JBVB@AI.AI.MIT.EDU.UUCP (06/27/87)
"TN3270" is a specialized mode of Telnet, entered once receptive hosts (IBM MVS or VM systems) have negotiated the TERMINAL_TYPE option, requested and received a terminal type of IBM-3278-2 (or another 3270-type terminal agreeable to both ends), and negotiated the EOR and BINARY options (some hosts are satisfied with just BINARY). Once you are in 3270 mode, the data stream shifts to EBCDIC, and EOR is used to define the boundaries of of blocks of data (Write commands, responses to Read & Read-Modified, and AID sequences, with or without trailing modified fields). The server disables whatever translation or emulation it was using initially, and passes the 3270 data stream to its applications (while still filtering IAC xxx). The client gets the 3270 orders, and either translates them into something suitable for the user's display (and vice versa), or passes them on to a locally- connected 327x (if the client is another IBM mainframe). If BINARY is re-negotiated and turned off, the data stream returns to NVT ascii. Implementations that I am sure support TN3270 include: UCLA MVS ACP client & server ACC ACCESS/MVS client & server Spartacus KNET/MVS client & server WISCNET VM client & server IBM VM client & server (old Wiscnet, & recent announcement) Spartacus KNET/VM client & server ACC ACCESS/VM client & server 4BSD (G. Minshall) client (source form, usable on most 4BSD derivatives) FTP Software PC/TCP client (MS/DOS IBM-compatible PCs only) In addition, Greg Minshall has mentioned an adaptation of his software to the Ungermann-Bass NIU card on the PC, and there may be other academic efforts available. Other mainframe software vendors *may* be able to support TN3270, ask them. IBM has announced an MS/DOS TCP/IP for PCs, which includes a TN3270 client, sheduled for availability 7/31. As of this moment, the only written information I am aware of would be found in the archives of the tcp-ip mailing list, dating from January through March of this year. An effort is in progress to write an RFC on TN3270, organized by Bruce Crabill (bruce@umdd.umd.edu), but I haven't seen any working documents yet. jbvb@ai.ai.mit.edu James B. VanBokkelen FTP Software Inc.