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I'm currently implementing a decentralized DNS, and am wondering if a domain name character limit is specific to the storage of DNS records

According to Wikipedia

The full domain name may not exceed a total length of 255 characters

But then below it also says

In practice, some domain registries may have shorter limits.

I've also looked at this answer here which mentions -

My understanding is that the 255-character limit is to be considered after the IDNA conversion.

This is because DNS records have this character limit...

Is this true, and if so, does this mean my implementation can resolve domains with larger than 256 chars?

Community
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liamzebedee
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  • Define "_resolve_" ? You make an authoritative server, recursive resolver, DNS client or what ? – Sandman4 Apr 28 '12 at 22:31
  • @Sandman4 I'm making an authoritative server, and in this context, resolve means to resolve the domain to the IP Address – liamzebedee Apr 29 '12 at 00:08

2 Answers2

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Thi is an RFC document you need: http://www.faqs.org/rfcs/rfc1035.html

According to this different DNS records has it's own limit.

Probably you shouldn't think about a particular software or different practices, you just should look to an appropriate document (rfc specification).

remort
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There are two limits:

  • 255 character total length - this is arbitrary "To simplify implementations" (section 3.1 of RFC 1035)

  • 63 characters per label - this is fixed by the 6 bit length field

There's nothing intrinsic in the wire format of DNS that limits names to 255 characters, but all DNS implementations should support up to that limit and no more.

Alnitak
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