Charging Function Cache Staleness Handling
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Solution Overview
Problem
Stale cache data in the charging system of cellular communication networks can cause failures in charging operations by directing requests to the wrong subscriber database server, leading to revenue loss or poor customer experience until the cache is cleared.
Innovation Solution
The charging function performs a re-lookup from a DNS server to obtain the latest subscriber database server ID when a 'subscriber not found' error occurs, updates the cache, and forwards the request to the new server, ensuring accurate charging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the CHF maintains a mapping of subscribers to respective SDSs in cache to handle high number of transactions, then transaction handling speed is improved, but stale cache data causes charging operation failures
Solution Approach 1:
The CHF implements a feedback mechanism where the response from SDS is monitored. When a 'subscriber not found' error is detected, the system automatically triggers a cache invalidation and re-lookup process. This feedback loop ensures that stale cache data is detected and corrected, maintaining charging operation reliability while preserving the performance benefits of caching.
Solution Approach 2:
The cache system transitions from a static structure to a dynamic one with automatic invalidation capabilities. The cache entry for subscriber mapping is made dynamic by allowing it to be invalidated and updated based on runtime conditions (error responses from SDS). This enables the system to adapt to changes in subscriber-SDS mappings without sacrificing the speed advantages of caching.
2Productivity
If the CHF uses cache to store subscriber-SDS mapping, then system performance is improved, but system complexity increases due to cache management
Solution Approach 1:
The cache management system performs self-service through automatic invalidation triggered by error conditions. Instead of requiring external intervention or complex manual cache management, the system automatically detects when cache data becomes stale (through error responses) and invalidates the relevant cache entries. This reduces the operational complexity of cache management while maintaining high system performance.
3Duration of action of stationary object
If stale cache data is not cleared, then system operations continue uninterrupted, but charging failures occur due to wrong SDS routing
Solution Approach 1:
The system takes preliminary action by proactively invalidating cache entries when errors are detected, rather than waiting for cache expiration or manual intervention. This preliminary invalidation action prevents future charging failures by ensuring that the cache contains up-to-date mappings before they are needed, maintaining both system continuity and reliability.
Data Source
AI summary
A charging function (CHF) of a carrier network may perform charging operations despite stale cache data. For example, the CHF may request that a first subscriber database server (SDS) perform operations associated with a charging request associated with a subscriber based on a mapping of the subscriber to the first SDS in the cache of the CHF. The CHF may receive a response indicating the first SDS failed to perform the operations associated with the charging request and request a mapping of the subscriber to a SDS of a plurality of SDSs from a server mapping subscribers of the carrier network to respective SDSs of the plurality of SDSs. The CHF may receive a mapping of the subscriber to a second SDS of the plurality of SDSs and request that the second SDS perform the operations associated with the charging request.