2.3.2. P-Access-Network-Info

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RFC Text

2.3.2. P-Access-Network-Info

The P-Access-Network-Info header field may contain the Network Provided Location Information (NPLI). The NPLI is described in [TS23.228].

A proxy in possession of appropriate information about the access technology might insert a P-Access-Network-Info header field with its own values. Such values are identified by the string "network-provided" defined in [RFC7315]. Based on operator policy, roaming agreement, or both, the local time of the visited network may be included.

The Call Data Records (CDRs) generated within the IP Multimedia Subsystem (IMS) have to contain the NPLI in order to guarantee correct billing. When an IMS session is modified, the NPLI also needs to be stored, as the location of the user at the time when the session is modified may generate a charging event. In case of a session modification event at IMS, the NPLI needs to be provided:

* when the bearer establishment is triggered, or

* at session release when the bearer deactivation is triggered, or

* when the bearer modification is triggered, e.g., a QoS modification for the use of a newly negotiated codec.

In some scenarios, the bearer modification may be triggered by the proxy upon reception of a Session Description Protocol (SDP) answer within the SIP 2xx response to the SIP INVITE request. In such case, the NPLI needs to be provided within the SIP ACK request. However, [RFC7315] does not allow the usage of the P-Access-Network-Info header field in a SIP ACK request.

Upon reception of the SDP answer within a SIP 2xx response on the SIP INVITE request, a proxy may initiate procedures to obtain the NPLI and may include the P-Access-Network-Info header field with the NPLI in the SIP ACK request.

The P-Access-Network-Info header field shall not be included in SIP ACK requests triggered by non-2xx responses.