This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This memo describes the interface to the IBM 5250 Telnet server that allows client Telnet to request a Telnet terminal or printer session using a specific device name. If a requested device name is not available, a method to retry the request using a new device name is described. Methods to request specific Telnet session settings and auto-signon function are also described.
By allowing a Telnet client to select the device name, the 5250 Telnet server opens the door for applications to set and/or extract useful information about the Telnet client. Some possibilities are 1) selecting a customized device name associated with a particular user profile name for National Language Support or subsystem routing, 2) connecting PC and network printers as clients and 3) auto-signon using clear-text or DES-encrypted password exchange.
Applications may need to use system API's on the AS/400 in order to extract Telnet session settings from the device name description. Refer to the Retrieve Device Description (QDCRDEVD) API described in the AS/400 System API book [3] on how to extract information using the DEVD0600 and DEVD1100 templates.
This memo describes how the IBM 5250 Telnet server supports Work Station Function (WSF) printers using 5250 Display Station Pass- Through. A response code is returned by the Telnet server to indicate success or failure of the WSF printer session.
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Table of Contents
1. Enhancing Telnet Negotiations...................... 3 2. Standard Telnet Option Negotiation................. 3 3. Enhanced Telnet Option Negotiation................. 4 4. Enhanced Display Emulation Support................. 7 5. Enhanced Display Auto-Signon and Password Encryption......................................... 8 5.1 Password Substitutes Processing.............. 12 5.2 Handling passwords of length 9 and 10........ 14 5.3 Example Password Substitute Calculation...... 15 6. Device Name Collision Processing................... 15 7. Enhanced Printer Emulation Support................. 16 8. Telnet Printer Terminal Types...................... 18 9. Telnet Printer Startup Response Record for Printer Emulators.......................................... 20 9.1 Example of a Success Response Record......... 20 9.2 Example of an Error Response Record.......... 21 9.3 Response Codes............................... 22 10. Printer Steady-State Pass-Through Interface........ 23 10.1 Example of a Print Record.................... 25 10.2 Example of a Print Complete Record........... 27 10.3 Example of a Null Print Record............... 27 11. End-to-End Print Example........................... 28 12. Authors' Note...................................... 33 13. References......................................... 33 14. Security Considerations............................ 35 15. Authors' Addresses................................. 35 16. Relation to Other RFC's............................ 35 17. Full Copyright Statement........................... 36
LIST OF FIGURES
Figure 1. Example of a success status response record....................................... 20 Figure 2. Example of an error response record.......... 21 Figure 3. Layout of the printer pass-through header....................................... 23 Figure 4. Server sending client data with a print record....................................... 26 Figure 5. Client sending server a print complete record....................................... 27 Figure 6. Server sending client a null print record....................................... 28
The 5250 Telnet server enables clients to negotiate both terminal and printer device names through Telnet Environment Options Negotiations, defined in the Standards Track RFC 1572 [13].
The purpose of RFC 1572 is to exchange environment information using a set of standard or custom variables. By using a combination of both standard VAR's and custom USERVAR's, the 5250 Telnet server allows client Telnet to request a pre-defined specific device by name.
If no pre-defined device exists then the device will be created, with client Telnet having the option to negotiate device attributes, such as the code page, character set, keyboard type, etc.
Since printers can now be negotiated as a device name, new terminal types have been defined to request printers. For example, you can now negotiate "IBM-3812-1" and "IBM-5553-B01" as valid TERMINAL-TYPE options [11].
Finally, the 5250 Telnet server will allow exchange of user profile and password information, where the password may be in either clear- text or encrypted form. If a valid combination of profile and password is received, then the client is allowed to bypass the sign- on panel. The setting of the QRMTSIGN system value must be either *VERIFY or *SAMEPRF for the bypass of the sign-on panel to succeed.
Telnet server option negotiation typically begins with the issuance, by the server, of an invitation to engage in terminal type negotiation with the Telnet client (DO TERMINAL-TYPE) [11]. The client and server then enter into a series of sub-negotiations to determine the level of terminal support that will be used. After the terminal type is agreed upon, the client and server will normally negotiate a required set of additional options (EOR [12], BINARY [10], SGA [15]) that are required to support "transparent mode" or full screen 5250/3270 block mode support. As soon as the required options have been negotiated, the server will suspend further negotiations, and begin with initializing the actual virtual device on the AS/400. A typical exchange might start like the following:
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AS/400 Telnet server Enhanced Telnet client -------------------------- ------------------------- IAC DO TERMINAL-TYPE --> <-- IAC WILL TERMINAL-TYPE IAC SB TERMINAL-TYPE SEND IAC SE --> IAC SB TERMINAL-TYPE IS <-- IBM-5555-C01 IAC SE IAC DO EOR --> <-- IAC WILL EOR <-- IAC DO EOR IAC WILL EOR --> . . (other negotiations) .
Actual bytes transmitted in the above example are shown in hex below.
Some negotiations are symmetrical between client and server and some are negotiated in one direction only. Also, it is permissible and common practice to bundle more than one response or request, or combine a request with a response, so the actual exchange may look different in practice to what is shown above.
In order to accommodate the new environment option negotiations, the server will bundle an environment option invitation along with the standard terminal type invitation request to the client.
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A client should either send a negative acknowledgment (WONT NEW- ENVIRON), or at some point after completing terminal-type negotiations, but before completing the full set of negotiations required for 5250 transparent mode, engage in environment option sub-negotiation with the server. A maximum of 1024 bytes of environment strings may be sent to the server. A recommended sequence might look like the following:
AS/400 Telnet server Enhanced Telnet client -------------------------- ------------------------- IAC DO NEW-ENVIRON IAC DO TERMINAL-TYPE --> (2 requests bundled) <-- IAC WILL NEW-ENVIRON IAC SB NEW-ENVIRON SEND VAR IAC SE --> IAC SB NEW-ENVIRON IS VAR "USER" VALUE "JONES" USERVAR "DEVNAME" VALUE "MYDEVICE07" <-- IAC SE <-- IAC WILL TERMINAL-TYPE (do the terminal type sequence first) IAC SB TERMINAL-TYPE SEND IAC SE --> IAC SB TERMINAL-TYPE IS <-- IBM-5555-C01 IAC SE (terminal type negotiations completed) IAC DO EOR --> (server will continue with normal transparent mode negotiations) <-- IAC WILL EOR . . (other negotiations) .
Actual bytes transmitted in the above example are shown in hex below.
FF FA 27 00 00 55 53 45 52 01 4A 4F 4E 45 53 03 44 45 56 4E 41 4D 45 01 4D 59 44 45 56 49 43 45 <-- 30 37 FF F0 <-- FF FB 18 (do the terminal type sequence first) FF FA 18 01 FF F0 --> FF FA 18 00 49 42 4D 2D 35 35 35 35 2D 43 30 31 <-- FF F0 FF FD 19 --> (server will continue with normal transparent mode negotiations) <-- FF FB 19 . . (other negotiations) .
RFC 1572 defines 6 standard VAR's: USER, JOB, ACCT, PRINTER, SYSTEMTYPE, and DISPLAY. The USER standard VAR will hold the value of the AS/400 user profile name to be used in auto-signon requests. The Telnet server will make no direct use of the additional 5 VAR's, nor are any of them required to be sent. All standard VAR's and their values that are received by the Telnet server will be placed in a buffer, along with any USERVAR's received (described below), and made available to a registered initialization exit program to be used for any purpose desired.
There are some reasons you may want to send NEW-ENVIRON negotiations prior to TERMINAL-TYPE negotiations. With AS/400 TELNET server, several virtual device modes can be negotiated: 1) VTxxx device 2) 3270 device 3) 5250 device (includes Network Station). The virtual device mode selected depends on the TERMINAL-TYPE negotiated plus any other TELNET option negotiations necessary to support those modes. The AS/400 TELNET server will create the desired virtual device at the first opportunity it thinks it has all the requested attributes needed to create the device. This can be as early as completion of the TERMINAL-TYPE negotiations.
For the case of Transparent mode (5250 device), then the moment TERMINAL-TYPE, BINARY, and EOR options are negotiated the TELNET server will go create the virtual device. Receiving any NEW-ENVIRON negotiations after these option negotiations are complete will result in the NEW-ENVIRON negotiations having no effect on device attributes, as the virtual device will have already been created.
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So, for Transparent mode, NEW-ENVIRON negotiations are effectively closed once EOR is negotiated, since EOR is generally the last option done.
For other devices modes (such as VTxxx or 3270), you cannot be sure when the AS/400 TELNET server thinks it has all the attributes to create the device. Recall that NEW-ENVIRON negotiations are optional, and therefore the AS/400 TELNET server need not wait for any NEW-ENVIRON options prior to creating the virtual device. It is in the clients best interest to send NEW-ENVIRON negotiations as soon as possible, preferably before TERMINAL-TYPE is negotiated. That way, the client can be sure the requested attributes were received before the virtual device is created.
RFC 1572 style USERVAR variables have been defined to allow a compliant Telnet client more control over the Telnet server virtual device on the AS/400. These USERVAR's allow the client Telnet to create or select a previously created virtual device. If the virtual device does not exist and must be created, then the USERVAR variables are used to create and initialize the device attributes. If the virtual device already exists, the device attributes are modified.
The USERVAR's defined to accomplish this are:
USERVAR VALUE EXAMPLE DESCRIPTION -------- ---------------- ---------------- ------------------- DEVNAME us-ascii char(x) MYDEVICE07 Display device name KBDTYPE us-ascii char(3) USB Keyboard type CODEPAGE us-ascii char(y) 437 Code page CHARSET us-ascii char(y) 1212 Character set
x - up to a maximum of 10 characters y - up to a maximum of 5 characters
For a description of the KBDTYPE, CODEPAGE and CHARSET parameters and their permissible values, refer to Chapter 8 in the Communications Configuration Reference [5] and also to Appendix C in National Language Support [16].
The CODEPAGE and CHARSET USERVAR's must be associated with a KBDTYPE USERVAR. If either CODEPAGE or CHARSET are sent without KBDTYPE, they will default to system values. A default value for KBDTYPE can be sent to force CODEPAGE and CHARSET values to be used.
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AS/400 system objects such as device names, user profiles, clear-text passwords, programs, libraries, etc. are required to be specified in English Upper Case (EUC). This includes:
Any letter (A-Z), any number (0-9), special characters (# $ _ @)
Therefore, where us-ascii is specified for VAR or USERVAR values, it is recommended that upper-cased ASCII values be sent, which will be converted to EBCDIC by the Telnet server.
A special case occurs for encrypted passwords (described in the next section), where both the initial password and user profile used to build the encrypted password must be EBCDIC English Upper Case, in order to be properly authenticated by the Telnet server.
5. Enhanced Display Auto-Signon and Password Encryption
Several 5250 Telnet server specific USERVAR's will be defined. One will carry a random seed to be used in Data Encryption Standard (DES) password encryption, and another will carry the encrypted copy of the password. This would use the same 7-step DES-based password substitution scheme as APPC and Client Access. For a description of DES encryption, refer to Federal Information Processing Standards Publications (FIPS) 46-2 [17] and 81 [18], which can be found at the Federal Information Processing Standards Publications link:
If encrypted password exchange is not required, clear-text password exchange is permitted using the same USERVAR's defined for encryption. For this case, the random client seed should be set to either an empty value (RFC 1572 preferred method) or to hexadecimal zeros to indicate the password is not encrypted, but is clear-text.
It should be noted that security of clear-text password exchange cannot be guaranteed unless the network is physically protected or a trusted network (such as an intranet). If your network is vulnerable to IP address spoofing or directly connected to the Internet, you should engage in encrypted password exchange to validate a clients identity.
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Additional VAR's and USERVAR's have also been defined to allow an auto-signon user greater control over their startup environment, similar to what is supported using the Open Virtual Terminal (QTVOPNVT) API [3].
The standard VAR's supported to accomplish this are:
VAR VALUE EXAMPLE DESCRIPTION -------- ---------------- ---------------- ------------------- USER us-ascii char(x) USERXYZ User profile name
x - up to a maximum of 10 characters
The custom USERVAR's defined to accomplish this are:
USERVAR VALUE EXAMPLE DESCRIPTION -------- ---------------- ---------------- ------------------- IBMRSEED binary(8) 8-byte hex field Random client seed IBMSUBSPW binary(10) 10-byte hex field Substitute password IBMCURLIB us-ascii char(x) QGPL Current library IBMIMENU us-ascii char(x) MAIN Initial menu IBMPROGRAM us-ascii char(x) QCMD Program to call
x - up to a maximum of 10 characters
In order to communicate the server random seed value to the client, the server will request a USERVAR name made up of a fixed part (the 8 characters "IBMRSEED" immediately followed by an 8-byte hexadecimal variable part, which is the server random seed. The client generates its own 8-byte random seed value, and uses both seeds to encrypt the password. Both the encrypted password and the client random seed value are then sent to the server for authentication. RFC 1572 rules will need to be adhered to when transmitting the client random seed and substituted password values to the server. Specifically, since a typical environment string is a variable length hexadecimal field, the hexadecimal fields are required to be escaped and/or byte stuffed according to the RFC 854 [8], where any single byte could be mis- construed as a Telnet IAC or other Telnet option negotiation control character. The client must escape and/or byte stuff any bytes which could be seen as a RFC 1572 [13] option, specifically VAR, VALUE, ESC and USERVAR.
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The following illustrates the encrypted case:
AS/400 Telnet server Enhanced Telnet client -------------------------- ------------------------------- IAC DO NEW-ENVIRON --> <-- IAC WILL NEW-ENVIRON IAC SB NEW-ENVIRON SEND USERVAR "IBMRSEEDxxxxxxxx" USERVAR "IBMSUBSPW" VAR USERVAR IAC SE --> IAC SB NEW-ENVIRON IS VAR "USER" VALUE "DUMMYUSR" USERVAR "IBMRSEED" VALUE "yyyyyyyy" USERVAR "IBMSUBSPW" VALUE "zzzzzzzz" <-- IAC SE . . (other negotiations) .
In this example, "xxxxxxxx" is an 8-byte hexadecimal random server seed, "yyyyyyyy" is an 8-byte hexadecimal random client seed and "zzzzzzzz" is an 8-byte hexadecimal encrypted password. If the password is not valid, then the sign-on panel is displayed. If the password is expired, then the Change Password panel is displayed.
Actual bytes transmitted in the above example are shown in hex below, where the server seed is "7D3E488F18080404", the client seed is "4E4142334E414233" and the encrypted password is "DFB0402F22ABA3BA". The user profile used to generate the encrypted password is "44554D4D59555352" (DUMMYUSR), with a clear-text password of "44554D4D595057" (DUMMYPW).
53 55 42 53 50 57 01 DF B0 40 2F 22 AB A3 BA FF <-- F0
The following illustrates the clear-text case:
AS/400 Telnet server Enhanced Telnet client -------------------------- ------------------------- IAC DO NEW-ENVIRON --> <-- IAC WILL NEW-ENVIRON IAC SB NEW-ENVIRON SEND USERVAR "IBMRSEEDxxxxxxxx" USERVAR "IBMSUBSPW" VAR USERVAR IAC SE --> IAC SB NEW-ENVIRON IS VAR "USER" VALUE "DUMMYUSR" USERVAR "IBMRSEED" VALUE USERVAR "IBMSUBSPW" VALUE "yyyyyyyy" <-- IAC SE . . (other negotiations) .
In this example, "xxxxxxxx" is an 8-byte hexadecimal random server seed, "yyyyyyyyyy" is a 10-byte us-ascii client clear-text password. If the password has expired, then the sign-on panel is displayed.
Actual bytes transmitted in the above example are shown in hex below, where the server seed is "7D3E488F18080404", the client seed is empty and the clear-text password is "44554D4D595057" (DUMMYPW). The user profile used is "44554D4D59555352" (DUMMYUSR).
Both APPC and Client Access use well-known DES encryption algorithms to create encrypted passwords. A Network Station or Enhanced Client can generate compatible encrypted passwords if they follow these steps, details of which can be found in the Federal Information Processing Standards 46-2 [17].
1. Padded_PW = Left justified user password padded to the right with '40'X to 8 bytes.
The users password must be left justified in an 8 byte variable and padded to the right with '40'X up to an 8 byte length. If the users password is 8 bytes in length, no padding would occur. For computing password substitutes for passwords of length 9 and 10 see section "Handling passwords of length 9 and 10" below. Passwords less than 1 byte or greater than 10 bytes in length are not valid. Please note, if password is not in EBCDIC, it must be converted to EBCDIC uppercase.
2. XOR_PW = Padded_PW xor '5555555555555555'X
The padded password is Exclusive OR'ed with 8 bytes of '55'X.
3. SHIFT_RESULT = XOR_PW << 1
The entire 8 byte result is shifted 1 bit to the left; the leftmost bit value is discarded, and the rightmost bit value is cleared to 0.
This shifted result is used as key to the Data Encryption Standard (Federal Information Processing Standards 46-2 [17]) to encipher the user identifier. When the user identifier is less than 8 bytes, it is left justified in an 8 byte variable and padded to the right with '40'X. When the user identifier is 9 or 10 bytes, it is first padded to the right with '40'X to a length of 10 bytes. Then bytes 9 and 10 are "folded" into bytes 1-8 using the following algorithm:
Bit 0 is the high-order bit (i.e. has value of '80'X).
Byte 1, bits 0 and 1 are replaced with byte 1, bits 0 and 1 Exclusive OR'ed with byte 9, bits 0 and 1. Byte 2, bits 0 and 1 are replaced with byte 2, bits 0 and 1 Exclusive OR'ed with byte 9, bits 2 and 3.
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Byte 3, bits 0 and 1 are replaced with byte 3, bits 0 and 1 Exclusive OR'ed with byte 9, bits 4 and 5. Byte 4, bits 0 and 1 are replaced with byte 4, bits 0 and 1 Exclusive OR'ed with byte 9, bits 6 and 7. Byte 5, bits 0 and 1 are replaced with byte 5, bits 0 and 1 Exclusive OR'ed with byte 10, bits 0 and 1. Byte 6, bits 0 and 1 are replaced with byte 6, bits 0 and 1 Exclusive OR'ed with byte 10, bits 2 and 3. Byte 7, bits 0 and 1 are replaced with byte 7, bits 0 and 1 Exclusive OR'ed with byte 10, bits 4 and 5. Byte 8, bits 0 and 1 are replaced with byte 8, bits 0 and 1 Exclusive OR'ed with byte 10, bits 6 and 7.
User identifier greater than 10 bytes or less than 1 byte are not the result of this encryption id known as PW_TOKEN in the paper.
5. Increment PWSEQs and store it.
Each LU must maintain a pair of sequence numbers for ATTACHs sent and received on each session. Each time an ATTACH is generated, (and password substitutes are in use on the session) the sending sequence number, PWSEQs, is incremented and saved for the next time. Both values are set to zero at BIND time. So the first use of PWSEQs has the value of 1, and increases by one with each use. A new field is added to the ATTACH to carry this sequence number. However, in certain error conditions, it is possible for the sending side to increment the sequence number and the receiver may not increment it. When the sender sends a subsequent ATTACH, the receiver will detect a missing sequence. This is allowed. However the sequence number received must always be larger than the previous one, even if some are missing.
The maximum number of consecutive missing sequence numbers allowed is 16. If this is exceeded, the session is unbound with a protocol violation.
Note: The sequence number must be incremented for every ATTACH sent. However, the sequence number field is only required to be included in the FMH5 if a password substitute is sent (byte 4, bit 3 on).
6. RDrSEQ = RDr + PWSEQs /* RDr is server seed. */
The current value of PWSEQs is added to RDr, the random value received from the partner LU on this session, yielding RDrSEQ, essentially a predictably modified value of the random value received from the partner LU at BIND time.
The PW_TOKEN is used as a key to the DES function to generate a 8 bytes value for the following string of inputs. The DES CBC mode Initialization Vector (IV) used is 8 bytes of '00'X.
RDrSEQ: the random data value received from the partner LU plus the sequence number.
RDs: the random data value sent to the partner LU on BIND for this session.
A 16 byte value created by:
- padding the user identifier with '40'X to a length of 16 bytes.
- Exclusive OR the two 8 byte halves of the padded user identifier with the RDrSEQ value.
Note: User ID must first be converted to EBCDIC upper case.
PWSEQs: the sequence number.
This is similar to the process used on LU-LU verification as described in the Enhanced LU-LU Bind Security. The resulting enciphered random data is the 'password substitute'.
1. Generate PW_TOKENa by using characters 1 to 8 of the password and steps 1-4 from the previous section.
2. Generate PW_TOKENb by using characters 9 and 10 and steps 1-4 from the previous section. In this case Padded_PW from step 1 will be characters 9 and 10 padded to the right with '40'X, for a total length of 8.
3. PW_TOKEN = PW_TOKENa xor PW_TOKENb
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4. Now compute PW_SUB by performing steps 5-7 from the previous section.
ID: USER123 Password: ABCDEFG Server seed: '7D4C2319F28004B2'X Client seed: '08BEF662D851F4B1'X PWSEQs: 1 (PWSEQs is a sequence number needed in the 7-step encryption, and it is always one)
Encrypted Password should be : '5A58BD50E4DD9B5F'X
6. Device Name Collision Processing
Device name collision occurs when a Telnet client sends the Telnet server a virtual device name that it wants to use, but that device is already in use on the server. When this occurs, the Telnet server sends a request to the client asking it to try another device name. The environment option negotiation uses the USERVAR name of DEVNAME to communicate the virtual device name. The following shows how the Telnet server will request the Telnet client to send a different DEVNAME when device name collision occurs.
AS/400 Telnet server Enhanced Telnet client -------------------------- ------------------------- IAC SB NEW-ENVIRON SEND VAR USERVAR IAC SE -->
Server requests all environment variables be sent.
IAC SB NEW-ENVIRON IS USERVAR "DEVNAME" VALUE "MYDEVICE1" USERVAR "xxxxx" VALUE "xxx" ... <-- IAC SE
Client sends all environment variables, including DEVNAME. Server tries to select device MYDEVICE1. If the device is already in use, server requests DEVNAME be sent again.
IAC SB NEW-ENVIRON SEND USERVAR "DEVNAME" IAC SE -->
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Server sends a request for a single environment variable: DEVNAME
IAC SB NEW-ENVIRON IS USERVAR <-- "DEVNAME" VALUE "MYDEVICE2" IAC SE
Client sends one environment variable, calculating a new value of MYDEVICE2. If MYDEVICE2 is different from the last request, then server tries to select device MYDEVICE2, else server disconnects client. If MYDEVICE2 is also in use, server will send DEVNAME request again, and keep doing so until it receives a device that is not in use, or the same device name twice in row.
RFC 1572 style USERVAR variables have been defined to allow a compliant Telnet client more control over the Telnet server virtual device on the AS/400. These USERVAR's allow the client Telnet to select a previously created virtual device or auto-create a new virtual device with requested attributes.
This makes the enhancements available to any Telnet client that chonoses to support the new negotiations.
The USERVAR's defined to accomplish this are:
USERVAR VALUE EXAMPLE DESCRIPTION ------------- ---------------- ---------------- ------------------- DEVNAME us-ascii char(x) PRINTER1 Printer device name IBMIGCFEAT us-ascii char(6) 2424J0 IGC feature (DBCS) IBMMSGQNAME us-ascii char(x) QSYSOPR *MSGQ name IBMMSGQLIB us-ascii char(x) QSYS *MSGQ library IBMFONT us-ascii char(x) 12 Font IBMFORMFEED us-ascii char(1) C | U | A Formfeed IBMTRANSFORM us-ascii char(1) 1 | 0 Transform IBMMFRTYPMDL us-ascii char(x) *IBM42023 Mfg. type and model IBMPPRSRC1 binary(1) 1-byte hex field Paper source 1 IBMPPRSRC2 binary(1) 1-byte hex field Paper source 2 IBMENVELOPE binary(1) 1-byte hex field Envelope hopper IBMASCII899 us-ascii char(1) 1 | 0 ASCII 899 support IBMWSCSTNAME us-ascii char(x) *NONE WSCST name IBMWSCSTLIB us-ascii char(x) *LIBL WSCST library
x - up to a maximum of 10 characters
The "IBM" prefix on the USERVAR's denotes AS/400 specific attributes.
The DEVNAME USERVAR is used both for displays and printers. The IBMFONT and IBMASCII899 are used only for SBCS environments.
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For a description of most of these parameters (drop the "IBM" from the USERVAR) and their permissible values, refer to Chapter 8 in the Communications Configuration Reference [5].
The IBMIGCFEAT supports the following variable DBCS language identifiers in position 5 (positions 1-4 must be '2424', position 6 must be '0'):
'J' = Japanese 'K' = Korean 'C' = Traditional Chinese 'S' = Simplified Chinese
The IBMTRANSFORM and IBMASCII899 values correspond to:
'1' = Yes '2' = No
The IBMFORMFEED values correspond to:
'C' = Continuous 'U' = Cut 'A' = Autocut
The IBMPPRSRC1, IBMPPRSRC2 and IBMENVELOPE custom USERVAR's do not map directly to their descriptions in Chapter 8 in the Communications Configuration Reference [5]. To map these, use the index listed here:
New Telnet options are defined for the printer pass-through mode of operation. To enable printer pass-through mode, both the client and server must agree to at least support the Transmit-Binary, End-Of- Record, and Terminal-Type Telnet options. The following are new terminal types for printers:
Specific characteristics of the IBM-5553-B01 or IBM-3812-1 printers are specified through the USERVAR IBMMFRTYPMDL, which specifies the manufacturer type and model.
An example of a typical negotiation process to establish printer pass-through mode of operation is shown below. In this example, the server initiates the negotiation by sending the DO TERMINAL-TYPE request.
For DBCS environments, if IBMTRANSFORM is set to 1 (use Host Print Transform), then the virtual device created is 3812, not 5553. Therefore, IBM-3812-1 should be negotiated for TERMINAL-TYPE, and not IBM-5553-B01.
AS/400 Telnet server Enhanced Telnet client -------------------------- -------------------------- IAC DO NEW-ENVIRON --> <-- IAC WILL NEW-ENVIRON IAC SB NEW-ENVIRON SEND VAR USERVAR IAC SE --> IAC SB NEW-ENVIRON IS USERVAR "DEVNAME" VALUE "PCPRINTER" USERVAR "IBMMSGQNAME" VALUE "QSYSOPR" USERVAR "IBMMSGQLIB" VALUE "*LIBL" USERVAR "IBMTRANSFORM" VALUE "0" USERVAR "IBMFONT" VALUE "12" USERVAR "IBMFORMFEED" VALUE "C" USERVAR "IBMPPRSRC1" VALUE ESC '01'X USERVAR "IBMPPRSRC2" VALUE '04'X USERVAR "IBMENVELOPE" VALUE IAC 'FF'X <-- IAC SE IAC DO TERMINAL-TYPE --> <-- IAC WILL TERMINAL-TYPE IAC SB TERMINAL-TYPE SEND IAC SE -->
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IAC SB TERMINAL-TYPE IS IBM-3812-1 <-- IAC SE IAC DO BINARY --> <-- IAC WILL BINARY IAC DO EOR --> <-- IAC WILL EOR
Some points about the above example. The IBMPPRSRC1 value requires escaping the value using ESC according to RFC 1572 [13]. The IBMPPRSRC2 does not require an ESC character since '04'X has no conflict with RFC 1572 options. Finally, to send 'FF'X for the IBMENVELOPE value, escape the 'FF'X value by using another 'FF'X (called "doubling"), so as not to have the value interpreted as a Telnet character per RFC 854 [8].
Actual bytes transmitted in the above example are shown in hex below.
9. Telnet Printer Startup Response Record for Printer Emulators
Once Telnet negotiation for a 5250 pass-through mode is completed, the 5250 Telnet server will initiate a virtual printer power-on sequence on behalf of the Telnet client. The Telnet server will supply a Startup Response Record to the Telnet client with the status of the printer power-on sequence, indicating success or failure of the virtual printer power-on sequence.
This section shows an example of two Startup Response Records. The source device is a type 3812 model 01 printer with name "PCPRINTER" on the target system "TARGET".
Figure 1 shows an example of a successful response; Figure 2 shows an example of an error response.
The response record in Figure 1 was sent by an AS/400 at Release V4R2. It is an example of the target sending back a successful Startup Response Record.
+------------------------------------------------------------------+ | +----- Pass-Through header | | | +--- Response data | | | | +---- Start diagnostic information| | | | | | | +----------++----------++--------------------------------------- | | | || || | | 004912A090000560060020C0003D0000C9F9F0F2E3C1D9C7C5E34040D7C3D7D9 | | | | T A R G E T P C P R | | +------+ | | Response Code (I902) | | | | ---------------------------------------------------------------- | | | | C9D5E3C5D9400000000000000000000000000000000000000000000000000000 | | I N T E R | | | | +------- End of diagnostic information | | | | | -----------------+ | | | | | 000000000000000000 | +------------------------------------------------------------------+ Figure 1. Example of a success response record.
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- '0049'X = Length pass-through data, including this length field - '12A0'X = GDS LU6.2 header - '90000560060020C0003D0000'X = Fixed value fields - 'C9F9F0F2'X = Response Code (I902) - 'E3C1D9C7C5E34040'X = System Name (TARGET) - 'D7C3D7D9C9D5E3C5D940'X = Object Name (PCPRINTER)
The response record in Figure 2 is one that reports an error. The virtual device named "PCPRINTER", is not available on the target system "TARGET", because the device is not available. You would normally see this error if the printer was already assigned to another Telnet session.
+------------------------------------------------------------------+ | +----- Pass-Through header | | | +--- Response data | | | | +---- Start diagnostic information| | | | | | | +----------++----------++--------------------------------------- | | | || || | | 004912A09000056006008200003D0000F8F9F0F2E3C1D9C7C5E34040D7C3D7D9 | | | | T A R G E T P C P R | | +------+ | | Response Code (8902) | | | | ---------------------------------------------------------------- | | | | C9D5E3C5D9400000000000000000000000000000000000000000000000000000 | | I N T E R | | | | +------- End of diagnostic information | | | | | -----------------+ | | | | | 000000000000000000 | +------------------------------------------------------------------+ Figure 2. Example of an error response record.
- '0049'X = Length pass-through data, including this length field - '12A0'X = GDS LU6.2 header - '90000560060020C0003D0000'X = Fixed value fields - 'F8F9F0F2'X = Response Code (8902) - 'E3C1D9C7C5E34040'X = System Name (TARGET) - 'D7C3D7D9C9D5E3C5D940'X = Object Name (PCPRINTER)
The Start-Up Response Record success response codes:
CODE DESCRIPTION ---- ------------------------------------------------------ I901 Virtual device has less function than source device I902 Session successfully started I906 Automatic sign-on requested, but not allowed. Session still allowed; a sign-on screen will be coming.
The Start-Up Response Record error response codes:
CODE DESCRIPTION ---- ------------------------------------------------------ 2702 Device description not found. 2703 Controller description not found. 2777 Damaged device description. 8901 Device not varied on. 8902 Device not available. 8903 Device not valid for session. 8906 Session initiation failed. 8907 Session failure. 8910 Controller not valid for session. 8916 No matching device found. 8917 Not authorized to object. 8918 Job canceled. 8920 Object partially damaged. 8921 Communications error. 8922 Negative response received. 8923 Start-up record built incorrectly. 8925 Creation of device failed. 8928 Change of device failed. 8929 Vary on or vary off failed. 8930 Message queue does not exist. 8934 Start-up for S/36 WSF received. 8935 Session rejected. 8936 Security failure on session attempt. 8937 Automatic sign-on rejected. 8940 Automatic configuration failed or not allowed. I904 Source system at incompatible release.
BYTES 0-1: Length of structure including this field (LLLL)
BYTES 2-3: GDS Identifier ('12A0'X)
BYTE 4-5: Data flow record
This field contains flags that describe what type of data pass-through should expect to find following this header. Generally, bits 0-2 in the first byte are mutually exclusive (that is, if one of them is set to ' 1'B, the rest will be set to '0'B.) The bits, and their meanings follow.
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BIT DESCRIPTION
0 Start-Up confirmation 1 Termination record 2 Start-Up Record 3 Diagnostic information included 4 - 5 Reserved 6 Reserved 7 Printer record 8 - 13 Reserved 14 Client-originated (inbound) printer record 15 Server-originated (outbound) printer record
BYTE 6: Length printer pass-through header including this field (LL)
BYTES 7-8: Flags
BYTE 7 BITS: xxxx x111 --> Reserved xxxx 1xxx --> Last of chain xxx1 xxxx --> First of chain xx1x xxxx --> Printer now ready x1xx xxxx --> Intervention Required 1xxx xxxx --> Error Indicator
If BYTE 7 = xx1x xxxx then bytes 10-LL may contain: Printer ready C9 00 00 00 02
If BYTE 7 = x1xx xxxx then bytes 10-LL may contain: (2) Command/parameter not valid C9 00 03 02 2x Print check C9 00 03 02 3x Forms check C9 00 03 02 4x Normal periodic condition C9 00 03 02 5x Data stream error C9 00 03 02 6x Machine/print/ribbon check C9 00 03 02 8x
If BYTE 7 = 1xxx xxxx then bytes 10-LL may contain: (3) Cancel 08 11 02 00 Invalid print parameter 08 11 02 29
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Invalid print command 08 11 02 28
Diagnostic information notes:
1. LL is the length of the structure defined in Byte 6. If no additional data is present, the remainder of the structure must be padded with zeroes.
2. These are printer SIGNAL commands. Further information on these commands may be obtained from the 5494 Remote Control Unit Functions Reference guide [2]. Refer to your AS/400 printer documentation for more specific information on these data stream exceptions. Some 3812 and 5553 errors that may be seen:
Machine check C9 00 03 02 11 Graphics check C9 00 03 02 26 Print check C9 00 03 02 31 Form jam C9 00 03 02 41 Paper jam C9 00 03 02 47 End of forms C9 00 03 02 50 Printer not ready C9 00 03 02 51 Data stream - class 1 C9 00 03 02 66 loss of text Data stream - class 2 C9 00 03 02 67 text appearance Data stream - class 3 C9 00 03 02 68 multibyte control error Data stream - class 4 C9 00 03 02 69 multibyte control parm Cover unexpectedly open C9 00 03 02 81 Machine check C9 00 03 02 86 Machine check C9 00 03 02 87 Ribbon check C9 00 03 02 88
3. These are printer negative responses. Further information on these commands may be obtained from the 5494 Remote Control Unit Functions Reference guide [2].
Figure 4 shows the server sending the client data with a print record. This is normally seen following receipt of a Success Response Record, such as the example in Figure 1.
- '0085'X = Logical record length, including this byte (LLLL) - '12A0'X = GDS LU6.2 header - '0101'X = Data flow record (server to client) - '0A'X = Length of pass-through specific header (LL) - '1800'X = First of chain / Last of chain indicators - '01'X = Print - '000000000000'X = Zero pad header to LL specified - '34C401'X = First piece of data for spooled data - Remainder is printer data/commands/orders
Figure 5 shows the client sending the server a print complete record. This would normally follow receipt of a print record, such as the example in Figure 4. This indicates successful completion of a print request.
- '000A'X = Logical record length, including this byte (LLLL) - '12A0'X = GDS LU6.2 header - '0102'X = Data flow response record (client to server) - '04'X = Length of pass-through specific header (LL) - '0000'X = Good Response - '01'X = Print Complete
Figure 6 shows the server sending the client a null print record. The null print record is the last print command the server sends to the client for a print job, and indicates to the printer there is no more data. The null data byte '00'X is optional, and in some cases may be omitted (in particular, this scenario occurs in DBCS print streams).
This example would normally follow any number of print records, such as the example in Figure 4. This indicates successful completion of a print job. The client normally responds to this null print record with another print complete record, such as in Figure 5.
- '0011'X = Logical record length, including this byte - '12A0'X = GDS LU6.2 header - '0101'X = Data flow record - '0A'X = Length of pass-through specific header (LL) - '0800'X = Last of Chain - '01'X = Print - '000000000000'X = Zero pad header to LL specified - '00'X = Null data byte
The next example shows a full print exchange between a Telnet client and server for a 526 byte spooled file. Selective translation of the hexadecimal streams into 1) Telnet negotiations and 2) ASCII/EBCDIC characters are done to aid readability. Telnet negotiations are delimited by '(' and ')' parenthesis characters; ASCII/EBCDIC conversions are bracketed by '|' vertical bar characters.
AS/400 Telnet server Enhanced Telnet client ------------------------------- --------------------------------- FFFD27 -->
(IAC SB NEW-ENVIRON IS USERVAR IBMRSEED xxxxxxxx VAR USERVAR DEVNAME VALUE DUMMYPRT USERVAR IBMMSGQNAME VALUE QSYSOPR USERVAR IBMMSGQLIB VALUE *LIBL USERVAR IBMFONT VALUE 11 USERVAR IBMTRANSFORM VALUE 1 USERVAR IBMMFRTYPMDL VALUE *HPII USERVAR IBMPPRSRC1 VALUE ESC '01'X USERVAR IBMPPRSRC2 VALUE '04'X USERVAR IBMENVELOPE VALUE IAC USERVAR IBMASCII899 VALUE 0 IAC SE)
<-- FFFA180049424D2D 333831322D31FFF0
(IAC SB TERMINAL-TYPE IS IBM-3812-1 IAC SE) FFFD19 -->
Discussion of this memo should occur in one of these mailing lists:
TN3270E List (Roger Fajman raf@cu.nih.gov). Send subscription requests as e-mail with "subscribe tn3270e your_full_name" to listserv@list.nih.gov.
Midrange-L List (David Gibbs david@midrange.com). Send subscription requests as email with "subscribe midrange-l your_internet_address" to majordomo@midrange.com.
Telnet Working Group Mailing List: Send subscription requests as email with "subscribe telnet-ietf" to telnet-ietf- request@bsdi.com.
This memo is an update to RFC 1205 [14], which describes the 5250 Telnet Interface. This update enhances that description to include device negotiation as well as printer support.
This memo makes use of RFC 1572 [13] to enhance communications with 5250 Telnet clients. RFC 1572 is currently on the Standards Track as a Proposed Standard, and is listed in Assigned Numbers [19].
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