FQDN

[Nico Kadel-Garcia]

phn at icke-reklam.ipsec.nu wrote:

> phaniraj ranganath <hrphani at yahoo.co.in> wrote:
> 
>>Hello,
>>  I want to know why the FQDN cann't be more than 256 characters &
>>the name at any node in Internet Domain name space cann't be more than 63 characters?
>>Is there any restriction in the number of levels in Internet i.e. from root servers how many levels can the structure of internet span?
>> 
>>thanking u,
>>phani
>>SMS using the Yahoo! Messenger;Download latest version.
> 
> 
> This limitations comes from the standard ( RFC1035 ) and also by the
> implementation ( since most implementations are compliant)

And there are good reasons for it. DNS is old, from a time when memory 
was much more expensive. Doubling the maximum possible length would have 
meant doubling sizes for quite a lot of data, which can otherwise be 
stored pretty damn efficiently. Even now, doubling the maximum name 
length could cause some *serious* absurdities by encouraging some damned 
silly manipulations of hostnames.

Heck, there are DNS implementations that cannot deal with non-qualified 
hostnames of more than 15 characters. (Certain Windows implementations).