IDNs are domain names represented by local language characters. Such domain names could contain characters with diacritical marks as required by many European languages, or characters from non-Latin scripts (for example, Arabic or Chinese). IDNs make the domain name label as it is displayed and viewed by the end user different from that transmitted in the DNS. To avoid confusion the following terminology is used: The A-label is what is transmitted in the DNS protocol and this is the ASCII-compatible (ACE) form of an IDNA string; for example "xn--11b5bs1di". The U-label is what should be displayed to the user and is the representation of the Internationalized Domain Name (IDN) in Unicode; Lastly, the LDH-label strictly refers to an all-ASCII label that obeys the "hostname" (LDH) conventions and that is not an IDN.
