GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc1921

Network Working Group J. Dujonc Request for Comments: 1921 Bull S.A. Category: Informational March 1996

                           TNVIP Protocol

Status of this Memo

 This memo provides information for the Internet community.  This memo
 does not specify an Internet standard of any kind.  Distribution of
 this memo is unlimited.

Abstract

 The goal of this document specifies a Telnet profile to support VIP
 terminal emulation allowing the access to the BULL hosts applications
 through a TCP/IP network.

Table of Contents

  1.       Motivation . . . . . . . . . . . . . . . . . . . . . . 2
  2.       Background . . . . . . . . . . . . . . . . . . . . . . 3
  3.       Telnet Options and Commands Used . . . . . . . . . . . 3
  3.1.      Terminal type option  . . . . . . . . . . . . . . . . 4
  3.1.1.      Subnegotiation of the Terminal Type . . . . . . . . 4
  3.1.2.      Terminal-types supported by the TNVIP protocol  . . 4
  3.1.3.      TNVIP terminal models . . . . . . . . . . . . . . . 5
  3.1.4.      Mailbox name  . . . . . . . . . . . . . . . . . . . 5
  3.2.      End of Record Option  . . . . . . . . . . . . . . . . 6
  3.3.      Binary Transmission option  . . . . . . . . . . . . . 6
  3.4.      Suppress Go Ahead option  . . . . . . . . . . . . . . 7
  4.       TNVIP functions  . . . . . . . . . . . . . . . . . . . 8
  4.1.      TNVIP terminal station  . . . . . . . . . . . . . . . 9
  4.1.1.      Local and online states . . . . . . . . . . . . . . 9
  4.1.2.      Data receiving  . . . . . . . . . . . . . . . . .  10
  4.1.3.      Data sending  . . . . . . . . . . . . . . . . . .  10
  4.2.      TNVIP Server functions  . . . . . . . . . . . . . .  10
  4.2.1.      VIP Terminal Manager  . . . . . . . . . . . . . .  10
  5.       TNVIP Messages Format  . . . . . . . . . . . . . . .  12
  5.1.      Address Field . . . . . . . . . . . . . . . . . . .  12
  5.2.      Command field . . . . . . . . . . . . . . . . . . .  13
  5.3.      Parameter field . . . . . . . . . . . . . . . . . .  14
  6.       The screen flow  . . . . . . . . . . . . . . . . . .  14
  6.1.      Screen data messages  . . . . . . . . . . . . . . .  14
  6.2.      Local state monitoring messages . . . . . . . . . .  15
  6.3.      Screen response messages  . . . . . . . . . . . . .  16
  6.3.1      Page overflow processing . . . . . . . . . . . . .  17

Dujonc Informational [Page 1] RFC 1921 TNVIP Protocol March 1996

  6.4.      Screen data purge indication message  . . . . . . .  17
  7.       The printer flow . . . . . . . . . . . . . . . . . .  17
  7.1.      Printer data messages . . . . . . . . . . . . . . .  17
  7.2.      Printer response messages . . . . . . . . . . . . .  18
  7.3.      7800 printer status management  . . . . . . . . . .  19
  7.4.      Printer state request message   . . . . . . . . . .  20
  7.5.      Printer state response messages . . . . . . . . . .  20
  7.6.      Printer purge indication message  . . . . . . . . .  20
  8.       The Screen Copy Printing flow  . . . . . . . . . . .  21
  8.1.      Screen copy request messages  . . . . . . . . . . .  21
  8.2.      Screen copy data message  . . . . . . . . . . . . .  21
  8.3.      Screen copy response messages . . . . . . . . . . .  22
  8.4.      Screen copy purge indication message  . . . . . . .  23
  9.       The TM attention . . . . . . . . . . . . . . . . . .  23
  10.      The Break Key  . . . . . . . . . . . . . . . . . . .  24
  11.      The Logout Key . . . . . . . . . . . . . . . . . . .  24
  12.      TNVIP messages list  . . . . . . . . . . . . . . . .  24
  12.1.     Screen Flow . . . . . . . . . . . . . . . . . . . .  24
  12.2.     Printer flow  . . . . . . . . . . . . . . . . . . .  26
  12.3.     Screen Copy Printing messages flow  . . . . . . . .  28
  13.      Security Considerations  . . . . . . . . . . . . . .  29
  14.      References . . . . . . . . . . . . . . . . . . . . .  30
  15.      Author's Address . . . . . . . . . . . . . . . . . .  30

1. Motivation

 P200 [7] and 7800 [8] VIP (Visual Information Projection) terminals
 differ mainly from NVT terminals [1] in that they work in block mode
 and have the capability to manage an associated printer. Generally in
 a DSA (Distributed Systems Architecture) network they are managed
 through the VIP transmission line procedure (character oriented).
 That is the reason why they are generically referred as VIP
 terminals.
 This document specifies the options to be modified successfully, to
 pass from the NVT terminal emulation supported on a Telnet
 connection, to a VIP terminal emulation. It defines also the format
 of the messages exchanged between the server and the client when the
 TNVIP protocol is successfully negotiated.

Dujonc Informational [Page 2] RFC 1921 TNVIP Protocol March 1996

2. Background

 VIP terminal family includes a broad range of different terminal
 types. They work in block mode with an ASCII or 8 binary bits set of
 characters.
 The Bull terminals in the DSA network environment use the services of
 a Terminal Manager (TM) [2]. It is generally installed in a
 communication processor (as a Datanet or Mainway system) where it
 assures the connection with the BULL host application generally
 through a DSA session.
 The Terminal Manager is in charge to present the terminal station and
 to manage the session connection to the host computer. It offers
 generally a possibility of dialog with the terminal to allow the user
 to modify the connection parameters, to manage the session
 (connection request, abort, etc ..). The set of commands and
 responses used is called "TM Local Dialog".

3. Telnet Options and Commands Used

 The mandatory telnet parameters to be negotiated successfully between
 the "TNVIP server" and the "TNVIP client" are :
  1. the Terminal-Type option [3] to define a VIP terminal model and

if necessary a Mailbox name to request a specific access point in

    the "TNVIP server",
  1. the End Of Record option [4] to delimit the TNVIP message at the

Telnet level. As the End Of Record (EOR) code indicates the end of

    an effective data unit, Telnet should attempt to send the data up
    to and including the EOR code together to promote communication
    efficiency.
  Others Telnet parameters, can be optionally negotiated as :
  1. the Binary Transmission option [5], when the terminal emulation

uses a 8 binary bits set of characters,

  1. the Suppress Go Ahead option [6], when no synchronisation of the

data transmission from the "TNVIP client" with the DSA session

    turn or the ISO session token is needed.
 When the two parties (the "TNVIP server" and the "TNVIP client") have
 negotiated successfully a TNVIP terminal type and the EOR telnet
 option, that means they agree to respect the TNVIP protocol (the
 TNVIP message format and the exchange rules).

Dujonc Informational [Page 3] RFC 1921 TNVIP Protocol March 1996

3.1 Terminal type option

 IAC DO TERMINAL-TYPE
    Sender (the "TNVIP server" party) is willing to receive terminal
    type information in a subsequent sub-negotiation.
 IAC WILL TERMINAL-TYPE
    Sender (the terminal "TNVIP client" party) is willing to send
    terminal-type information in a subsequent sub-negotiation.

3.1.1 Subnegotiation of the Terminal Type

 IAC SB TERMINAL-TYPE SEND IAC SE
    Sender (the "TNVIP server" party) requests the receiver to
    transmit his next terminal-type, and switch emulation modes (if
    more than one terminal type is supported).
 IAC SB TERMINAL-TYPE IS tnvip-terminal-model@MB-name IAC SE
    Sender (the terminal "TNVIP client" party) is stating the name of
    his current (or only) terminal-type. Optionally, a mailbox name
    can be added to request a particular access point in the "TNVIP
    server". By default, the "TNVIP server" uses a generic access
    point.

3.1.2 Terminal-types supported by the TNVIP protocol

 The TNVIP terminal type string given at the Telnet negotiation is
 formatted as follows :
    <TNVIP-terminal-model> [ <@ character> <Mailbox-name> ]
 The @ character is used as separator between the VIP-terminal-model
 and the Mailbox-name.

Dujonc Informational [Page 4] RFC 1921 TNVIP Protocol March 1996

3.1.3 TNVIP terminal models

 The valid TNVIP terminal models are the following ASCII character
 strings. (The table gives for each terminal model string the
 hexadecimal number indicating the associated DSA model number defined
 in the DSA terminal presentation protocols ).
               P200 family                      7800 family
  -------------------------------- --------------------------------
  !   TNVIP model  !    DSA code ! !   TNVIP model  !    DSA code !
  -------------------------------- --------------------------------
  !   VIP7700      !       33    ! !   VIP7804      !       3E    !
  !   VIP7760      !       3A    ! !   VIP7804V     !       4A    !
  !   DKU7005      !       3D    ! !   VIP7814      !       47    !
  !   DKU7007D     !       40    ! !   HDS7         !       4D    !
  !   DKU7105      !       41    ! !   VIP8800      !       4F    !
  !   DKU7107D     !       42    ! --------------------------------
  !   DKU7211      !       45    !
  !   DKU7211D     !       4E    !
  --------------------------------
 The D character at the end of the string indicates that the terminal
 supports the Remote Forms function [9]. It is the capability to store
 forms in the terminal allowing the host application to display a form
 stored in the terminal sending a short length command without sending
 all the data of the form. This function is usually supported by the
 terminal concentrators.

3.1.4 Mailbox name

 The mailbox name allows the "TNVIP client" to request a specialized
 access point referenced by this name in the "TNVIP server". It is an
 ASCII character string. Its presence in the Telnet terminal type
 string is optional. When not present, a generic (default) access can
 be provided by the "TNVIP server".
 When the "TNVIP server" is a gateway to DSA hosts, the mailbox name
 defines the DSA session access point of the terminal in the server.
 Its length is limited to 12 characters. Lower case characters are
 allowed but are processed as upper case. This string is generally
 used to identify a specific terminal station (having a printer for
 example) or to use a particular declaration of this terminal in the
 "TNVIP server".

Dujonc Informational [Page 5] RFC 1921 TNVIP Protocol March 1996

3.2 End of Record Option

 VIP device communications are block oriented. That is, each partner
 buffers data until an entire "message" has been built, at which point
 the data are sent to the other side. The end of a message is
 understood to be the last byte transmitted. The Telnet EOR command is
 used to delimit these natural blocks of TNVIP data within the Telnet
 data stream. An <EOR> is sent at the end of each TNVIP message, in
 both directions.
 IAC WILL END-OF-RECORD
    The sender of this command requests permission to begin
    transmission of the Telnet END-OF-RECORD (EOR) code when
    transmitting data characters, or the sender of this command
    confirms it will now begin transmission of EORs with transmitted
    data characters.
 IAC DO END-OF-RECORD
    The sender of this command requests that the sender of data starts
    transmitting the EOR code when transmitting data, or the sender of
    this command confirms that the sender of data is expected to
    transmit EORs.

3.3 Binary Transmission option

 According to the character set used by the emulation, the "TNVIP
 client" and the "TNVIP server" can be led to negotiate the Telnet
 binary transmission option.
 If either side wishes to transmit the decimal value 255 and have it
 interpreted as data, it must "double" this byte. In other words, a
 single occurrence of decimal 255 will be interpreted by the other
 side as an IAC, while two successive bytes containing decimal 255
 will be treated as one data byte with a value of decimal 255.
 IAC DO TRANSMIT-BINARY
    Sender requests that sender of the data starts transmitting or
    confirms that the sender of data is expected to transmit
    characters that are to be interpreted as 8 bits of binary data by
    the receiver.
 IAC WILL TRANSMIT-BINARY
    Sender requests permission to begin transmitting, or confirms it
    will now begin transmitting binary data.

Dujonc Informational [Page 6] RFC 1921 TNVIP Protocol March 1996

 IAC WON'T TRANSMIT-BINARY
    If the connection is already being operated in binary transmission
    mode, the sender of this command demands to begin transmitting
    data characters which are to be interpreted as standard NVT ASCII
    characters by the receiver of the data. If the connection is not
    already being operated in binary transmission mode, the sender of
    this command refuses to begin transmitting characters which are to
    be interpreted as binary characters by the receiver of the data
    (i.e., the sender of the data requests to continue transmitting
    characters in its present mode).
 IAC DON'T TRANSMIT-BINARY
    If the connection is already being operated in binary transmission
    mode, the sender of this command requests that the sender of the
    data start transmitting characters which are to be interpreted as
    standard NVT ASCII characters by the receiver of the data
    (i.e.,the party sending this command). If the connection is not
    already being operated in binary transmission mode, the sender of
    this command requests that the sender of data continue
    transmitting characters which are to be interpreted in the present
    mode.

3.4 Suppress Go Ahead option

 The "TNVIP client" can use the receiving of the Telnet GoAhead
 command as the signal allowing the terminal operator to transmit
 data. That can allow the synchronisation between the data transmitted
 from the terminal and the DSA "turn".
 When the Suppress Go Ahead option is not negotiated, the "TNVIP
 server" must send the Telnet Go Ahead command (GA) when its input
 message queue (from the "TNVIP client") is empty and the DSA turn is
 at the terminal side, to invite the terminal to transmit some data.
 To suppress this mechanism, the "TNVIP client" can request the no
 sending of the Telnet GoAhead commands by the "TNVIP server",
 negotiating the Suppress GO Ahead option of the Telnet Protocol.
 In this case, the terminal transmission to the "TNVIP server" is
 synchronised on the transport credit.
 Note: The Telnet GA command never need to be sent by the "TNVIP
       client" even if the telnet Suppress Go Ahead has not been
       negotiated.

Dujonc Informational [Page 7] RFC 1921 TNVIP Protocol March 1996

 IAC DO SUPPRESS-GO-AHEAD
 The sender of this command (the "TNVIP client" party) requests that
 the sender of data starts suppressing GA when transmitting data.
 IAC WILL SUPPRESS-GO-AHEAD
    The sender of this command (the "TNVIP server" party) confirms it
    will now begin suppressing transmission of GAs with transmitted
    data characters.
 IAC DON'T SUPPRESSS-GO-AHEAD
    The sender of this command (the "TNVIP client" party) requests
    that the receiver of the command start transmitting GAs when
    transmitting data.
 IAC WON'T SUPPRESS-GO-AHEAD
    The sender of this command (the "TNVIP server" party) confirms it
    will now begin transmitting the GA character when transmitting
    data characters.

4. TNVIP functions

 The TNVIP protocol allows the following functions :
  1. Support of a VIP terminal emulation addressing the screen and its

associated printer .

  1. Selection of the terminal type model at the connection time.
  1. Specific or generic access to the "TNVIP server" by referencing or

not a Mailbox name.

  1. TNVIP protocol independent of the terminal data presentation

protocol (7800 or P200).

  1. Support of the DSA End To End Acknowledgement.
  1. Support of the DSA Terminal Manager local attention.
  1. Support of the DSA turn to the terminal side.
  1. Support of the DSA secret read.
  1. Control of the hard copy.

Dujonc Informational [Page 8] RFC 1921 TNVIP Protocol March 1996

4.1 TNVIP terminal station

 The "TNVIP client" acts as the interface adapter between the TNVIP
 connection and an application program. The "TNVIP client" is mainly
 defined to support a VIP terminal emulation program but can be used
 by other else program using the TNVIP protocol.
 A VIP terminal emulation manages:
  1. a screen buffer,
  1. a printer buffer if it supports the associated printer,
  1. the interface with the communication line
 and runs using the following rules:
 When the VIP terminal emulation exchanges a message on the
 communication line, it is in the BUSY state until the end of the
 message exchange. That means when the VIP terminal is sending a
 message it can't receive and when it is receiving a message it can't
 send.
 Note: If a VIP terminal works in the half duplex mode, as the TNVIP
       protocol uses a Telnet connection it allows a full duplex
       mode processing.

4.1.1 Local and online states

 The VIP terminal has the capability to switch between these two
 states. The LOCAL state is generally used to process local terminal
 tests or to modify the configuration. In this state, the data coming
 from the line are ignored.
 The LOCAL state allows the "TNVIP client" to request to the server
 the screen and printer data flows to be suspended.
 The ONLINE state indication allows the "TNVIP server" to resume the
 screen and printer flows.
 For these reasons the TNVIP protocol differentiates the screen and
 printer flows from the screen copy printing flow and defines to
 report the two states to the "TNVIP server".

Dujonc Informational [Page 9] RFC 1921 TNVIP Protocol March 1996

4.1.2 Data receiving

 When a VIP terminal emulation receives a data message from the line,
 according to the address given in the header message,it sends data to
 the screen buffer or to the printer buffer.
 A message received at the screen or printer address is deleted and
 ignored if the terminal emulation is in the LOCAL state and a BUSY
 status is returned.
 The printer buffer is busy when the terminal is transmitting the data
 from the printer buffer to the printer device. A data message for the
 printer is deleted and ignored if the terminal is in the printing
 state and a BUSY status is returned.
 When a BUSY state is encountered, the "TNVIP client" according to the
 type of message received (request or indication) reports or not the
 BUSY acknowledgement to the "TNVIP server".

4.1.3 Data sending

 A VIP terminal emulation can send message even if the terminal is in
 the LOCAL state.

4.2 TNVIP Server functions

4.2.1 VIP Terminal Manager

 Its function is to act as a gateway between the VIP terminal and the
 VIP application. Generally the application is a remote DSA
 application.
 It manages the screen and printer devices of the VIP terminal
 station.

Dujonc Informational [Page 10] RFC 1921 TNVIP Protocol March 1996

 In the following example figure, the "TNVIP server" is a DSA server
 and manages three VIP terminal units TU1, TU2 and TU3.
  Generic access
  --------------
            !----> LD 1S ----> DV 1S (screen)  ---->!
  MB 1 --> SN 1                                     TU 1
            !----> LD 1P ----> DV 1P (printer) ---->!
  Specific accesses
  -----------------
            !----> LD 2S ----> DV 2S (screen)  ---->TU 2
  MB 2 --> SN 2
            !----> LD 2P ----> !
                               !
            !----> LD 3P ----> DV 3S (printer) ---->!
  MB 3 --> SN 3                                     TU 3
            !----> LD 3S ----> DV 3P (screen)  ---->!
 Each Terminal Unit (TU object) is declared as containing one or two
 devices (DV objects). The Terminal Manager maps this physical
 representation to a logical representation where the station (SN
 object) is the logical representation of a terminal unit, and the
 logical device (LD) object a logical representation of the real
 device.
  1. TU1 will be chosen by default on generic request (without mailbox

name) or by the MB1 name addressing on specific request. It can

    manage the associated printer device.
  1. MB2 will be addressed to access the TU2 terminal unit. TU2 is

defined in a specific way because it will be presented to the host

    application as a station composed of a screen (the TU2 one's) and
    a printer (the TU3 one's).
  1. MB3 will be addressed to access TU3 terminal unit. TU3 is also

defined in a specific way because the printer device is shared by

    several logical stations (SN2 and SN3) and must be well
    identified.

Dujonc Informational [Page 11] RFC 1921 TNVIP Protocol March 1996

5. TNVIP Messages Format

 Each TNVIP message is delimited by the Telnet EOR command.
 Therefore, a TNVIP message has the following format:
  <TNVIP Header> <parameters> <IAC EOR>
 The TNVIP header is mandatory and have a fixed length of two bytes.
 Some TNVIP messages need no parameter. In this case, the TNVIP
 message has the following construction:
  <TNVIP Header> <IAC EOR>
 It is strongly recommended that Telnet commands (other than IAC IAC)
 should be sent between TNVIP messages, with no TNVIP header and no
 trailing IAC EOR. If a TNVIP data message containing any other IAC-
 command sequence (other than IAC IAC) is received, it is
 implementation dependent when the IAC-command sequence will be
 processed, but it must be processed. The receiver may process it
 immediately, which in effect causes it to be processed as if it had
 been received before the current TNVIP message, or the processing may
 be deferred until after the current TNVIP message has been processed.
 It is because of this ambiguity that the presence of Telnet commands
 within a TNVIP message is not recommended; neither "TNVIP client"s
 nor "TNVIP server"s should send such data.
 The TNVIP header contains 2 bytes. The first one indicates the
 address <ADR> and the second the command <CDE>.

5.1 Address Field

 The <ADR> address field is mandatory and is defined on one byte.
 The TNVIP protocol defines 3 addresses:
  1. ADR = SCREEN = 96 (0x60) for the screen commands flow,
  1. ADR = PRINTER = 104 (0x68) for the printer commands flow,
  1. ADR = SCPM = 105 (0x69) for the screen copy printing commands

flow.

 A request message with an unknown or unsupported address will be
 discarded by the receiver which replies with a NOT-AVAILABLE response
 message.

Dujonc Informational [Page 12] RFC 1921 TNVIP Protocol March 1996

5.2 Command field

 The <CDE> command field is mandatory and defined on one byte.
 The command byte <CDE> is structured as follows:
  <Command-Type><Message-Type>
  1. The Command-Type fills the six most significant bits of the <CDE>

byte. The most significant bit is always 0.

    Its value is ranged from 0 to 31 included. It defines the command
    associated to the message for the flow identified by the address
    field.
  1. The Message-Type fills the two less significant bits of the <CDE>

byte.

    0 = Indication message. No response message is expected. An
    indication message with an undefined command type or with an
    unknown address is deleted and ignored.
    1 = Request message. The sender of a request message is waiting
    for a response message having the same address value. When a
    request message is sent for a given address, it is not allowed to
    send another request to the same address before the receiving
    response. If an end point receives a request before having sent
    the response of the previous request, it deletes the second
    request but have to send back a PROTOCOL-VIOLATION response after
    the response of the first request. A request message with a not
    defined address is replied to by a NOT-AVAILABLE response message.
    A request message with an unknown or unsupported command <CDE> for
    this address will be deleted by the receiver and replied to by an
    UNKNOWN-COMMAND response message.
    2 = Response message. This message is the response to the current
    request message. The receiver of this message is allowed to send
    another request message on the flow defined by the ADR field.
    3 = Response and request message. This message is a positive
    response to the current request message sent by the receiver, but
    is also a request message.

Dujonc Informational [Page 13] RFC 1921 TNVIP Protocol March 1996

 The following table gives the <CDE> commands list with their
 hexadecimal values
  Command          Indication  Request  Response  Resp/Req
  --------------------------------------------------------
  DATA                00         01
  PASSW               04         05
  ACK                                      0A
  ERROR                                    0E
  BUSY                                     12
  ABORTED                                  16
  PURGED                                   1A
  NOT-AVAILABLE                            1E
  PROTOCOL-VIOLATION                       22
  UNKNOWN-COMMAND                          26
  PURGE               28
  LOCAL-STATE                    2D
  ONLINE-STATE        30
  STATE-REQ                      35
  READY                                    3A
  STANDBY                                  3E
  COPY-REQ                       41
  LOCAL-COPY                                         47

5.3 Parameter field

 This field has a variable length and its content is depending on the
 two previous fields (address and command).

6. The screen flow

 All the following messages contain the value SCREEN = 96 (0x60) in
 the ADR field.

6.1 Screen data messages

 These messages are defined to transport in the parameter field of the
 TNVIP message, the data in the terminal presentation negotiated by
 the "Terminal Type" telnet command.
 The parameter has the following format:
  <FC1> <FC2> <STX> < screen data>
  1. The FC1, FC2 bytes are the functions codes of the VIP procedure

transmission [9]. Their values are comprised between 32 (0x20)

    included and 127 (0x7F) included.

Dujonc Informational [Page 14] RFC 1921 TNVIP Protocol March 1996

  1. The STX byte is defined by the value 2 and acts as the introducer

of the screen data.

 A screen data message can be sent in a request or in an indication
 message. The command values are defined as follows:
  <CDE> = DATA indication = 0
  <CDE> = DATA request = 1
  <CDE> = PASSWORD indication = 4
  <CDE> = PASSWORD request = 5
 Generally, the "TNVIP server" only sends indication messages to the
 screen. The request message is used mainly for the printer device.
 But a DSA/TNVIP gateway server should use the screen data request
 message when it processes a DSA end to end acknowledgement request
 from the DSA application and synchronizes the response message
 receipt with the DSA end to end acknowledgement.
 The password request and the password indication message are defined,
 to be used by the programs in the "TNVIP client" machine which don't
 emulate terminal. In this way, they have the indication that a secret
 read (password acquisition) is requested by the "TNVIP server". When
 the program is a terminal emulation this information is not necessary
 because the data contains the terminal presentation command to
 request this secret read.

6.2 Local state monitoring messages

 Before to switch in the local state, the "TNVIP client" sends a
 LOCAL-STATE request message to the "TNVIP server". This last one
 sends back an acknowledgement message and suspends the screen and
 printer data flow until it receives a LINE-STATE indication message.
 Note: In the local state, only the messages from the "TNVIP server"
       to the screen or printer devices are deleted. The messages
       from the "TNVIP client" screen device or the messages
       associated to others addresses are allowed.
 The following command values are defined as:
  <CDE> = LOCAL-STATE request = 45 (0x2D). It is sent by the "TNVIP
  client". There is no parameter field.

Dujonc Informational [Page 15] RFC 1921 TNVIP Protocol March 1996

  <CDE> = ONLINE-STATE indication = 48 (0x30). It is sent by the
  "TNVIP client" to indicate the "TNVIP server" is allowed to resume
  the screen data flow. There is no parameter field.

6.3 Screen response messages

 These messages are indications used to respond to the screen data
 request previously received.
 The command values are defined as follows:
  <CDE> = ACK response indication = 10 (0x0A). The screen data
  previously received has been well processed or the LOCAL STATE is
  acknowledged by the "TNVIP server". There is no parameter field.
  <CDE> = ERR response indication = 14 (0x0E). The screen data
  previously received has not been correctly processed. There is no
  parameter field.
  <CDE> = BUSY response indication = 18 (0x12). The screen data
  previously received has been deleted because the terminal is in the
  local state. There is no parameter field.
  <CDE> = ABORTED response indication = 22 (0x16). The receipt of the
  screen data request has been aborted by a reset terminal command.
  There is no parameter field.
  <CDE> = PURGED response indication = 26 (0x1A). The processing of
  the screen data request has been aborted by a purge indication
  message. There is no parameter field.
  <CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The screen
  device is not supported. Normally this command has never to be
  generated because the screen device should always be present. There
  is no parameter field.
  <CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
  screen request received has been deleted because an other screen
  request is already in process. That means several screen request
  messages have been sent without waiting for the response. It is a
  consequence of the non-compliance of the protocol. There is no
  parameter field.
  <CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The screen
  request received has been deleted because the <CDE> field value is
  unknown. It is a consequence of the non-compliance of the protocol.
  There is no parameter field.

Dujonc Informational [Page 16] RFC 1921 TNVIP Protocol March 1996

6.3.1 Page overflow processing

 The page overflow processing is not supported through the TNVIP
 protocol to avoid the retransmission of the message. That leads the
 "TNVIP client" side to process it locally. When a data message
 induces a page overflow, the terminal emulation alerts the user
 possibly requesting (in manual mode) an "enter" action before
 clearing the screen and reprocessing the data received.
 Note: When the "TNVIP client" is processing a page overflow , the
       terminal emulation should be in the BUSY state and should
       stop getting message from the line ("TNVIP server") until the
       page overflow processing is complete.

6.4 Screen data purge indication message

 This message is used to purge the current screen request message.
 When the side which receive the message has not already acknowledged
 the screen request, it tries to abort the processing of the request
 and returns a screen purged response message. If it has already
 replied, it ignores and deletes the message.
 The following command value is defined as:
  <CDE> = PURGE indication = 40 (0x28). There is no parameter field.

7. The printer flow

 All the following messages contain the PRINTER value 104 (0x68) in
 the ADR field. The support of this address is optional. If the "TNVIP
 server" doesn't address this device, no message with this address
 will be exchanged. If the "TNVIP client" receives a request message
 with this address and does not support the printer, it replies with a
 printer NOT-AVAILABLE response message.

7.1 Printer data messages

 These messages are defined to transport the printer data in the
 parameter field of the TNVIP message. These messages are only sent
 from the "TNVIP server" to the "TNVIP client".
 The parameter has the following format:
  <FC1> <FC2> <STX> <printer data>
  1. The FC1, FC2 bytes are the function codes of the VIP procedure

transmission. Their values are ranged from 32 (0x20) to 127

    (0x7F) included.

Dujonc Informational [Page 17] RFC 1921 TNVIP Protocol March 1996

  1. The STX byte is defined by the value 2 and acts as the introducer

of the printer data.

 To manage correctly the printer device, the protocol only defines
 request message. Whereas the "TNVIP server" is ensured than the
 "TNVIP client" processes a screen data message only when the previous
 one have been processed. When it receives a printer data message, the
 "TNVIP client" transfers it in the printer buffer. The terminal is
 busy only during this transfer. So, if the "TNVIP client" receives
 another printer data it deletes them because the previous printing
 (transfer between the printer buffer and the printer) is not ended.
 The printer data structure depends on the terminal presentation
 family (P200 or 7800). The two presentations define two modes of
 printing. The first one needs the printer data are in the
 presentation of the screen (7800 or P200 commands) and data are
 converted by the terminal in the printer presentation (TTY, SDP,
 copy. The second mode allows to give the printer data in the real
 presentation of the printer. For this reason it is called
 "transparent print".
 In the P200 terminal presentation, transparent print data are
 introduced by the sequence of the two ASCII characters ESC Z (0x1B
 0x5A ). P200 formatted print are introduced by the sequence of two
 ASCII characters ESC X (0x1B 0x58) or ESC Y (0x1B 0x59).
 In the 7800 terminal presentation, transparent print data are
 introduced by the command PTD (Print Transparent Data). 7800
 formatted print are introduced by the command PHD (Print Host Data).
  <CDE> = DATA request = 1 (0x01).

7.2 Printer response messages

 These messages are used to report the printing end status of the
 printer data request previously received.
 The following command values are defined as:
  <CDE> = ACK response indication = 10 (0x0A). The printer data
  previously received have been well processed.
  <CDE> = ERR response indication = 14 (0x0E). The printer data
  previously received have not been correctly processed (invalid
  command, buffer overflow , printer off...)
  <CDE> = BUSY response indication = 18 (0x12). The printer data
  received have been deleted because the previous printing request is

Dujonc Informational [Page 18] RFC 1921 TNVIP Protocol March 1996

  not ended. Several printer data request messages have been sent
  without waiting for the response.
  <CDE> = ABORTED  response indication = 22 (0x14). The printing has
  been aborted by the terminal operator.
  <CDE> = PURGED response indication = 26 (0x18). The printing request
  has been aborted by a printer data purge indication message.
  <CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The printer
  device is not supported.
  <CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
  printer request received has been deleted because an other printer
  request is already in process. That means several printer request
  messages have been sent without waiting for the response. It is a
  consequence of the non-compliance of the protocol. There is no
  parameter field.
  <CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The
  printer request received has been deleted because of an unknown
  <CDE> field value. It is a consequence of the non-compliance of the
  protocol. There is no parameter field.
  For all the above commands, the parameter field may contain
  specific terminal status if one was requested in the printer data
  received (response to PDENQ 7800 terminal presentation command).

7.3 7800 printer status management

 When emulating a 7800 terminal [8], the "TNVIP client" takes charge
 of adding to the printer data the printer differed status request
 (PDENQ 7800 command) to synchronize the printing end with the sending
 of the printer acknowledgement response.
 Some DSA applications are written to manage the 7800 printer status,
 so they send themselves the printer status request at the beginning
 of the printer data. That is the reason why when the "TNVIP client"
 receives this command at the beginning of the printer data, it must
 send back the 7800 status response in the parameter field of the
 printer data response message.
 The 7800 terminal presentation defines also immediate printer status
 request and response (PENQ which allows to get an immediate response
 indicating the current printer status). These commands have to be
 exchanged in the TNVIP screen data flow.

Dujonc Informational [Page 19] RFC 1921 TNVIP Protocol March 1996

7.4 Printer state request message

 This message is sent by the "TNVIP server" to know the printer state
 of the "TNVIP client" without sending printer data.
 The following command value is defined as:
  <CDE> = STATE-REQ request = 53 (0x35). There is no parameter field.

7.5 Printer state response messages

 These messages are sent by the "TNVIP client" in order to report the
 printer state to the "TNVIP server".
 The following command values are defined as:
  <CDE> = READY response indication = 58 (0x3A). The printer state is
  ready to print. There is no parameter field.
  <CDE> = STANDBY response indication = 62 (0x3E). The printer device
  is in standby and is temporarily unavailable. There is no parameter
  field.
  <CDE> = PURGED response indication = 26 (0x1A). The printer state
  request has been aborted by a printer state purge indication
  message. There is no parameter field.
  <CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The printer
  device is not supported. There is no parameter field.
  <CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
  printer state request received has been deleted because an other
  printer request is already in process. That means several printer
  request messages have been sent without waiting for the response. It
  is a consequence of the non-compliance of the protocol. There is no
  parameter field.
  <CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The printer
  state request received has been deleted because the <CDE> field
  value is unknown. It is a consequence of the non-compliance of the
  protocol. There is no parameter field.

7.6 Printer purge indication message

 This message is used by the "TNVIP server" to purge the current
 printer request message. When the "TNVIP client" receives this
 message, if it has not already acknowledged the printer data, it
 aborts the printing and returns a printer data purge acknowledgement

Dujonc Informational [Page 20] RFC 1921 TNVIP Protocol March 1996

 response message. If it has already replied, it ignores and deletes
 the message.
 The printer purge command value is defined as:
  <CDE> = PURGE indication = 40 (0x28). There is no parameter field.

8. The Screen Copy Printing flow

 All the following messages contain the SCPM address value 105 (0x69)
 in the ADR field. The support of this address is mandatory.

8.1 Screen copy request messages

 As the printer device can be used by the "TNVIP server", if the
 terminal user wishes a screen copy printing, the "TNVIP" client has
 to synchronize the user request with the "TNVIP server" printing .
 The TNVIP protocol defines that the "TNVIP client" has to inform the
 "TNVIP server" when it wants to print a screen copy and waits for its
 authorization before beginning
 The following command values are defined as:
  <CDE> = COPY-REQ request = 65 (0x41). It is used from the "TNVIP
  client" to the "TNVIP server" to request a screen copy printing.
  <CDE> = LOCAL-COPY response and request = 71 (0x47). It is sent by
  the "TNVIP server" to acknowledge the COPY-REQ message indicating
  the screen copy can be done locally. It is also a request message
  because it is equivalent to a screen copy data request message and
  the "TNVIP server" is waiting for a screen copy response message
  from the "TNVIP client" but on the SCPM flow. There is no parameter
  field.

8.2 Screen copy data message

 They are defined in order to transport in the parameter of the
 message the screen copy data in the terminal presentation. It is used
 by the "TNVIP client" when it wants to send the screen copy data
 directly to the DSA application (a VIP terminal using a VIP
 transmission procedure indicates this special request by the STA byte
 =PRT=0x1A).

Dujonc Informational [Page 21] RFC 1921 TNVIP Protocol March 1996

 The parameter field has the following format:
  <FC1> <FC2> <STX> <screen-copy-data>
  1. The FC1, FC2 bytes are the functions codes of the VIP procedure

transmission. Their values are ranged from 32 (0x20) to 127

    (0x7F) included.
  1. The STX byte is defined by the value 2 and acts as the introducer

of the screen data.

 Screen copy data message can be sent in a request or indication
 message.
 The command values are defined as follows:
  <CDE> = DATA indication = 0
  <CDE> = DATA request = 1

8.3 Screen copy response messages

 These messages are sent by the "TNVIP client" (local copy) to report
 the end of printing status of the screen copy.
 The ACK response is also used by the "TNVIP server" to acknowledge a
 screen copy data request sent to the host application.
 The ERR message is also used by the server to refuse a COPY-REQ
 message.
 The following command values are defined as:
  <CDE> = ACK response indication = 10 (0x0A). The "TNVIP client"
  reports the screen copy has been well printed or the "TNVIP server"
  acknowledges the screen copy data request. There is no parameter
  field.
  <CDE> = ERR response indication = 14 (0x0E). The screen copy has not
  been correctly printed (invalid command, buffer overflow ...) or has
  been refused by the "TNVIP server". It can optionally contain a
  reason code value defined on one byte.
  1. 1 : The printer is busy, retry later.
  <CDE> = BUSY response indication = 18 (0x12). The screen copy has
  not been correctly printed because the printer device is already
  printing. There is no parameter field.

Dujonc Informational [Page 22] RFC 1921 TNVIP Protocol March 1996

  <CDE> = ABORTED  response indication =22 (0x16). The screen copy has
  been aborted by the terminal operator. There is no parameter field.
  <CDE> = PURGED response indication = 26 (0x1A). The screen copy
  request message has been aborted by a purge indication message.
  There is no parameter field.
  <CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The screen
  copy has not been correctly printed because the printer device is
  not supported. There is no parameter field.
  <CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
  screen copy request received has been deleted because an other
  screen copy request is already in process. That means several screen
  copy request messages have been sent without waiting for the
  response. It is a consequence of the non-compliance of the protocol.
  There is no parameter field.
  <CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The screen
  copy request received has been deleted because the <CDE> field value
  is unknown. It is a consequence of the non-compliance of the
  protocol. There is no parameter field.

8.4 Screen copy purge indication message

 This message is used to purge the current screen copy request
 message. When the "TNVIP server" or the "TNVIP client" receives this
 message, if it has not already acknowledged the request message, it
 returns a screen copy purge acknowledgement message. If it has
 already replied, it ignores and deletes the message.
 The following command value is defined as:
  <CDE> = PURGE indication = 40 (0x28).There is no parameter field.

9. The TM attention

 The TM attention is the signal used to activate the local dialog of
 the DSA Terminal Manager.
 The Telnet Abort Output (AO) command [1] is the mechanism used to
 implement the TM attention key support in TNVIP.
 IAC AO (0xFF 0xF5)
 In order to implement the TM attention key support, "TNVIP clients"
 should provide a key (or combination of keys) that is identified as
 mapping to the TM attention key. When the user presses this key(s),

Dujonc Informational [Page 23] RFC 1921 TNVIP Protocol March 1996

 the "TNVIP client" should transmit a Telnet AO command to the "TNVIP
 server".
 Upon receipt of the AO command, a "TNVIP server" that implements the
 DSA Terminal Manager should enter in what will be loosely termed "TM
 Local Dialog", suspending the eventual DSA host connection, else it
 should simply ignore it.

10. The Break Key

 Generally, there is no break key on the real VIP terminal. The break
 signal is transmitted to the host application through a TM local
 dialog command ($*$BRK for example)
 On "TNVIP client" emulating VIP terminal, it is often possible to map
 the break signal on a special key combination or by other way (using
 mouse ...).
 The Telnet Break (BRK) command [1] is used to map the Break signal of
 the TNVIP.
 IAC BRK (0xFF 0xF3)

11. The Logout Key

 The Telnet Interrupt Process (IP) command [1] can be used to map the
 logout command of the TM Local Dialog ($*$LO for example) if it is
 implemented on the "TNVIP server".
 IAC IP (0xFF 0xF4)

12. TNVIP messages list

 All the TNVIP commands are summarized here after (and the values are
 given in hexadecimal).

12.1 Screen Flow

 Data request (allowed in the two ways)
  SCREEN DATA-REQ <FC1> <FC2> STX [<screen-data>]  IAC EOR
  60     01       <FC1> <FC2> 02  [<screen-data>]  FF  EF
  1. Allowed responses to the screen Data request.
    SCREEN ACK  IAC EOR
    60     0A   FF  EF

Dujonc Informational [Page 24] RFC 1921 TNVIP Protocol March 1996

    SCREEN ERROR  IAC EOR
    60     0E     FF  EF
    SCREEN BUSY  IAC EOR
    60     12    FF  EF
    SCREEN ABORTED  IAC EOR
    60     16       FF  EF
    SCREEN PURGED  IAC EOR
    60     1A      FF  EF
 Password request (only from the "TNVIP server" to the "TNVIP client")
  SCREEN PASSW-REQ <FC1> <FC2> STX [<screen-data>]  IAC EOR
  60     05        <FC1> <FC2> 02  [<screen-data>]  FF  EF
  1. Allowed responses to the password request.
    SCREEN ACK  IAC EOR
    60     0A   FF  EF
    SCREEN ERROR  IAC EOR
    60     0E     FF  EF
    SCREEN BUSY  IAC EOR
    60     12    FF   EF
    SCREEN ABORTED  IAC EOR
    60     16       FF  EF
    SCREEN PURGED  IAC EOR
    60     1A      FF  EF
 Local state request (only from the "TNVIP client" to the "TNVIP
 server").
  SCREEN LOCAL-ST IAC EOR
  60     2D       FF  EF
  1. Allowed responses to the Local state request.
    SCREEN ACK  IAC EOR
    60     0A   FF  EF
    SCREEN PURGED  IAC EOR
    60 1A FF EF

Dujonc Informational [Page 25] RFC 1921 TNVIP Protocol March 1996

 Responses to request violating the TNVIP protocol (allowed in the two
 ways)
  SCREEN NOT-AVAIL  IAC EOR
  60     0E         FF  EF
  SCREEN PROT-VIOL  IAC EOR
  60     22         FF  EF
  SCREEN UNKN-CDE  IAC EOR
  60     26        FF  EF
 Indications (allowed in the two ways)
  SCREEN DATA-IND <FC1> <FC2> STX [<screen-data>]  IAC EOR
  60     00       <FC1> <FC2> 02  [<screen-data>]  FF  EF
  SCREEN PURGE  IAC EOR
  60     28     FF  EF
 Password indication (only from the "TNVIP server" to the "TNVIP
 client").
  SCREEN PASSW-IND <FC1> <FC2> STX [<screen-data>]  IAC EOR
  60     04        <FC1> <FC2> 02  [<screen-data>]  FF  EF
 On line state indication (only from the "TNVIP client" to the "TNVIP
 server").
  SCREEN ONLINE-ST  IAC EOR
  60     30         FF  EF

12.2 Printer flow

 Data request (only from the "TNVIP server" to the "TNVIP client")
  PRINTER DATA-REQ <FC1> <FC2> STX [<printer-data>]  IAC EOR
  68 01 <FC1> <FC2> 02 [<printer-data>] FF EF
  1. Allowed responses to the printer data request.
    PRINTER ACK [<status>]  IAC EOR
    68      0A  [<status>]  FF  EF
    PRINTER ERROR  [<status>] IAC EOR
    68      0E     [<status>] FF  EF

Dujonc Informational [Page 26] RFC 1921 TNVIP Protocol March 1996

    PRINTER BUSY [<status>]  IAC EOR
    68      12   [<status>]  FF  EF
    PRINTER ABORTED  [<status>] IAC EOR
    68      16       [<status>] FF  EF
    PRINTER PURGED  [<status>] IAC EOR
    68      1A      [<status>] FF  EF
    PRINTER NOT-AVAIL  [<status>] IAC EOR
    68      1E         [<status>] FF  EF
 State request (only from the "TNVIP server" to the "TNVIP client")
  PRINTER STATE-REQ  IAC EOR
  68      35         FF  EF
  1. Allowed responses to the state request.
    PRINTER READY  IAC EOR
    68      3A     FF  EF
    PRINTER STANDBY  IAC EOR
    68      3E       FF  EF
    PRINTER PURGED  IAC EOR
    68      1A      FF  EF
    PRINTER NOT-AVAIL  IAC EOR
    68      1E         FF  EF
 Responses to request violating the TNVIP protocol (allowed in the two
 ways)
  PRINTER PROT-VIOL  IAC EOR
  68      22         FF  EF
  PRINTER UNKN-CDE  IAC EOR
  68      26        FF  EF
 Indication (only from the "TNVIP server" to the "TNVIP client")
  PRINTER PURGE  IAC EOR
  68 28 FF EF

Dujonc Informational [Page 27] RFC 1921 TNVIP Protocol March 1996

12.3 Screen Copy Printing messages flow

 Copy request (only from the "TNVIP client" to the "TNVIP server")
  SCPM COPY-REQ  IAC EOR
  69   41        FF  EF
  1. Allowed responses to the copy request (from the "TNVIP server" to

the "TNVIP client")

    SCPM  ERROR  <reason> IAC EOR
    69    0E     <reason> FF  EF
    SCPM  PURGED  IAC EOR
    69    1A      FF  EF
    SCPM  NOT-AVAIL  IAC EOR
    69    1E         FF  EF
    SCPM  LOCAL-COPY-RQ   IAC EOR
    69    47              FF  EF
 Local copy request (only from the "TNVIP server" to the "TNVIP
 client" )
  SCPM  LOCAL-COPY-RQ   IAC EOR
  69    47              FF  EF
  1. Allowed responses to the local copy request (from the "TNVIP

client" to the "TNVIP server").

    SCPM ACK  IAC EOR
    69   0A   FF  EF
    SCPM ERROR  IAC EOR
    69   0E     FF  EF
    SCPM BUSY IAC EOR
    69   12   FF  EF
    SCPM ABORTED IAC EOR
    69   16      FF  EF
    SCPM PURGED IAC EOR
    69   1A     FF  EF
    SCPM NOT-AVAIL IAC EOR
    69   1E        FF  EF

Dujonc Informational [Page 28] RFC 1921 TNVIP Protocol March 1996

 Data request. (only from the "TNVIP client" to the "TNVIP server")
  SCPM DATA-REQ <FC1> <FC2> STX [<screen-data>]  IAC EOR
  69   01       <FC1> <FC2> 02  [<screen-data>]  FF  EF
  1. Allowed responses to the data request
    SCPM ACK  IAC EOR
    69   0A   FF  EF
    SCPM PURGED IAC EOR
    69   1A     FF  EF
    SCPM NOT-AVAIL IAC EOR
    69   1E        FF  EF
 Responses to request violating the TNVIP protocol (allowed in the two
 ways)
  SCPM PROT-VIOL  IAC EOR
  69   22         FF  EF
  SCPM UNKN-CDE  IAC EOR
  69   26        FF  EF
  Indications (allowed in the two ways)
  SCPM DATA-IND <FC1> <FC2> STX [<screen-data>]  IAC EOR
  69   00       <FC1> <FC2> 02  [<screen-data>]  FF  EF
  SCPM PURGE  IAC EOR
  69   28     FF  EF

13. Security Considerations

 Security issues are not addressed in this document.  It is
 anticipated that once authentication mechanisms have become well
 established, use of them can be made by TNVIP.  One of the important
 uses of authentication would be to answer the question of whether or
 not a given user should be allowed to "use" a specific terminal.

Dujonc Informational [Page 29] RFC 1921 TNVIP Protocol March 1996

14. References

 [1] Postel, J., and J. Reynolds, "Telnet Protocol Specification", STD
     8, RFC 854, USC/Information Sciences Institute, May 1983.
 [2] "Communications. MainWay. Terminal Management. DNS-E",
     Ref : 39A213EB Rev00, BULL S.A.
 [3] VanBokkelen, J., "Telnet Terminal-Type Option", RFC 1091, FTP
     Software, Inc., February 1989.
 [4] Postel, J., "Telnet End of Record Option", RFC 885,
     USC/Information Sciences Institute, December 1983.
 [5] Postel, J., and J. Reynolds, "Telnet Binary Transmission", STD
     27, RFC 856, USC/Information Sciences Institute, May 1983.
 [6] Postel, J., and J. Reynolds, "Telnet Suppress Go Ahead Option",
     STD 29, RFC 858, USC/Information Sciences Institute, May 1983.
 [7] "Affinity V2. DKU7107 Reference Manual"
     Ref : 40 A2 23 WA, BULL S.A.
 [8] "Affinity V2. VIP7800 Reference Manual"
     Ref : 40 A2 24 WA,  BULL S.A.
 [9] "Bull Questar 200. TCS 7424 et TCS 7434. Transmission de donnees.
     Manuel de  reference"
     Ref : 80 F2 41DC Rev0,  BULL S.A.

15. Author's Address

 Jean-Yves Dujonc
 BULL S.A.
 rue Jean Jaures
 78340 Les Clayes-sous-Bois
 France
 Phone: 1 30 80 62 95
 Fax:   1 30 80 65 40
 EMail: J.Y.Dujonc@frcl.bull.fr

Dujonc Informational [Page 30]

/data/webs/external/dokuwiki/data/pages/rfc/rfc1921.txt · Last modified: 1996/03/21 18:13 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki