IMS P-CSCF Header Insertion for Trust Domain Extension
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Solution Overview
Problem
In IP Multimedia Subsystem (IMS) networks, extending the trust domain to a corporate network connected over a Gm reference point leads to issues with P-Asserted-Identity headers, where the identity may not represent the current IMS user, causing failures or incorrect processing of SIP messages.
Innovation Solution
A P-CSCF in the IMS network inserts a new P-Served-User header in SIP messages when the P-Asserted-Identity does not match a trusted entity's identity, allowing the S-CSCF to determine the served user using this header instead, ensuring proper authentication and service execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the trust domain is extended to a corporate network connected over a Gm reference point, then communication between IMS network and corporate network is enabled, but the P-Asserted-Identity header may not represent the current IMS user causing message processing failures
Solution Approach 1:
The patent segments the identity information into two separate headers: P-Asserted-Identity (carried by corporate network) and P-Served-User (inserted by P-CSCF). This segmentation allows each header to serve its specific purpose without conflict, resolving the reliability issue while maintaining trust domain extension
Solution Approach 2:
The P-CSCF acts as an intermediary that receives SIP messages from the corporate network, inserts the P-Served-User header with the correct IMS user identity, and forwards the message to the S-CSCF. This intermediary function ensures that the S-CSCF receives accurate identity information even when the P-Asserted-Identity does not represent the current user
2Ease of operation
If P-Asserted-Identity header is used to identify the served user, then authentication can be performed, but the header may contain unknown or incorrect identity when received from corporate network
Solution Approach 1:
The P-CSCF performs preliminary action by inserting the P-Served-User header before forwarding the message to the S-CSCF. This ensures that the S-CSCF receives the correct user identity information in advance, allowing proper authentication without relying on potentially incorrect P-Asserted-Identity
3Productivity
If direct user-to-user SIP sessions are allowed, then communication efficiency is improved, but the S-CSCF cannot control or charge user access to services
Solution Approach 1:
The S-CSCF serves as a mandatory intermediary in the SIP message route between users. Even though direct user-to-user communication is enabled, all messages must pass through the S-CSCF which uses the P-Served-User header to identify the served user, perform service control, and enable charging while maintaining communication efficiency
Data Source
AI summary
A method and apparatus for handling a Session Initiation Protocol communication in an IP Multimedia Subsystem (IMS) network. A Proxy Call Session Control Function receives a Session Initiation Protocol message sent from a trusted remote network. The P-CSCF adds to the message a further header, which identifies a Public User Identity of a trusted entity located in the remote network served by a Serving Call Session Control Function in the IMS network. The message is then sent to the S-CSCF. The S-CSCF, and any other node that the message is sent to, knows from the presence of the further header to use the Public User Identity of the trusted entity to determine the served user rather than the P-Asserted Identity contained in the SIP message.