Comments on: Chrome DNS Caching http://blog.ultranurd.net/2009/01/22/chrome-dns-caching/ Collected Commentary Fri, 16 Dec 2011 00:16:01 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Tom Lenz http://blog.ultranurd.net/2009/01/22/chrome-dns-caching/comment-page-1/#comment-6577 Tom Lenz Mon, 29 Mar 2010 03:41:52 +0000 http://blog.ultranurd.net/?p=494#comment-6577 I had to clear browsing data. (Wrench, options, under the hood) I had to clear browsing data. (Wrench, options, under the hood)

]]> By: Dan Crosta http://blog.ultranurd.net/2009/01/22/chrome-dns-caching/comment-page-1/#comment-1720 Dan Crosta Thu, 22 Jan 2009 21:37:07 +0000 http://blog.ultranurd.net/?p=494#comment-1720 In fact, many browsers cache DNS information, though not usually for more than a browsing session, as a way to reduce the number of DNS request they have to make. (Why the browsers cache this, rather than letting the system cache it, or why they don't obey the TTLs on DNS records is beyond me.) Andrew and I were looking into this the other day when learning about DNS SRV records, and whether it would be possible to have an SRV specify that HTTP should be reached on a port other than 80. Turns out the DNS protocol supports it, but no major browsers query SRVs. I suspect as a consequence, most sites do not list _tcp._http in their DNS SRV (because nobody asks for it). Chicken, meet egg. In fact, many browsers cache DNS information, though not usually for more than a browsing session, as a way to reduce the number of DNS request they have to make. (Why the browsers cache this, rather than letting the system cache it, or why they don’t obey the TTLs on DNS records is beyond me.)

Andrew and I were looking into this the other day when learning about DNS SRV records, and whether it would be possible to have an SRV specify that HTTP should be reached on a port other than 80. Turns out the DNS protocol supports it, but no major browsers query SRVs. I suspect as a consequence, most sites do not list _tcp._http in their DNS SRV (because nobody asks for it). Chicken, meet egg.

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