python · miss-islington · Feb 24, 2020 · Feb 24, 2020
@@ -439,6 +439,17 @@ Opening network connections

      Added the *happy_eyeballs_delay* and *interleave* parameters.

+      Happy Eyeballs Algorithm: Success with Dual-Stack Hosts.
+      When a server's IPv4 path and protocol are working, but the server's
+      IPv6 path and protocol are not working, a dual-stack client
+      application experiences significant connection delay compared to an
+      IPv4-only client.  This is undesirable because it causes the dual-
+      stack client to have a worse user experience.  This document
+      specifies requirements for algorithms that reduce this user-visible
+      delay and provides an algorithm.
+
+      For more information: https://tools.ietf.org/html/rfc6555
+
   .. versionadded:: 3.7

      The *ssl_handshake_timeout* parameter.