RFC 2355 (rfc2355) - Page 2 of 38

TN3270 Enhancements

RFC 2355                  TN3270 Enhancements                  June 1998


          7.1.3 ASSOCIATE Command ................................. 12
          7.1.4 Accepting a Request ............................... 13
          7.1.5 REJECT Command .................................... 13
      7.2  FUNCTIONS Negotiation .................................. 14
          7.2.1 Commands .......................................... 14
          7.2.2 List of TN3270E Functions ......................... 16
   8.  TN3270E DATA MESSAGES ...................................... 16
      8.1  The TN3270E Message Header ............................. 18
          8.1.1 DATA-TYPE Field ................................... 18
          8.1.2 REQUEST-FLAG Field ................................ 19
          8.1.3 RESPONSE-FLAG Field ............................... 19
          8.1.4 SEQ-NUMBER Field .................................. 20
   9.  BASIC TN3270E .............................................. 20
      9.1  3270 Mode and NVT Mode ................................. 21
   10. DETAILS OF PROCESSING TN3270E FUNCTIONS .................... 22
      10.1 The SCS-CTL-CODES Function ............................. 22
      10.2 The DATA-STREAM-CTL Function ........................... 23
      10.3 The BIND-IMAGE Function ................................ 24
      10.4 The RESPONSES Function ................................. 25
         10.4.1 Response Messages ................................. 26
      10.5 The SYSREQ Function .................................... 28
         10.5.1 Background ........................................ 28
         10.5.2 TN3270E Implementation of SYSREQ .................. 29
   11. THE 3270 ATTN KEY .......................................... 30
   12. 3270 STRUCTURED FIELDS ..................................... 31
   13. IMPLEMENTATION GUIDELINES .................................. 31
      13.1 3270 Data Stream Notes ................................. 31
      13.2 Negotiation of the TN3270E Telnet Option ............... 32
      13.3 A "Keep-alive" Mechanism ............................... 32
      13.4 Examples ............................................... 32
   14. SECURITY CONSIDERATIONS .................................... 36
   15. REFERENCES ................................................. 36
   16. AUTHOR'S NOTE .............................................. 37
   17. AUTHOR'S ADDRESS ........................................... 37
   18. Full Copyright Statement ................................... 38

1.  Introduction

   Traditionally, support for 3270 terminal emulation over Telnet has
   been accomplished by the de facto standard of negotiating three
   separate Telnet Options - Terminal-Type [2], Binary Transmission [3],
   and End of Record [4].  Note that there is no RFC that specifies this
   negotiation as a standard.  RFC 1041 attempted to standardize the
   method of negotiating 3270 terminal support by defining the 3270
   Regime Telnet Option.  Very few developers and vendors ever
   implemented RFC 1041.





Kelly                       Standards Track