Cellular Session Control with NAT Translation Reporting
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Solution Overview
Problem
Network address translation (NAT) in the user plane of a cellular network leads to user IP address mismatches, causing failures in user-specific requests and inaccurate charging data records, which are not addressed by existing technologies.
Innovation Solution
A mechanism is introduced where the session control entity requests and receives information about network address translation from the user plane entity, enabling the session control entity to be aware of the translation and adjust policies accordingly, ensuring correct binding information is maintained and reported.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If network address translation is performed in the user plane to conserve IP addresses and enable multiple users to share a common IP address, then IP address conservation and user connectivity are improved, but user IP address identification and binding information accuracy deteriorate
Solution Approach 1:
The patent introduces a session management function as an intermediary between the user plane and the control plane. This session management function maintains binding information that maps translated IP addresses to original user IP addresses, enabling accurate identification and charging while allowing NAT to function for address conservation.
Solution Approach 2:
The patent implements feedback mechanisms where the user plane entity reports address translation events to the session management function. This feedback loop ensures that the control plane is informed about NAT operations, allowing it to maintain accurate binding information for charging and policy enforcement.
2Reliability
If network address translation is performed in the user plane, then user connectivity through NAT is improved, but charging data record accuracy and policy enforcement deteriorate
Solution Approach 1:
The patent performs preliminary actions by establishing binding information in the session management function before address translation occurs. This pre-established mapping allows accurate charging data records to be generated even though the actual translation happens later in the user plane, ensuring measurement precision is maintained.
3Loss of information
If the session control entity is made aware of address translation through policy requests and translation detection rules, then binding information accuracy is improved, but signaling overhead and processing complexity increase
Solution Approach 1:
The patent makes the session management function multi-functional by combining its existing session management responsibilities with the additional task of maintaining binding information for NAT scenarios. This universal approach allows the same entity to handle both session control and address translation tracking, reducing overall system complexity despite the added functionality.
Data Source
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AI summary
The invention relates to a method for operating a session control entity (100) configured to control a data packet session of a user (10) in a cellular network (30), the method comprising: - transmitting a policy request to a policy control entity (300) of the cellular network, requesting at least one policy rule for the data packet session, - receiving a policy response from the policy control entity (300) including the at least one policy rule for the data packet session, the policy response further comprising a request to provide information about an address translation carried out in a user plane on the data packets of the data packet session, - transmitting rules for handling the data packet session to a user plane entity (500) configured to handle the user plane of the data packet session, the rules comprising a translation detection rule by which the user plane entity (500) is requested to inform the session control entity (100) about the address translation that has taken place in the user plane.