>
> On 3/7/2006 8:16 PM, Mark Andrews wrote:
>
> > * Hostnames that are 254 and 255 characters long cannot be
> > expressed in the DNS.
>
> Actually hostnames are technically defined with a maximum of 63 characters
> in total [RFC1123], and there have been some implementations of /etc/hosts
> that could not even do that (hence the rule).
RFC 1123
Host software MUST handle host names of up to 63 characters and
SHOULD handle host names of up to 255 characters.
63 is not a maximum. It is a minumum that must be supported.
> But even ignoring that rule (which you shouldn't, if the idea is to have a
> meaningful data-type), there is also a maximum length limit inherent in
> SMTP's commands which make the maximum practical mail-domain somewhat
> smaller than the DNS limit. For example, SMTP only requires maximum
> mailbox of 254 octets, but that includes localpart and @ separator. The
> relationship between these different limits is undefined within SMTP
> specs, but its there if you know about the inheritance.
>
> When it is all said and done, max practical application of mailbox address
> is 63 chars for localpart, "@" separator, 63 chars for domain-part.
> Anything beyond that runs afoul of one or more standards.
>
> </pedantry>
>
> --
> Eric A. Hall http://www.ehsco.com/
> Internet Core Protocols http://www.oreilly.com/catalog/coreprot/
>
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--
Mark Andrews, ISC
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PHONE: +61 2 9871 4742 INTERNET: Mark_Andrews@xxxxxxx
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