Using 3270 Applications through IPSANET

David Chivers, Manager of IPSANET Development, London

Configuration of an SDLC Pipeline

IPSANET provides a cost-effective alternative to dedicated leased lines when linking IBM 3270 terminals in remote sites to a mainframe in a distant location. Very many application programs, whether written in SHARP APL or not, are designed for use only with IBM 3270 display terminals.

IPSANET is particularly effective in providing access to these programs across national boundaries or where traffic volumes are low. To illustrate, let's look at the alternatives in use at I. P. Sharp to meet our own internal needs.

Our 3270 user community consists of three main groups:

’ĢEnd users of 3270-based application packages such as VIEWPOINT, who use it extensively from all IPSA offices worldwide. Our internal Management Information Systems group has many systems written in VIEWPOINT. Users of these applications include IPSA sales and support staff as well as those working on development and support.

’Ģ Our Software Development group who needs access to other systems such as TSO. They are based at a small number of major offices, but also work from time to time at other offices or client sites.

’ĢThose who prefer to work with 3270 terminals when available.

IPSA operates a small SNA network, using IBM's standard network offerings, which provides access to our production and development mainframes in Toronto. The SNA network serves a number of 3270 terminals in the Toronto office. It is extended by leased lines to a few client offices, and also serves 3270 users in our Rochester and Palo Alto offices.

The remote links to Rochester and Palo Alto are provided through IPSANET via a network (SDLC) pipeline.

The beauty of this scheme is that no special changes are required to the normal SNA network configuration to support these remote 3270 users; as far as the IBM software is concerned, these users are connected through leased lines. The users in Palo Alto and Rochester observe no degradation in performance when connected through IPSANET instead of a dedicated leased line.

3270 terminal emulation

When the overhead associated with the support of true 3270s isn't justified, an IBM Personal Computer or HDS108 terminal can be used to emulate a 3270. (The PC is operated in HDS mode, using the IPSA software product NWS3270/PC.)

To make an HDS or PC emulating an HDS look and behave like a 3278 requires some software on the mainframe. For access to sharp APL applications such as VIEWPOINT, we use another IPSA software product called Network Station (NWS) on the mainframe. The result is that 3270 applications can be run cost-effectively by someone with a PC or HDS sitting halfway around the world using IPSANET.

HDS3278, an IPSA product similar to NWS, also allows access to SHARP APL. Unlike NWS, however, HDS3278 allows access to any VTAM application, such as TSO. The IPSA product, AVAM, provides a path between the HDS3278 and these VTAM applications.

What of the future?

We expect continued and increasing demand for ipsanet access to 3270 applications. Several enhancements are being considered. One is to rewrite the functions of HDS3278 as part of the SHARP apl system software, thus increasing its efficiency. Another is to enhance the scope of the emulation both at the PC and at the mainframe to include 3279 emulation, and therefore, colour; and also to provide error correction in the asynchronous connection between the terminal and the network.

Finally, as part of the Net 90 development mentioned in the previous article, we expect to include the terminal emulation capability as part of the function of an ipsanet network node. This would allow 3270-like access to any system, whether or not a SHARP APL system was installed. Net 90 will also be instrumental in allowing us to enhance our network pipeline offerings over IPSANET, making them more cost-effective.