Current Limitations of TN3270
  
PSS ID Number: Q138483
Article last modified on 11-01-1995
 
2.11
 
WINDOWS
 

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The information in this article applies to:
 
 - Microsoft SNA Server for Windows NT, version 2.11
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SUMMARY
=======
 
TN3270 Server provides access to IBM Mainframes for TN3270 clients using
TCP/IP as the network transport.
 
In regards to this fact, RFC 1576 states the following:
 
"Existing complex IBM 3270 display terminal networks are not easily
integrated with the increasing number of multi-platform networking
environments, specifically TCP/IP. These complex networks include
terminals attached to a 3270 host using SNA (Systems Network
Architecture) and non-SNA connections. To address the issue of easily
connecting display terminals to 3270 hosts using IP networks, several
vendors have introduced telnet servers that provide TCP/IP users a
connection to existing IBM mainframes by supporting display terminal
emulation using a subset of the existing telnet protocol. Telnet
servers may exist on the host itself, or be connected to the host
using SNA or non-SNA methods."
 
MORE INFORMATION
================
 
TN3270 Server has the following limitations.
 
 - No printing support.
 - ATTN and SYSREQ keys are not universally supported.
 - There is no mechanism by which the client can access the SNA Bind
   information.
 - TN3270 clients cannot request a specific SNA resource (for example, 3270
   LU)
 
For a more detailed explanation refer to RFC 1647. RFC 1647 also describes
TN3270E which addresses these limitations.
 
Excerpt from RFC 1647:
 
"It provides no capability for Telnet clients to emulate the 328x
class of printers.
 
 - There is no mechanism by which a Telnet client can request that a
   connection be associated with a given 3270 device-name. This can be
   of importance when a terminal session is being established, since
   many host applications behave differently depending on the network
   name of the terminal. In the case of printer emulation, this
   capability is an absolute necessity because a large number of host
   applications have some method of pre-defining printer destinations.
 
 - The 3270 ATTN and SYSREQ keys are not universally supported.
 
 - There is no support for the SNA positive/negative response process.
   This is particularly important if printer emulation is to function
   properly, but is also useful for some terminal applications. A
   positive response is used to indicate that the previously received
   data has been successfully processed. A negative response indicates
   some sort of error has occurred while processing the previously
   received data; this could be caused by the host application building
   a 3270 data stream that contains an invalid command, or by a
   mechanical error at the client side, among other things.
 
 - There is no mechanism by which the client can access the SNA Bind
   information. The Bind image contains a detailed description of the
   session between the Telnet server and the host application.
 
 - There is no mechanism by which the server can determine whether a
   client supports 3270 structured fields, or a client can request that
   it receive them."
 
KBCategory: kbnetwork kbinterop
KBSubcategory: ntnetserv ntprotocol
Additional reference words: prodsna 2.11
 
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Copyright Microsoft Corporation 1995.
