"Introduction IDNA2008 This document is one of a collection that@ together@ describe the protocol and usage context for a revision of Internationalized Domain Names for Applications (IDNA) that was largely completed in 2008@ known within the series and elsewhere as ""IDNA2008"". The series replaces an earlier version of IDNA [RFC3490] [RFC3491]. For convenience@ that version of IDNA is referred to in these documents as ""IDNA2003"". The newer version continues to use the Punycode algorithm [RFC3492] and ACE (ASCII-compatible encoding) prefix from that earlier version. The document collection is described in Section 1.2. As indicated there@ this document provides definitions and other material that are common to the set."