PCRF NAT Binding Awareness for Session Management

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Solution Overview

Problem

The presence of Network Address Translation (NAT) or Network and Port Address Translation (NAPT) between User Equipment (UE) and the Application Function (AF) causes issues with session binding between Rx and Gx sessions in the Policy and Charging Control Function (PCRF), leading to ineffective session management.

Innovation Solution

Making the PCRF aware of the NAT bindings of the UE by sending messages for IP address and port allocations/deallocations, pre-allocating port ranges, and using a common algorithm to determine port numbers, ensuring the PCRF can perform accurate session binding even with NAT/NAPT present.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If NAT/NAPT is deployed between UE and AF to conserve IPv4 addresses, then IPv4 address depletion is mitigated, but session binding between Rx and Gx sessions in PCRF fails

Engineering Contradiction:

ImproveIPv4 address conservationVSAvoidsession binding reliability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The gateway acts as an intermediary between the NAT function and PCRF, extracting and forwarding NAT binding information (translated IP addresses and port mappings) to the PCRF. This intermediary mechanism allows the PCRF to maintain accurate session binding despite the address translation occurring in the network path between UE and AF.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system implements feedback by having the gateway continuously monitor and report NAT binding changes to the PCRF. When NAT translations are created, modified, or deleted, this information is fed back to the PCRF, enabling dynamic session binding updates that reflect the current network state despite address translation.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If NAT bindings are made transparent to PCRF by gateway intervention, then session binding accuracy is improved, but signaling complexity between gateway and PCRF increases

Engineering Contradiction:

Improvesession binding accuracyVSAvoidsignaling complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The gateway leverages its existing multi-functional role in the network (IP-CAN session management, charging enforcement) to also handle NAT binding information extraction and forwarding. By utilizing the gateway's existing communication infrastructure with PCRF, the solution avoids creating entirely new signaling pathways, thereby reducing additional complexity while maintaining session binding accuracy.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9537821B2Method for PCC support for scenarios with NAT in the GW

Publication Date: 2017.01.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The invention relates to a method and system for network communication wherein a Policy and Charging Control Function (PCRF; 6) is aware of any Network Address Translator (NAT; 7) bindings of the user equipment (UE; 2).