PDN Gateway Session Restoration for Collision-Free Failover
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Solution Overview
Problem
In wireless communication systems, there is a challenge in handling collisions during session restoration procedures between mobility management entities (MME) and policy control functions (PCF) when multiple packet data network (PGW) instances are deployed for redundancy, leading to inconsistent session establishment across different PGW instances.
Innovation Solution
A packet data network gateway (PDN) is configured to receive a request to restore an existing session, detect a read lock failure, and send a rejection message with a cause code indicating the correct PGW instance for session restoration, ensuring consistent session establishment across the same PGW instance for MME and PCF communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple PDN gateway instances are deployed for redundancy, then system reliability is improved, but session collision occurs during restoration procedures
Solution Approach 1:
The system performs preliminary actions by establishing a mapping relationship between the MME/ePDG and PDN gateway instances before session restoration is needed. The database stores this mapping information, allowing the system to quickly identify the correct PDN gateway instance during restoration without causing collisions. This preliminary preparation enables reliable session restoration while avoiding conflicts between multiple gateway instances.
2Productivity
If session restoration is performed independently by MME and PCF, then restoration speed is improved, but inconsistent session establishment occurs
Solution Approach 1:
The system implements feedback mechanisms where the MME/ePDG receives feedback information from the PCF about the session restoration status. The PCF provides feedback regarding which PDN gateway instance it has selected for restoration, allowing the MME/ePDG to adjust its restoration process accordingly. This feedback loop ensures that both MME and PCF coordinate their restoration actions, maintaining session consistency while preserving restoration speed.
Solution Approach 2:
The database serves as an intermediary component that stores and manages the mapping relationships between MME/ePDG, PCF, and PDN gateway instances. This intermediary structure allows MME and PCF to independently perform restoration operations while ensuring their actions are coordinated through the shared database. The database mediates the restoration process, preventing conflicts and ensuring consistent session establishment across both entities.
3Reliability
If read lock is acquired for session restoration, then data integrity is improved, but restoration time increases
Solution Approach 1:
The system performs preliminary actions by pre-establishing and storing mapping relationships in the database before session restoration is needed. This preliminary setup allows the system to retrieve the correct PDN gateway instance information without acquiring lengthy read locks during restoration. The database is pre-configured with the necessary mapping data, enabling quick access during critical restoration operations while maintaining data integrity.
Data Source
AI summary
Described are examples for modifying a packet data network (PDN) gateway used for a session in wireless communications where the PDN gateway can receive, for a mobility management entity (MME) or evolved packet data gateway (ePDG), a request to restore an existing session with the first PDN gateway, receive, from a database, and based on attempting to restore the existing session for the MME or ePDG, a read lock failure based on a restoration of the existing session established for the MME or ePDG and a second PDN gateway, and send, for the MME or ePDG, a rejection message in response to the request, where the rejection message includes a cause code indicating to restore the existing session with the second PDN gateway. Other examples relate to the MME or ePDG receiving the rejection message and sending the request to restore the existing session with the second PDN gateway.