5G Edge Session Steering to Application Servers via PCF Filters
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Solution Overview
Problem
In 5G networks with edge computing, the user plane function (UPF) is unable to steer packets to edge application servers (EASs) due to unknown routes advertised by border gateway protocol (BGP) and interior gateway protocol (IGP), necessitating methods for session steering to application servers.
Innovation Solution
Implementing traffic influence routing rules and filters in the control plane (CP) to direct packets to edge application servers by storing and generating filters based on service addresses and gateway addresses, using network slice selection assistance information, and updating existing filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If BGP/IGP routing is used for application servers, then scalability and resilience are improved, but the UPF cannot steer packets to edge application servers because routes are unknown
Solution Approach 1:
The PCF acts as an intermediary between the AF and UPF. The AF provides routing information to the PCF, which then generates traffic filters and transmits them to the UPF. This mediator approach allows the UPF to steer packets to edge application servers without requiring direct route knowledge in the UPF itself, resolving the contradiction between scalability and route information availability.
Solution Approach 2:
The routing control function is segmented into separate components: the AF (application function), the PCF (control plane function), and the UPF (user plane function). Each component handles specific aspects of routing control, allowing the UPF to receive pre-computed traffic filters from the PCF without needing to process complex routing decisions itself, thus maintaining scalability while enabling packet steering.
2Reliability
If traffic influence routing rules are implemented in the control plane, then packet steering to edge application servers is enabled, but device complexity increases
Solution Approach 1:
The complex routing decision logic is extracted from the UPF and placed in the PCF. The PCF receives application service information from the AF, generates appropriate traffic filters, and transmits them to the UPF. This extraction simplifies the UPF while increasing control plane functionality, achieving reliable packet steering without over-complicating the user plane.
Solution Approach 2:
The PCF performs preliminary actions by pre-computing traffic filters based on routing rules received from the AF. These filters are generated in advance and transmitted to the UPF, which can then directly apply them for packet steering without needing to perform complex routing decisions in real-time. This preliminary action reduces operational complexity at the UPF while maintaining steering capability.
Data Source
AI summary
A method includes receiving, by a control plane (CP) from an application function (AF), a traffic influence routing rule comprising a service address representing a destination address of a route to an application server, the traffic influence routing rule specifying a breakout rule for packets of a communicating device addressed to the application server; storing, by the CP, the traffic influence routing rule in a policy control function (PCF); and generating, by the CP, a traffic filter for packets of at least one traffic flow associated with the communicating device, the traffic filter directing packets of the at least one traffic flow that are addressed to the application server to the service address, the traffic filter being generated in accordance with the traffic influence routing rule.