I think these words in section 18.104.22.168 of draft-ietf-ipp-implementers-guide-00.txt need to be changed as a result of late-breaking changes to MOD:
client-error-charset-not-supported: the charset supplied in the "attributes-charset" operation attribute is not supported. The Printer's "configured-charset" MUST be returned in the response as the value of the "attributes-charset" operation attribute and used for any 'text' and 'name' attributes returned in the error response. This error SHOULD take precedence over any other error, unless the request syntax is so bad that the client's supplied "attributes-charset" cannot be determined.
See the original message at http://www.egroups.com/list/ipp/?start=4900