Opening up your SNA or other legacy applications to the Web is a little like losing your baby teeth: It will be a little painful at first, but it's becoming a rite of passage for many enterprise networks.
Plenty of companies are going through this application extension process these days, buying into the conventional wisdom that IP-based networks are more open and less expensive to operate than older networks, such as those based on IBM's SNA. At the same time, companies that have already made big SNA investments can't just get rid of their precious applications and data without a major code rewrite.
To strike a happy medium, many users are phasing out their legacy networks but are keeping the applications and making them accessible via PCs outfitted with Web browsers. Indeed, market research firm International Data Corp. estimates that by 2002 there will 24.5 million browsers handling Web-to-host sessions, up from 2.3 million today.
However, before a Web-to-host system is launched, there are a number of things to consider: Will the applications be accessible to remote users, local users or both? Does the end user need just a basic 3270 green screen terminal emulation or a sophisticated graphical interface? Is there more than one host to access?
Choices to make Most Web-to-host systems involve a user logging on to a Web server that downloads a Java applet to the client. The applet in turn connects to the appropriate host and the session is established. There are variations on this -- for instance, direct
There are a dozen or more Web-to-host product vendors in the market, ranging from IBM and its SecureWay Host On-Demand product, to mid-size companies, such as OpenConnect and Eicon, to start-ups, such as Ericom and Anota.
"The number of tools out there is mindboggling," says Pete Longden, Internet consultant at CareFirst BlueCross BlueShield, an Owings Mills, Md., health care provider. "Be sure you know what your requirements are and what you expect from the tool."
Longden says Web-to-host designers must have a thorough understanding of the underlying legacy network and application architectures, such as IBM's Customer Information Control System (CICS), that they are looking to link to the Web. CICS is IBM's customizable multipurpose transaction monitor.
Among the different Web-to-host offerings are IBM's tn3270 and tn5250 products, which allow SNA users on an IP net to retrieve data from a mainframe or AS/400, respectively. There are other tools for special types of access, such as Cisco's Transaction Connection software, which allows users to connect directly to DB2 and CICS applications and data on a mainframe through a Cisco router.
Some Web-to-host products require an intermediary software/hardware gateway, such as an AIX or Windows NT server, to translate between IP and SNA. Longden says these gateways typically need to be tweaked to address specific customer needs. For example, a gateway could initially provide access to CICS applications from a common browser interface, but the gateway could be adapted to allow different end users different views of the applications.
On CareFirst's network, the SNA-to-IP sessions are handled by a product called ScreenSurfer from Intelligent Environments, a Burlington, Mass., software company. ScreenSurfer sits on an NT server attached to the host, allowing PC users to access CICS applications via a browser while handling customer service calls.
Practice makes perfect One secret to success is "testing, testing and more testing," says Laurence Kung, senior network manager at MCI WorldCom. The carrier runs a variety of
Web-to-host applications that are accessible to 75,000 desktop users. For instance, one portion of the net contains a 4,000-seat customer service center, which uses a screen scraper application to retrieve CICS and DB2 data from mainframes and present that data via browsers.
When MCI WorldCom's Web-to-host system was put into place several years ago, it needed frequent testing and adjustment. For instance, the team tested to make sure every connection was redundant in case one crashed. The company also checked for problems such as broken fiber cables, bit error rates and varying delays, all the way up the SNA and IP stacks. With lab simulations, the team also tested for router CPU and memory performance, the time it took for an SNA session to be established and network failover capacity.
Keeping it simple
Network executives should also ask themselves whether they want a Web-to-host product that has to be installed on every client or just on the host or Web server.
For Robin Metzler, it's the latter. Metzler is an IS manager at KidsPeace, a Bethlehem, Pa., health care organization.
KidsPeace's nine-site, 200-seat network is running VT 420 sessions through a Hewlett-Packard 9000 Web Server, which acts as a gateway for a Digital OpenVMS Alphaserver. For simplicity's sake, KidsPeace went with Seattle, Wash. -- based WRQ's Enterview 1.1, which resides on the Web server and provides a single point of management. Users click on a hypertext link on the KidsPeace home page and the Web server launches the application to establish the session, Metzler says.
Because the WRQ software resides on the HP server, Metzler doesn't have to touch each client to distribute the application. "The neat thing for me is I can administer it from my own PC," Metzler says. "If a user wants to change colors on his screen, I click on a hyperlink and connect to [the Web server], and the next time he gets a blue screen instead of a red one."
Metzler says users should keep things simple by having a Web server expert on hand to offer guidance when installing a Web-to-host product. He notes there were some challenges, such as performing keyboard remapping from the original screens to the new ones. A little research on the products allowed KidsPeace to overcome that issue, he says.
One issue still being resolved is how to establish a firewall that will ensure that only appropriate remote site users get into the Web server.
This story, "Taking Web-to-host pointers from the pros" was originally published by Network World.