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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> regext [mailto:regext-bounces@ietf.org]
<b>On Behalf Of </b>Gustavo Lozano<br>
<b>Sent:</b> Thursday, April 14, 2016 3:16 PM<br>
<b>To:</b> regext; gtld-tech@icann.org<br>
<b>Subject:</b> [regext] A-label and U-label mixing - RDAP query<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:black">Hello colleagues,</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Apologies for crossposting.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">During the public comments period of the "Registration Data Access Protocol (RDAP) Operational Profile for gTLD Registries and Registrars",
<a href="https://www.icann.org/public-comments/rdap-profile-2015-12-03-en">https://www.icann.org/public-comments/rdap-profile-2015-12-03-en</a>, the following comment was received:</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><i><span style="color:black">"Section 1.4.1 of the Operational Profile is inconsistent with the guidance given in RFC 7482 regarding processing of RDAP queries containing a mixture of IDN A-labels and U-labels. Per RFC 7482, “IDNs SHOULD
NOT be represented as a mixture of A-labels and U-labels; that is, internationalized labels in an IDN SHOULD be either all A-labels or all U-labels”. This requirement is not only inconsistent with RFC 7482, it is also counter to the consensus of the IETF community
regarding appropriate processing of IDN queries. "</span></i><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">Another comment on the same path says:</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><i><span style="color:black">"Allowing A-labels and U-labels will be particularly unworkable for right to left languages unless the RDAP server introduces arbitrary restrictions. It is important to remember that RDAP is intended for machine-to-machine
communication. Since RFC 7482 is very clear on this guidance (do not mix the two) any software client that generates this sort of query is broken. With the relative youth of the RDAP standard there is unlikely to be a large install base of software clients
with said broken implementation. If ICANN is aware of a software client that has incorrectly implemented the RDAP standard and is now generating queries which combine A-labels and U-labels then ICANN should take its concerns to the IETF where such challenges
are considered as part of any implementation discussion. Enshrining bad practice within the Operational Profile will result in needless future changes to the technology or additional service restrictions."</span></i><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:black">The comment is related to the following section of the gTLD RDAP profile:</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><i><span style="color:black">"1.4.1 The RDAP server MUST support Internationalized Domain Name (IDN) RDAP lookup queries using A-label or U-label format [RFC 5890] for domain name and name server objects. The RDAP server MUST accept a mixture
of the two (i.e. A-label and U-label format) in the same RDAP lookup query”. </span>
</i><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">The purpose of this message is to obtain feedback from this community regarding this issue. We believe that the following text from RFC 7482 is a requirement for the RDAP client:
<i>"IDNs SHOULD NOT be represented as a mixture of A-labels and U-labels; that is, internationalized labels in an IDN SHOULD be either all A-labels or all U-labels.".</i></span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">RFC7482 provides an example of why a server may receive a mixture of A-labels and U-labels in the query:
<i>"It is possible for an RDAP client to assemble a query string from multiple independent data sources. Such a client might not be able to perform conversions between A-labels and U-labels."</i></span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">RFC7482 gives two options to the server:
<i>"An RDAP server that receives a query string with a mixture of A-labels and U-labels MAY convert all the U-labels to A-labels, perform IDNA processing, and proceed with exact-match lookup. In such cases, the response to be returned to the query source may
not match the input from the query source. Alternatively, the server MAY refuse to process the query".</i></span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"> </span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">We believe that the reasoning in RFC 7482 is sufficient to require gTLD RDAP servers to accept and process a query that mixes A-labels and U-labels.</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal">Question for this community: is the behavior specified in the gTLD RDAP Profile (I.e. requiring processing of queries that mixes A-labels and U-labels) consistent with RFC 7482?<o:p></o:p></p>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">I am the editor of the text that appears in RFC 7482. It was written to reflect guidance we received from Andrew Sullivan, John Klensin, and others – it may be worth asking them directly if they’re not still
following along. It was also discussed during the IESG review. This wasn’t an easy topic to wade through.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Having said that, I do believe that the profile requirement that a server MUST support mixed-label lookups is inconsistent with RFC 7482. The text in Section 3.1.3 is clear on the guidance to server operators.
As you quoted above:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">“An RDAP server that receives a query string with a mixture of A-labels and U-labels MAY convert all the U-labels to A-labels, perform IDNA processing, and proceed with exact-match lookup. In such cases, the
response to be returned to the query source may not match the input from the query source. Alternatively, the server MAY refuse to process the query.”<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">The RFC says that the server operator can choose which action to perform: convert to all A-labels and process, or refuse to process. Processing a mixture of the label forms isn’t one of the available options.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Scott</span><span style="color:#1F497D"><o:p></o:p></span></p>
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