IMS P-CSCF Switchover via S-CSCF Intermediary
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Solution Overview
Problem
In communication networks, terminal devices experience temporary loss of IMS call connectivity due to failures in registered P-CSCF nodes, leading to unacceptable downtime, especially for critical services like emergency call centers.
Innovation Solution
Implementing a switchover service where the S-CSCF node forwards IMS call requests to a secondary P-CSCF node upon failure, ensuring continuous connectivity by proactive registration and substitution, utilizing the shared data layer for subscription verification and IP address location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a terminal device registers a single P-CSCF node with the S-CSCF node, then the system structure remains simple and easy to manage, but the terminal device loses passive IMS call connectivity when the registered P-CSCF node fails
Solution Approach 1:
The terminal device proactively registers multiple P-CSCF nodes (primary and secondary) with the S-CSCF node before any failure occurs. This preliminary registration ensures that when the primary P-CSCF node fails, the terminal device can immediately switch to the secondary P-CSCF node without experiencing connectivity loss, thus improving reliability while maintaining manageable system complexity
Solution Approach 2:
The S-CSCF node acts as an intermediary that manages the registration and switchover between multiple P-CSCF nodes. It stores the associations between terminal devices and multiple P-CSCF nodes, enabling seamless failover while keeping the terminal device unaware of the complexity involved in managing multiple P-CSCF registrations
2Reliability
If the terminal device automatically registers another P-CSCF node after a failure, then connectivity can be restored, but the terminal device suffers from loss of passive IMS call connectivity during the failure time interval
Solution Approach 1:
The terminal device performs preliminary registration with multiple P-CSCF nodes before failure occurs, so that upon detection of primary P-CSCF failure, it can immediately utilize the pre-registered secondary P-CSCF node. This eliminates the time delay associated with automatic re-registration and restores connectivity instantly, thereby reducing downtime while maintaining reliable passive call connectivity
3Reliability
If the S-CSCF node forwards IMS call requests to a single registered P-CSCF node, then the forwarding process is simple and direct, but the system cannot handle P-CSCF node failures
Solution Approach 1:
The terminal device pre-registers multiple P-CSCF nodes (primary and secondary) with the S-CSCF node before any failure occurs. The S-CSCF node stores this information and is configured to forward IMS call requests to the primary P-CSCF node initially, and automatically switch to the secondary P-CSCF node upon detecting a failure. This preliminary setup enables reliable call connection availability while maintaining relatively simple forwarding logic
Solution Approach 2:
The S-CSCF node serves as an intermediary that manages the complexity of multiple P-CSCF node registrations and failover logic. It handles the forwarding of IMS call requests to appropriate P-CSCF nodes based on their operational status, shielding the terminal device from the complexity of multi-node management while ensuring reliable call connectivity
Data Source
Figure 1
AI summary
A method for operating an IMS of a communication network, wherein a first terminal device connected to a communication network registers with a first P-CSCF node of an IMS of the communication network, a second terminal device connected to the communication network sends an IMS call request to an S-CSCF node of the IMS, the IMS call request requesting an IMS call connection to the first terminal device, and the S-CSCF node receives the sent IMS call request and forwards the received IMS call request to the first P-CSCF; an IMS for a communication network, a communication network and a computer program product.