TN3270 Enhancements
RFC 2355

Document Type RFC - Draft Standard (June 1998; No errata)
Updated by RFC 6270
Obsoletes RFC 1647
Last updated 2013-03-02
Stream IETF
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IESG IESG state RFC 2355 (Draft Standard)
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Network Working Group                                           B. Kelly
Request for Comments: 2355                             Auburn University
Obsoletes: 1647                                                June 1998
Category: Standards Track

                          TN3270 Enhancements

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   This document describes a protocol that more fully supports 3270
   devices than do traditional tn3270 practices.  Specifically, it
   defines a method of emulating both the terminal and printer members
   of the 3270 family of devices via Telnet; it provides for the ability
   of a Telnet client to request that it be assigned a specific device-
   name (also referred to as "LU name" or "network name"); finally, it
   adds support for a variety of functions such as the ATTN key, the
   SYSREQ key, and SNA response handling.

   This protocol is negotiated under the TN3270E Telnet Option, and is
   unrelated to the Telnet 3270 Regime Option as defined in RFC 1041
   [1].

TABLE OF CONTENTS

   1.  Introduction ...............................................  2
      1.1  Changes to RFC 1647 ....................................  4
   2.  TN3270E OVERVIEW ...........................................  5
   3.  COMMAND NAMES AND CODES ....................................  6
   4.  COMMAND MEANINGS ...........................................  7
   5.  DEFAULT SPECIFICATION ......................................  9
   6.  MOTIVATION .................................................  9
   7.  TN3270E SUB-NEGOTIATION RULES ..............................  9
      7.1  DEVICE-TYPE Negotiation ................................  9
          7.1.1 Device Pools ...................................... 10
          7.1.2 CONNECT Command ................................... 12

Kelly                       Standards Track                     [Page 1]
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
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