Keep this document to one review outcome: Race IPv6 and IPv4 connection attempts from one interleaved candidate list. Only the official source and traced locations below supply facts. Confirm applicability before acting.
\nThe official RFC 8305 — Happy Eyeballs Version 2: Better Connectivity Using Concurrency from RFC Editor / Internet Engineering Task Force supports the following bounded statements:
\nOnly the traced statements above are asserted as source facts. Apply the review to address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains after confirming that the source and deployed context match.
\nThis RFC evidence supports only the named network-protocol decision; it does not select vendor settings, topology, capacity, or an acceptable failure mode. A correct source interpretation can still be inapplicable to a particular design. Confirm DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring, ownership, and change authority instead of treating documented behavior as a deployment guarantee.
\nDSE recommends using the cited source as the evidence anchor for this decision. Begin by recording scope and current state before deciding whether a change is warranted. Record the source location, examined part of address plans, interfaces, routes, peers, protocol roles, timers, middleboxes, and intended failure domains, observed and expected states, owner, and reason for deviation.
\nAn implementation decision needs an owner, approved window, prechecks, observable outcome, stop authority, and rollback path. Validate DNS, Active Directory authentication, PKI, time, routing policy, transport reachability, and monitoring before and after the test, and store only sanitized operational evidence.
\nBuild a reproducible chain from Section 3 (Hostname Resolution Query Handling); Section 4 (Sorting Addresses); Section 5 (Connection Attempts) to the observed environment. Useful domain evidence includes configuration snapshots, route or neighbor state, packet captures, counters, topology records, and controlled failover results; label every item with scope, timestamp, collector, and stable identifier.
\nRecord the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.
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