lost and found ( for me ? )

DNS プリフェッチ

DNS Prefetching



Google Chrome , Firefox は DNS Prefetch を使ってるみたい。
IE は使ってないみたい。

- Google

DNS resolution time can lead to a significant amount of user perceived latency. The time that DNS resolution takes is highly variable. Latency delays range from around 1ms (locally cached results) to commonly reported times of several seconds.

DNS prefetching is an attempt to resolve domain names before a user tries to follow a link. This is done using the computer's normal DNS resolution mechanism; no connection to Google is used. Once a domain name has been resolved, if the user does navigate to that domain, there will be no effective delay due to DNS resolution time. The most obvious example where DNS prefetching can help is when a user is looking at a page with many links to various domains, such as a search results page. When we encounter hyperlinks in pages, we extract the domain name from each one and resolving each domain to an IP address. All this work is done in parallel with the user's reading of the page, using minimal CPU and network resources. When a user clicks on any of these pre-resolved names, they will on average save about 200 milliseconds in their navigation (assuming the user hadn't already visited the domain recently). More importantly than the average savings, users won't tend to experience the "worst case" delays for DNS resolution, which are regularly over 1 second.

- Firefox

では、Chrom で www.yahoo.co.jp を参照したときのクエリ量を比較~。

DNS Prefetch ありだと、152クエリも出してるー。

無効にすると、20 クエリになった。

すごい Prefetch 有効だと、無効にくらべ、7.5倍もクエリが。( サイトにリンク先の数に依存するけど )
リンク先たどると、確かに有効にした方が早い気がするなー。( 定量的ではなく、体感 ^^; )

いずれ、IEも DNS Prefech いれるのかなー。。。
個人的には Chrome > Firefox >>>> IE って感じるけど、ブラウザの高速化に寄与する部分として、DNS Prefetch による効果ってどのくらいの

サーバ側で、Prefech の制御ができるみたい。

DNS Prefetch Control

prefetch を無効にする方法。( デフォルトは有効 )

Thx for droppin' by n' Cheers!

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