RFC 3455

Q: What does the Introduction section cover in RFC 3455 — SIP P-Headers (3GPP)?

The Introduction section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 3455 — SIP P-Headers (3GPP). This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Defined P-Headers section cover in RFC 3455 — SIP P-Headers (3GPP)?

The Defined P-Headers section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 3455 — SIP P-Headers (3GPP). This content is part of the BLACKLABS RFC Reference Library.

Q: What does the P-Charging-Vector Detail section cover in RFC 3455 — SIP P-Headers (3GPP)?

The P-Charging-Vector Detail section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 3455 — SIP P-Headers (3GPP). This content is part of the BLACKLABS RFC Reference Library.

Q: What does the Security Considerations section cover in RFC 3455 — SIP P-Headers (3GPP)?

The Security Considerations section provides detailed technical specifications, security considerations, and implementation guidance as documented in RFC 3455 — SIP P-Headers (3GPP). This content is part of the BLACKLABS RFC Reference Library.

BLACKLABS

Private Header (P-Header) Extensions to SIP for 3GPP

Informational

January 2003

Abstract: Defines private SIP header field extensions (P-Headers) for use within 3GPP IMS networks. These headers carry 3GPP-specific information such as access network information, charging identifiers, and visited network identity.

Canonical source: https://www.rfc-editor.org/rfc/rfc3455 | IETF Datatracker

1. Introduction

▶

Standard SIP does not carry the 3GPP-specific information needed for IMS operation — access type, charging correlation, network identity, and associated URIs. The P-Header extensions (prefixed with 'P-') provide this information within the trusted 3GPP IMS domain.

P-Headers are intended for use only within a 'Trust Domain' of 3GPP network elements. They MUST NOT be sent to or from untrusted entities. The P-CSCF is responsible for adding or stripping P-Headers at the trust boundary.

2. Defined P-Headers

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Header	Description	Added By	Used By
P-Access-Network-Info	Access type and cell-id (e.g., 3GPP-E-UTRAN-FDD; utran-cell-id-3gpp=...)	UE → P-CSCF	S-CSCF, AS (location/charging)
P-Associated-URI	List of associated public user identities	S-CSCF → UE	UE (identity selection)
P-Called-Party-ID	Effective Request-URI (after alias resolution)	S-CSCF	AS (service invocation)
P-Charging-Function-Addresses	CCF/ECF addresses for offline/online charging	P-CSCF/S-CSCF	Charging functions
P-Charging-Vector	IMS Charging Identifier (ICID), access correlation info	P-CSCF	All IMS nodes (charging correlation)
P-Visited-Network-ID	Visited PLMN identity (for roaming)	P-CSCF	I-CSCF, S-CSCF

3. P-Charging-Vector Detail

▶

P-Charging-Vector is the most complex P-Header, carrying multiple parameters for end-to-end charging correlation:

icid-value: IMS Charging Identifier — globally unique ID for the SIP dialog
icid-generated-at: Address of the node that created the ICID
orig-ioi: Originating Inter-Operator Identifier (for roaming billing)
term-ioi: Terminating Inter-Operator Identifier
access-network-charging-info: Bearer-level charging info (GGSN/PGW GCID)

4. Security Considerations

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P-Headers contain sensitive subscriber and network info — MUST be stripped at trust boundary
P-Access-Network-Info reveals UE location (cell-id) — privacy-critical
P-Charging-Vector manipulation could cause billing fraud — integrity must be protected
P-CSCF is the trust boundary: adds P-Headers from UE info and strips incoming P-Headers from untrusted sources

Trust Domain: P-Headers are only valid within the SIP trust domain (operator's IMS core). The P-CSCF acts as the gatekeeper — inserting verified P-Headers from the access network and removing any P-Headers received from untrusted sources.