DNS Client Cache Handling Expired Responses

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Solution Overview

Problem

The domain name system (DNS) architecture faces issues when DNS clients receive negative responses or no responses from DNS servers, leading to connection failures, particularly in mission-critical applications like telephony, where expired cached responses are flushed, causing service disruptions.

Innovation Solution

Implementing an enhanced DNS response caching mechanism that allows DNS clients to store and use expired cached responses until a positive response is received from the DNS server, using an optional parameter that enables continued use of cached responses beyond the Time to Live (TTL) value, ensuring connection completion without affecting TTL values or increasing query volume.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If DNS clients flush expired cached resolved domain names to maintain DNS accuracy, then DNS measurement precision is improved, but DNS reliability deteriorates because connection failures occur when DNS servers do not respond

Engineering Contradiction:

ImproveDNS resolution accuracyVSAvoidconnection success rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies dynamics by making the cache expiration behavior conditional rather than fixed. The DNS client dynamically adjusts its cache handling based on the enhanced DNS response caching parameter: when enabled, it uses expired cached responses; when disabled, it flushes them. This dynamic adaptation resolves the contradiction by allowing the system to maintain accuracy when needed while ensuring reliability when DNS servers are unresponsive.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of cache expiration behavior through the enhanced DNS response caching parameter. By toggling this parameter, the system can switch between two modes: traditional mode (flush expired cache) and enhanced mode (use expired cache). This parameter change allows the system to resolve the contradiction between measurement precision and reliability by selecting the appropriate behavior based on operational requirements.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If DNS clients use local caches to improve efficiency and reduce DNS traffic, then DNS productivity is improved, but DNS reliability deteriorates when cached responses expire and DNS servers are unavailable

Engineering Contradiction:

ImproveDNS resolution efficiencyVSAvoidconnection success rate

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent makes the cache usage behavior dynamic through the enhanced DNS response caching parameter. When the parameter is enabled, the DNS client dynamically continues using expired cached responses instead of immediately flushing them. This dynamic approach maintains productivity by keeping the cache functional while improving reliability by preventing connection failures during DNS server unavailability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies beforehand cushioning by allowing the DNS client to rely on expired cached responses as a buffer when DNS servers are unavailable. This cushioning mechanism prevents the harsh consequence of connection failures by providing a fallback option (expired cache) that maintains service continuity until the DNS server becomes available again.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If DNS clients send queries to refresh cached responses before TTL expiry, then DNS reliability is improved, but DNS loss of time increases due to additional query overhead

Engineering Contradiction:

Improveconnection success rateVSAvoidDNS query overhead time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies partial action by allowing the DNS client to use expired cached responses instead of requiring complete cache refreshes. When the enhanced DNS response caching parameter is enabled, the client can partially rely on expired cache data rather than performing the excessive action of sending refresh queries, thus reducing time loss while maintaining adequate reliability for many use cases.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11122138B2Enhanced domain name system response caching

Publication Date: 2021.09.14 CHARTER COMM OPERATING LLC

AI summary

Methods and systems for enhanced domain name system (DNS) response caching are described. An enhanced DNS response caching method includes receiving a connection request for a fully qualified domain name (FQDN). A DNS client checks a local cache for a cached resolved domain name corresponding to the FQDN and sends 3300 a query to obtain or refresh the cached resolved domain name if a Time to Live parameter is expired or about to expire. In response to receiving a negative response or no response for the query, the DNS client determines whether an enhanced DNS response caching parameter is enabled. If the enhanced DNS response caching parameter is enabled, the DNS client sends an expired cached resolved domain name to process the connection request.