Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!decvax!ucbvax!ACC.ARPA!art From: art@ACC.ARPA Newsgroups: comp.protocols.tcp-ip Subject: RE: X.25 Call User Data for higher level protocols Message-ID: <8802042313.AA26020@ucbvax.Berkeley.EDU> Date: 4 Feb 88 18:17:00 GMT Sender: usenet@ucbvax.BERKELEY.EDU Reply-To: Organization: The Internet Lines: 44 >I am in need of the protocol identifiers used in the CALL USER DATA >field of the X.25 CALL REQUEST packet for various higher level >protocols. I believe I know the following information but need to be >able to fill in the blanks. Can anyone help or provide a reference as >to where I might find this data? > >Who supplies these numbers? ISO? I would like to define an ID for a >virtual circuit that includes an extra 16 bit data field that could be >used like the ethernet type field. Has something like this already >been defined? Should I be using 802.2? Comments? > > Protocol Call User Data (byte in hex) > -------- -------------- > > PAD 0x01 > IP 0xCC > ISO IP 0xCD > XNS ?? > PUP ?? > DECNET ?? > Chaos ?? Greg, CCITT defines the high order two bits of the first octet of call user data as follows: 00 - Used for other CCITT recommendations (such as X.29) 01 - Reserved for use by "national" administrative authorities 10 - Reserved for use by international administative authorities 11 - Reserved for arbitrary use between consenting DTEs I believe (they can correct me if I'm wrong) that BBN chose 0xCC and 0xCD for use on the DDN. If you want to establish a standard for use in the Internet I would suggest contacting both DCA and ANSI to see if there is interest. I would appreciate hearing any results you find. Art Berggreen art@acc.arpa ------