Edge Application Server Discovery Across NAT Using ECS and STUN
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Solution Overview
Problem
The challenge of network address translation (NAT) between the 5G Core (5GC) and edge application servers (EAS) hinders efficient discovery of edge application servers, particularly in scenarios where private IP addressing is used due to address scarcity, affecting the selection of the best EAS for user equipment.
Innovation Solution
The implementation of an enhanced edge application server discovery function (EASDF) that includes mechanisms to handle NAT by adding DNS EDNS client subnet (ECS) options to DNS queries, utilizing both private and public IP addresses, and integrating STUN procedures to determine NATted IP addresses, ensuring accurate EAS selection even with network translation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If private IP addressing is used to address IPv4 scarcity, then address availability is improved, but NAT complexity increases and EAS discovery reliability deteriorates
Solution Approach 1:
The patent introduces the EASDF (Edge Application Server Discovery Function) as an intermediary network function that mediates between the 5GC and EAS. The EASDF receives DNS queries from the 5GC, adds ECS options with accurate IP information, and forwards queries to external DNS servers. This intermediary handles the NAT complexity by maintaining a mapping between private and public IP addresses, ensuring reliable EAS discovery despite private IP addressing.
Solution Approach 2:
The patent modifies DNS query parameters by adding ECS (EDNS Client Subnet) options that include both private and public IP address information. This parameter change enables external DNS servers to understand the NAT relationship and return accurate EAS IP addresses. The ECS option contains subnet information that allows the DNS server to perform accurate routing decisions while respecting the private IP addressing scheme.
2Adaptability or versatility
If NAT is applied between 5GC and EAS, then private IP domain deployment is enabled, but DNS query accuracy deteriorates
Solution Approach 1:
The EASDF acts as an intermediary that receives DNS queries from the 5GC, enriches them with accurate IP information through ECS options, and forwards them to external DNS servers. This mediator ensures that DNS queries maintain accuracy even when NAT is applied, by providing the necessary contextual information about the client's IP address and subnet.
Solution Approach 2:
The patent performs preliminary action by pre-configuring the EASDF with the client's IP address and subnet information before the DNS query is forwarded. The EASDF prepares the ECS option with accurate mapping information in advance, ensuring that when the query reaches external DNS servers, all necessary information for accurate resolution is already in place.
3Measurement precision
If EASDF is introduced for enhanced discovery, then EAS selection accuracy is improved, but network complexity increases
Solution Approach 1:
The EASDF is designed as a multi-functional network function that handles multiple tasks: receiving DNS queries from the 5GC, adding ECS options with IP information, forwarding queries to external DNS servers, and receiving responses. By consolidating these functions into a single EASDF instance, the patent improves EAS selection accuracy without proportionally increasing network complexity.
Data Source
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AI summary
There are provided measures for an enhanced edge application server discovery procedure. Such measures exemplarily comprise receiving, from a network repository function entity, a user plane function entity candidate list including at least one user plane function entity candidate entry, wherein each respective user plane function entity candidate entry of said candidate list comprises at least information on a private internet protocol address of the respective user plane function entity candidate and information on a public internet protocol address of said respective user plane function entity candidate, and selecting at least one user plane function entity from said user plane function entity candidate list.