Date: Mon, 18 Jan 2010 15:04:55 -0800 From: Chuck Swiger <cswiger@mac.com> To: Rink Springer <rink@FreeBSD.org> Cc: Jeff Roberson <jroberson@jroberson.net>, current@freebsd.org Subject: Re: Help test softupdates journaling (SUJ) Message-ID: <C4B1D6D6-4B8A-4410-99A8-E4E04F94B326@mac.com> In-Reply-To: <20100118221843.GB65074@rink.nu> References: <alpine.BSF.2.00.1001081456000.1027@desktop> <20100118175033.7ba10de0@ernst.jennejohn.org> <20100118165537.GG81608@camelot.theinternet.com.au> <20100118221843.GB65074@rink.nu>
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On Jan 18, 2010, at 2:18 PM, Rink Springer wrote: >> Because DNS hostnames can't contain underscores... ? > > That is false, they can (in fact, SVR records depend on this). However, > Jeff's blog is at http://jeffr-tech.livejournal.com/; his username > appears to be 'jeffr_tech'. Underscores appear in SRV records for the explicit purpose of not conflicting with any valid hostname: The format of the SRV RR Here is the format of the SRV RR, whose DNS type code is 33: _Service._Proto.Name TTL Class SRV Priority Weight Port Target Service The symbolic name of the desired service, as defined in Assigned Numbers [STD 2] or locally. An underscore (_) is prepended to the service identifier to avoid collisions with DNS labels that occur in nature. ...from http://www.ietf.org/rfc/rfc2782.txt. See http://www.ietf.org/rfc/rfc952.txt 1. A "name" (Net, Host, Gateway, or Domain name) is a text string up to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-), and period (.). ...which was slightly modified by http://www.ietf.org/rfc/rfc1123.txt 2.1 Host Names and Numbers The syntax of a legal Internet host name was specified in RFC-952 [DNS:4]. One aspect of host name syntax is hereby changed: the restriction on the first character is relaxed to allow either a letter or a digit. Host software MUST support this more liberal syntax. Regards, -- -Chuck
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