Joe Touch wrote: > Seems clear to me: > > RFC1035: > > The labels must follow the rules for ARPANET host names. They must > start with a letter, end with a letter or digit, and have as interior > characters only letters, digits, and hyphen. There are also some > restrictions on the length. Labels must be 63 characters or less. That is syntax in section "2.3.1. Preferred name syntax" as syntax preferred by applications that use host names. The following syntax will result in fewer problems with many applications that use domain names (e.g., mail, TELNET). The basic rule of the RFC is: Although labels can contain any 8 bit values in octets that make up a label A label may include '.' character as is, as there is no escape mechanism, though applications expecting host names may fail to recognize it. Masataka Ohta