The IAB welcomes the opportunity to comment on "Guidelines for the Implementation of Internationalized Domain Names" (https://www.icann.org/en/system/files/files/draft-idn-guidelines-03mar17-en.... <https://www.icann.org/en/system/files/files/draft-idn-guidelines-03mar17-en....>) As a general observation, the IAB found this document to be a good step in support of the deployment of Internationalized Domain Names in TLDs. It promotes the use of IDNs while also supporting careful specification and conservative implementation of registry and registrar policy. A few specific comments follow: Section 1.1: This is worded so that the document relies upon RFC 2119 keywords ("must," "should") but it is not, strictly speaking, a protocol document. It might be helpful to clarify that this normative language defines what it means to comply with these guidelines, but can't by itself specify protocol compliance. Section 2.1: The clear statement of support for compliance with IDNA2008 standard as a target, while also supporting a clean transition from other specifications, also seems appropriately conservative. Section 2.2 and 2.3: These sections aknowledge implicitly that there isn't always a good answer, that sometimes various combinations of a language and a script, or of possible variants, are not fully compatible across all the options and the registry simply has to make a decision. It might be helpful to state as much explicitly. Sec. 2.4, subsection 13, final paragraph: this is a sentence fragment, and not entirely clear. Is it meant as an example of the references appropriate for review to meet the guideline in the previous paragraphs for registry-side processing for IDN variants? Overall, Sec. 2.2-2.5 seem to provide a reasonable balance between clear guidance and discretion for TLDs trying to form IDN policies that support their user communities. Sec. 2.2-2.5 in the document seems to be trying to operationalize the provisions in RFC 5894 that registries have a policy and that they allow only those characters whose use they fully understand, but without quite stating that as the goal. A few words clarifying that point might help both ICANN and TLD operators in cases where it's not entirely clear how best to follow the guidelines. Respectfully submitted, Suzanne Woolf for the IAB