在「PChome 24h 連線會慢的原因...」這篇的 comment 有讀者提到了 Happy Eyeballs 應該可以解決這個問題：
除了可以在維基百科上面看到外，比較正式的說明可以參考 RFC 6555：「Happy Eyeballs: Success with Dual-Stack Hosts」，其中在「6. Example Algorithm」就有提到 Google Chrome 與 Mozilla Firefox 怎麼實做 Happy Eyeballs：
What follows is the algorithm implemented in Google Chrome and Mozilla Firefox.
- Call getaddinfo(), which returns a list of IP addresses sorted by the host's address preference policy.
- Initiate a connection attempt with the first address in that list (e.g., IPv6).
- If that connection does not complete within a short period of time (Firefox and Chrome use 300 ms), initiate a connection attempt with the first address belonging to the other address family (e.g., IPv4).
- The first connection that is established is used. The other connection is discarded.
If an algorithm were to cache connection success/failure, the caching would occur after step 4 determined which connection was successful.
Other example algorithms include [Perreault] and [Andrews].
可以看到 Happy Eyeballs 的演算法是要避免 IPv6 network 不通的情況卡住很慢 (如果在 300ms 內連線沒有建起來，就會儘快往另外一個 address family 嘗試)，而不是在 DNS 層避免問題 (也就是 getaddinfo() 觸發的 DNS query)。
這次的情況是 DNS query 很慢，就會導致還是一開始就很慢，Happy Eyeballs 沒辦法解決這個問題。
不過話說回來，我是有印象知道有這個演算法，但不知道有「Happy Eyeballs」這個這麼逗趣的名字... (掩面)
