2007-08-30 N/A Not assigned by IANA ITU-T TSB defines the high order two bits of the first octet of call user data as follows: 00 - Used for other ITU-T TSB recommendations (such as X.29) 01 - Reserved for use by "national" administrative authorities 10 - Reserved for use by international administrative authorities 11 - Reserved for arbitrary use between consenting DTEs 01 PAD C5 Blacker front-end descr dev CC IP ISO SC6/WG2 approved assignment in ISO 9577 (January 1990). CD ISO-IP CF PPP DD Network Monitoring Alain Lanssiers mailto:alanssie&cisco.com