phone>

Privacy: none

Remote-Party-ID: <sip:6187851270@;user=phone>; party=calling; privacy=off

Max-Forwards: 70

Supported: 100rel,replaces


Contact: <sip:6187851270@>

Content-Type: application/SDP

Content-Length: 167



o=- 162175548 463391812 IN IP4

s=SIP Call

c=IN IP4

t=0 0

m=audio 20008 RTP/AVP 0

a=rtpmap:0 PCMU/8000






API and TLVs


PPL Event Indication (0x0043)

PPL Event Request (0x0044)

Route Control (0x00E8)

Outseize Control (0x002C)

Request for Service with Data (0x002D)


SIP To Parameter (0x2945)

SIP Message Information Mask TLV (0x027F)


Call Flows

The following call flow shows a SIP call between two CSPs.


This feature allows the host to instruct the SIP stack to insert parameters in the "To" header of the outbound INVITE request. By default, the SIP stack does not add this parameter.

The CSP acts as the User Agent Server (UAS) reporting to the host the parameter, in the inbound INVITE message, within the Request for Service message or PPL Event Indication message for subsequent data. This parameter is reported using the new TLV - SIP To Parameter (0x2945).

Configuring and Querying with API

This feature is disabled by default. To enable it, set bit 22 of the data part in the SIP Message Information Mask TLV (0x027F) and send it within the VoIP Protocol Configure (0x00EE) message.

Configuring with CSA

Refer to Configuring SIP in the Converged Services Administrator User’s Guide to configure with SwitchKit CSA.