DNS Resolution in 5G UEs via Selective Cache Flush
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Solution Overview
Problem
Current 5G systems face challenges in efficiently initiating DNS resolution, particularly in scenarios where user equipment (UE) moves between different cells or geographic locations, leading to changes in local DNS IP addresses and Data Network Access Identifiers, which can result in suboptimal DNS cache management and re-resolution processes.
Innovation Solution
The proposed solution involves the Session Management Function (SMF) detecting changes in the UE's location and sending a DNS re-resolution indication to the UE via a non-access stratum (NAS) session management message, including a list of fully qualified domain names (FQDNs) or DNS suffixes, prompting the UE to initiate a selective DNS flush and re-resolution for affected PDU sessions, thereby optimizing DNS re-resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE maintains DNS cache for all PDU sessions, then DNS lookup efficiency is improved, but DNS accuracy deteriorates when UE moves between network areas with different local DNS IP addresses
Solution Approach 1:
The patent segments the DNS cache management by PDU session, allowing the UE to maintain separate DNS cache entries for different PDU sessions. This enables selective flushing of DNS records for specific PDU sessions when the UE moves between network areas, rather than flushing all DNS caches globally. The SMF sends re-resolution indications targeted at specific PDU sessions, and the UE selectively flushes and re-resolves DNS records only for affected sessions, maintaining accuracy while preserving cache efficiency.
2Reliability
If the UE performs full DNS re-resolution when moving between cells, then DNS resolution accuracy is improved, but network signaling overhead and latency increase
Solution Approach 1:
The patent applies local quality by making DNS cache management decisions specific to each PDU session based on local network conditions. When the UE moves between cells, the SMF determines which specific PDU sessions are affected by the location change and sends re-resolution indications only for those sessions. The UE then performs selective DNS flushing and re-resolution only for the affected PDU sessions, rather than performing a global flush. This localized approach maintains DNS accuracy for affected sessions while minimizing unnecessary re-resolution overhead.
3Reliability
If the network sends frequent DNS re-resolution indications to moving UEs, then DNS resolution accuracy is improved, but network signaling overhead increases
Solution Approach 1:
The patent implements partial action by sending DNS re-resolution indications selectively rather than universally. The SMF evaluates each UE's movement and determines which specific PDU sessions require re-resolution based on the local DNS IP address changes. Re-resolution indications are sent only for those specific sessions where the local DNS has changed, rather than sending indications for all PDU sessions. This partial approach maintains DNS accuracy where needed while reducing unnecessary signaling overhead.
Data Source
AI summary
An apparatus used in a UE includes processing circuitry and memory. To configure the UE for a DNS resolution, the processing circuitry is to encode UL data for transmission to a first EAS via a first data path. The first data path includes a first UL CL UPF and a first PSA. A NAS SM message received from an SMF node is decoded. The NAS SM message includes an EAS rediscovery indication and a list of FQDNs associated with the first EAS. A DNS resolution procedure with a DNS server is performed in response to the EAS rediscovery indication, to obtain an IP address of a second EAS. The DNS resolution procedure is based on the list of FQDNs, and a second data path to the second EAS is established based on the IP address.