rfc2877.txt
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Network Working Group T. Murphy, Jr.
Request for Comments: 2877 P. Rieth
Category: Informational J. Stevens
Updates: 1205 IBM Corporation
July 2000
5250 Telnet Enhancements
Status of this Memo
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.
Murphy, et al. Informational [Page 1]
RFC 2877 5250 Telnet Enhancements July 2000
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
Murphy, et al. Informational [Page 2]
RFC 2877 5250 Telnet Enhancements July 2000
1. Enhancing Telnet Negotiations
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.
2. Standard Telnet Option Negotiation
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:
Murphy, et al. Informational [Page 3]
RFC 2877 5250 Telnet Enhancements July 2000
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.
AS/400 Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 18 -->
<-- FF FB 18
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 -->
<-- FF FB 19
<-- FF FD 19
FF FB 19 -->
.
.
(other negotiations) .
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.
3. Enhanced Telnet Option Negotiation
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.
Murphy, et al. Informational [Page 4]
RFC 2877 5250 Telnet Enhancements July 2000
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.
AS/400 Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 27
FF FD 18 -->
(2 requests bundled)
<-- FF FB 27
FF FA 27 01 00 FF F0 -->
Murphy, et al. Informational [Page 5]
RFC 2877 5250 Telnet Enhancements July 2000
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
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