HSS Redundancy via SLF Priority Routing
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Solution Overview
Problem
In Next Generation Networks (NGN) with IP Multimedia Subsystem (IMS) architecture, when multiple Home Subscriber Servers (HSS) are present, there is no effective mechanism to ensure continuous access to user information and S-CSCF server selection in case of failure, leading to service disruptions and reduced IMS service quality.
Innovation Solution
Implementing a redundant configuration of HSS servers with synchronized information and a Subscriber Locator Server (SLF) that provides access information to I-CSCF and S-CSCF servers in a predetermined order, allowing seamless switching to alternative HSS servers if one fails, ensuring continuous service by maintaining identical information across HSS servers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple HSS servers are deployed in redundant configuration, then system reliability is improved, but device complexity increases
Solution Approach 1:
The patent divides the HSS server function into multiple independent server instances (HSS-A, HSS-B, HSS-C) that can operate autonomously. Each server stores complete user information, allowing the system to segment the database functionality across multiple nodes while maintaining redundancy and fault tolerance.
Solution Approach 2:
The patent introduces an SLF (Subscriber Locator Function) server as an intermediary component that manages the mapping between subscribers and HSS servers. The SLF server maintains a database that records which HSS server stores information for which subscriber, enabling I-CSCF servers to locate the correct HSS server without direct complex interconnections between all HSS servers.
2Reliability
If HSS servers store identical information, then service continuity is improved, but information synchronization complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring all HSS servers with identical user information databases before any failure occurs. This ensures that when a failure happens, alternative HSS servers already contain the necessary information and can immediately take over without requiring real-time synchronization during the failure event.
Solution Approach 2:
The patent employs copying by creating identical copies of the HSS server database across multiple server instances. Each HSS server maintains a complete copy of user information, enabling failover to any HSS server without information loss. The SLF server manages metadata about which copies are active and their correspondence relationships.
3Speed
If I-CSCF servers store correspondence between HSS servers and users, then access speed is improved, but information management complexity increases
Solution Approach 1:
The patent extracts the correspondence management function from the I-CSCF servers and places it in a dedicated SLF (Subscriber Locator Function) server. The SLF server maintains a separate database that maps subscribers to HSS servers, allowing I-CSCF servers to query this centralized mapping information without managing complex correspondence logic themselves.
Solution Approach 2:
The patent implements universality by making the SLF server a universal component that serves multiple I-CSCF servers and manages correspondence for all users across the entire network. This single SLF server instance (or set of instances) handles the mapping function for the entire system, reducing the burden on individual I-CSCF servers.
Data Source
AI summary
The present invention is to provide a home subscriber server configuration method and system that is accessible in switching to any one of plural HSS servers in a redundant configuration. Information stored in such plural HSS servers (e.g., HSS-A server 40A and HSS-B server 40B) are synchronized as identical information. When an interrogation for a particular HSS server to be accessed from the I-CSCF server 30 or the S-CSCF server 21 is received, the access information for the plural HSS servers 40A, 40B corresponding to the interrogation is returned after rearranging to the predetermined order of priority to the I-CSCF server 30 or the S-CSCF server 21 from which the inquiry is originated. If no response is received from either one of the HSS servers returned from the SLF server 50 within a predetermined time after the access or if no response is received to the resend operations, the I-CSCF server 30 or the S-CSCF server 21 selects the next HSS server from the plural HSS servers and gains access to such HSS server after switching thereto.