Re: [DNSOP] Minor editorial change to draft-ietf-dnsop-sutld-ps

John C Klensin <> Thu, 06 July 2017 18:04 UTC

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Date: Thu, 06 Jul 2017 14:04:10 -0400
From: John C Klensin <>
To: Mark Andrews <>, "Roy T. Fielding" <>
cc: dnsop <>, IETF Rinse Repeat <>
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Subject: Re: [DNSOP] Minor editorial change to draft-ietf-dnsop-sutld-ps
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--On Thursday, July 6, 2017 09:11 +1000 Mark Andrews
<> wrote:

> And the actual presentation limit for LDH with DNS is 253
> (encodes as 255 octets on the wire).  Remember URI names do
> not have a final period and the each label has length octet
> when encoded as a DNS name and the name is terminated by the
> root label (0x00) in DNS wire form and the DNS wire name is
> limited to 255 octets.


My apologies for nit-picking, but RFC 3986, Section 3.2.2 is
quite clear than DNS names in URIs are permitted to have a final
period and encouraged to do so under some circumstances.

	"The rightmost domain label of a fully qualified domain
	name in DNS may be followed by a single "." and should
	be if it is necessary to distinguish between the
	complete domain name and some local domain."

I don't think that changes the 253 octet limit, but the comment
about URIs is misleading and could contribute to an, IMO,
already high level of confusion about what RFC 3986 does or does
not specify.

The same subsection of RFC 3986 also uses the term "host
subcomponent" for what you are referring to as a name and allows
it to be a "registered name" (or <reg-name>) that might not be a
DNS name or reference at all -- whether it is or not is