rfc1647.txt

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      another device-type after the server has sent a DEVICE-TYPE
      REJECT command (see below).  This command requests emulation of
      a specific 3270 device type and model.  The REQUEST command may
      optionally include either the CONNECT or the ASSOCIATE command
      (but not both).  If present, CONNECT and ASSOCIATE must both be
      followed by <device-name>.  (See the section entitled
      "DEVICE-TYPE Negotiation" for more detailed information.)

   IAC SB TN3270E DEVICE-TYPE IS <device-type> CONNECT
          <device-name> IAC SE

      Only the server may send this command.  This command is used to
      accept a client's DEVICE-TYPE REQUEST command and to return the
      server-defined device-name.

   IAC SB TN3270E DEVICE-TYPE REJECT REASON <reason-code> IAC SE

      Only the server may send this command.  This command is used to
      reject a client's DEVICE-TYPE REQUEST command.

   IAC SB TN3270E FUNCTIONS REQUEST <function-list> IAC SE

      Either side may send this command.  This command is used to
      suggest a set of 3270 functions that will be supported on this
      session.  It is also sent as an implicit rejection of a previous
      FUNCTIONS REQUEST command sent by the other side (see the
      section entitled "FUNCTIONS Negotiation" for more information).
      Note that when used to reject a FUNCTIONS REQUEST command, the
      function-list must not be identical to that received in the
      previous REQUEST command.

   IAC SB TN3270E FUNCTIONS IS <function-list> IAC SE

      Either side may send this command.  This command is sent as a
      response to a FUNCTIONS REQUEST command and implies acceptance
      of the set of functions sent to it in the REQUEST command.  Note
      that the list of functions in the FUNCTIONS IS command must
      match the list that was received in the previous FUNCTIONS
      REQUEST command.

5.  Default Specification

   WON'T TN3270E

   DON'T TN3270E

   i.e., TN3270E will not be used.




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6.  Motivation

   See the section entitled "Introduction".

7.  TN3270E Sub-negotiation Rules

   All TN3270E commands and parameters are NVT ASCII strings in which
   upper and lower case are considered equivalent.

   Once it has been agreed that TN3270E will be supported, the first
   sub-negotiation must concern the DEVICE-TYPE (and possibly DEVICE-
   NAME) information.  Only after that has been successfully negotiated
   can the client and server exchange FUNCTIONS information.  Only after
   both DEVICE-TYPE and FUNCTIONS have been successfully negotiated can
   3270 data stream transmission occur.

   7.1 DEVICE-TYPE Negotiation

      Device-type (and device-name) negotiation begins when the server
      transmits the DEVICE-TYPE SEND command to the client.  The client
      responds with the DEVICE-TYPE REQUEST command, which must include
      a device-type and may include a device-name request.

      Valid device-types are:

       terminals: IBM-3278-2  IBM-3278-2-E  (24 row x 80 col display)
                  IBM-3278-3  IBM-3278-3-E  (32 row x 80 col display)
                  IBM-3278-4  IBM-3278-4-E  (43 row x 80 col display)
                  IBM-3278-5  IBM-3278-5-E  (27 row x 132 col display)
                  IBM-DYNAMIC            (no pre-defined display size)

        printers: IBM-3287-1

      Note that the use of '3278' and '3287' is NOT intended to exclude
      any particular device capabilities; they are used here only
      because they are commonly known designations for a terminal and a
      printer member of the 3270 family of devices.  The intention is to
      simplify the device-type negotiation (in comparison to traditional
      tn3270) by minimizing the number of possible device-types, and by
      breaking the association of a specific piece of IBM hardware with
      a related set of data stream capabilities.  For example,
      negotiation of device-type IBM-3278-2-E does NOT in and of itself
      preclude the use of any of the functions associated with a
      physical 3279 model S2B.  A client's ability to support the more
      advanced functions of the 3270 data stream will be indicated not
      by negotiation of an IBM device type and model number, but rather
      by the combination of Read Partition Query and Query Reply.




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      All of the terminal device-types support a "primary" display size
      of 24 rows by 80 columns.  The "-3", "-4" and "-5" types each
      support an "alternate" display size as noted in the above list.
      The IBM-DYNAMIC device-type implies no pre-defined alternate
      display size; this value will be passed from the client to host
      applications as part of the Query Reply structured field, and it
      can represent any display size the client and the host application
      can support.

      Terminal device-types with the "-E" suffix should only be
      negotiated by clients that are willing to support some subset of
      the 3270 "extended data stream".  This usually includes at a
      minimum support for extended colors and highlighting, but may also
      include a number of other functions, such as graphics capability,
      alternate character sets, and partitions.

      Clients that negotiate a terminal device-type with the "-E" suffix
      or the DYNAMIC type, as well as those that negotiate a printer
      device-type, must be able to accept and respond to a Read
      Partition Query command (see the section entitled "3270 Structured
      Fields").  This allows the client to indicate to host applications
      which subsets of the 3270 extended data stream the client is
      willing to support.

      In a VTAM/SNA environment, negotiation of IBM-DYNAMIC as the
      device-type should result in a Bind in which the Presentation
      Services Usage screen field (the eleventh byte in the logmode's
      PSERVIC field) is set to 0x03, indicating that the alternate
      screen size will be determined by the Query Reply (Usable Area)

      7.1.1 Device Pools

         An explanation of the CONNECT and ASSOCIATE commands first
         requires a discussion of the organization of terminal and
         printer device pools that the server maintains and from which
         it selects device-names to assign to session requests.  (The
         terms "device-name", "LU name" and "network name" can be
         considered interchangeable in this document.)  Also, for the
         purposes of this discussion, the term "generic session request"
         will be used to describe a request for a session by a Telnet
         client (either traditional or TN3270E) that does not include a
         request for a specific device-name.  The term "specific session
         request" will be used to describe a request for a session by a
         TN3270E client that includes a request for a specific device-
         name (either via CONNECT or ASSOCIATE).

         As is the case with traditional tn3270, the TN3270E server must
         maintain a set of terminal device-names.  A generic request for



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         a terminal session would result in the server selecting any
         available device-name from this pool.  The server, however, may
         also maintain a separate pool of terminal device-names which
         can only be used to satisfy specific terminal session requests.
         This is to ensure that a terminal device that has some
         significance to host applications (and is therefore likely to
         be the target of a specific session request) is not
         "accidentally" assigned to a generic request and winds up
         associated with a client that has no use for it.  Note that the
         reverse situation is allowed.  That is, a specific terminal
         session request could ask for a device-name that happens to be
         in the "generic terminal pool".

         For each terminal device (in both the "generic" and the
         "specific" pools), the TN3270E server could also have defined a
         "partner" or "paired" printer device.  There should be a
         unique, one-to-one mapping between a terminal and its
         associated printer.  The reasoning behind such a configuration
         is to allow for those host applications that produce printed
         output bound for a printer whose device-name is determined by
         the device-name of the terminal that initiated the print
         request.  These printer devices can only be assigned to
         specific printer session requests that use the ASSOCIATE
         command (see below).

         In addition, the TN3270E server may also maintain a pool of
         printer device-names that are not associated with any terminal.
         These printer devices can only be assigned to specific printer
         session requests that use the CONNECT command (see below).
         This allows for those host applications that generate printed
         output bound for a printer whose device-name is determined by
         something other than the device-name of the terminal that
         initiated the print request (for example, when the userid of
         the person signed on to a terminal determines the print
         destination).

         Finally, it is possible that a pool of printer device-names
         could be maintained and used only to satisfy generic requests
         for printers.

      7.1.2 CONNECT Command

         CONNECT is used by the client to request that the server assign
         a specific device-name to this Telnet session; it may be used
         when requesting either a terminal or a printer session.  The
         specified device-name must not conflict with the device-type;
         e.g., if the client requests DEVICE-TYPE IBM-3287-1 (a printer)
         and specifies CONNECT T1000001, but T1000001 is defined at the



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         host as a terminal, then the server should deny the request.
         Further, if the requested device-name is already associated
         with some other Telnet session, or if it is not defined to the
         server, the server should deny the request.

      7.1.3 ASSOCIATE Command

         ASSOCIATE can be used by the client only when requesting a
         DEVICE-TYPE that represents a printer. The ASSOCIATE command
         requests that this session be assigned the device-name of the
         printer that is paired with the terminal named in the request.
         If the device-type does not represent a printer, or if the
         device-name is not that of a terminal, then the server should
         deny the request.  It is anticipated that the device-name
         specified in this request would be one returned by the server
         when accepting a previous terminal session request (see the IS
         command below).  Since no means of authentication has been
         provided for, it is possible that the printer paired with the
         terminal specified in the ASSOCIATE command has already been
         assigned to some other Telnet session; in this case, the server
         should deny the request.

      7.1.4 Device Selection Rules

         To summarize, assume a TN3270E server has the following device
         pools defined to it (device-names that begin with a "T" are
         terminal devices; those that begin with a "P" are printers):

          Generic Terminal Pool              Specific Terminal Pool
          ---------------------              ----------------------
          TG000001 <--> PTG00001             TS000001 <--> PTS00001
          TG000002 <--> PTG00002             TS000002 <--> PTS00002
          TG000003 <--> PTG00003             TS000003 <--> PTS00003

          Generic Printer Pool               Specific Printer Pool
          --------------------               ----------------------
               PG000001                            PS000001
               PG000002                            PS000002
               PG000003                            PS000003

         Note that the only pool that absolutely must be defined to the
         server is the generic terminal pool.  The absence of other
         pools (or of partner printers for a terminal pool) simply means
         that the server is unable to satisfy as wide a variety of
         requests as would be possible if all pools were defined to it.

         Given the above configuration, the following rules apply:




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         - a generic terminal request can only be satisfied from the
           generic terminal pool (device-names TG000001 - TG000003).

         - a specific terminal request (allowable only via the CONNECT
           command) can be satisfied from either the generic or the
           specific terminal pool, although it is anticipated that the