North American Network Operators Group
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Re: Underscores in host names

  • From: David Conrad
  • Date: Wed May 18 03:35:05 2005

Mark,

Grump.

I used to be in the 952/1123 sect, but I have since reformed and continue to do penance for my sins.

The "hostname is not a domain name" dodge is simply wrong. If you like, I can get a signed affadavit from the author of the DNS specifications (assuming he's in the office tomorrow) to the effect that it was always his intent that domain names be composed of any 8- bit value. That's the whole reason for length encoding the labels. RFC 2181, for all its other warts, explicitly clarified this particular issue.

The whole reason for check-names was because of very seriously broken software that would allow shell meta-characters in in-addr.arpa labels to do bad things. I have come to the opinion that if such software still exists, then the people who run that software deserve what they get. Check-names was a bad idea that might have been justified at the time, but pretending it remains justified by 952/1123 has got to stop sometime.

However, that rant was mostly irrelevant. Can you point to _ANY_ application, operating system, or anything else that has any issues whatsoever with an "_" of all characters?

Rgds,
-drc

On May 17, 2005, at 6:08 PM, Mark Andrews wrote:
    RFC 952 and RFC 1123 describe what is currently legal
    in hostnames.

    Underscore is NOT a legal character in a hostname.