http://www.rfc-editor.org/rfc/rfc0855.txt
RFC 0855: Telnet Option Specifications, J. Postel, J.K. Reynolds1983-05-01T23:00:00-00:00This memo specifies the general form for Telnet options and the directions for their specification. This RFC specifies a standard for the ARPA Internet community. Hosts on the ARPA Internet are expected to adopt and implement this standard. Obsoletes RFC 651, NIC 18640.