2. Misalignments and 3GPP Use Cases

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RFC Text

2. Misalignments and 3GPP Use Cases

2.1. General

[RFC7315] contains contradictory statements regarding the usage of SIP "P-" header fields in SIP requests and responses, which leave the presence of the SIP "P-" header fields in the SIP requests and responses open to interpretation and different implementations. Statements in Section 5.7 of [RFC7315] are not aligned with the definitions and usage of the SIP "P-" header fields specified in Section 4 of [RFC7315]. This section describes the misalignments that occurred when [RFC3455] was updated and subsequently obsoleted by the publication of [RFC7315], and how they are fixed.

NOTE: In the case of the P-Called-Party-ID header field, allowing it in PUBLISH requests was done deliberately in [RFC7315]. Therefore, it is not considered a misalignment.

Since [RFC7315] was published, 3GPP defined new use cases that require the RFC to be updated. This section describes the 3GPP use cases behind the updates, and the updates needed to [RFC7315] in order to support the use cases.

Section 3 updates [RFC7315], based on the misalignments and 3GPP use cases.

2.2. Misalignments

The following updates are needed in order to fix the misalignments that occurred when [RFC3455] was obsoleted by [RFC7315]:

* P-Associated-URI: Remove the statement that the header field can appear in the SIP REGISTER method.

* P-Called-Party-ID: Delete the statement that the P-Called-Party-ID header field can appear in SIP responses. Add a statement that the P-Called-Party-ID header field can appear in the SIP REFER method.

* P-Access-Network-Info: Add a statement that the P-Access-Network-Info header field can appear in SIP responses.

* P-Charging-Vector: Add a statement that the P-Charging-Vector header field can appear in SIP responses. Add a statement that the P-Charging-Vector header field cannot appear in the SIP ACK method.

* P-Charging-Function-Addresses: Add a statement that the P-Charging-Function-Addresses header field can appear in SIP responses.

The following update is needed in order to clarify the usage of the header compared to [RFC7315]:

* P-Visited-Network-ID: Add a statement that the P-Visited-Network-ID header field cannot appear in the SIP NOTIFY, PRACK, INFO, and UPDATE methods. Add statement that the P-Visited-Network-ID header field can appear in all non-100 (Trying) responses.

2.3. 3GPP Use Cases

2.3.1. General

The following updates are needed in order to implement the 3GPP use cases:

* P-Access-Network-Info: Add statement that the P-Access-Network-Info header field can appear in the SIP ACK method when triggered by a SIP 2xx response.

* P-Charging-Vector: Add statement that the P-Charging-Vector header field can appear in the SIP ACK method when triggered by a SIP 2xx response.

This following sections describe, for individual "P-" header fields, the 3GPP use cases that are the basis for the updates. The use cases are based on the procedures defined in [TS24.229].