skunz@iastate.edu (Kunz Steven L) (03/12/91)
Where can I find a document outlining the tn3270 protocol? I know that tn3270 uses the TCP-IP protocol as a transport medium - but what gets transported? Raw EBCDIC block-mode streams (as come over an IBM channel)? What about the "start up" protocol? It appears many micro tn3270 packages are in line mode until something in the protocol from the host kicks them into block mode. We've already checked for an RFC in the "nic" RFC repository - doesn't seem to be one. Does the protocol standard come out of IBM? Steve Kunz -- Iowa State University Computation Center
jbvb@FTP.COM (James B. Van Bokkelen) (03/15/91)
There is no document that defines TN3270 as such. The upper-layer HRRFC (1123) has a really basic explanation of block-mode Telnet, but that's all. There has never been an RFC because most of the community that uses it feels that it is inferior, and needs to be updated to reflect advances in IBM system software and terminal functions. RFC 1041 represents an attempt at this, but it has never been widely implemented. There is occasional discussion of revising it on "tn3270@terminus.umd.edu" and at IETFs. Here's a summary of the current protocol: Both Telnets agree on the Terminal Type option, then the client sends a terminal type of IBM327x-y (see RFCs 1091 and 1060). You may agree upon the Telnet EOR option, but there are implementations out there that don't, so don't insist. When you agree upon Telnet Binary, the data stream switches to EBCDIC, with 3270 command codes and AID bytes at the beginning of each block and buffer orders mixed with the data, using IAC EOR as end-of-block delimiter. If either side disables Telnet BInary, back to NVT until it is re-enabled. James B. VanBokkelen 26 Princess St., Wakefield, MA 01880 FTP Software Inc. voice: (617) 246-0900 fax: (617) 246-0901