Is there a maximum allowed subdomain depth supported by webservers or browsers?
For example, could a domain like foo.bar.baz.monkey.pirate.google.com cause problems?
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There is no defined maximum in terms of the number of dot-delimited subdomains, but DNS does limit the maximum overall length of a hostname (including the dots) to 255 characters.
Due to rfc1035:
To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less.
Each label is represented as a one octet length field followed by that number of octets. Since every domain name ends with the null label of the root, a domain name is terminated by a length byte of zero
So, maximum valid length is 255-2 symbols (tested in DIG). Whole UDP message also should be less or equal 512 bytes. But that's not too small and makes IPoverDNS possible.