NT-based Web-to-host products that will have your Web-client users singing your praises
[Editor's Note: This comparative review originally included test results for WRQ's Reflection for the Web 3.0. At press time, the vendor had released version 4.0, which contains significant changes to the reviewed product; version 3.0 is no longer available for purchase. For these reasons, Reflections for the Web 3.0 doesn't appear in this review. For information about Reflection for the Web 4.0, see WRQ's Web site at http://www.wrq.com/.]
Providing host-server access to your customers and offsite users is a great way to leverage your enterprise business' sizeable investments: IBM mainframe or AS/400 systems and the Web infrastructure that you use for intranet, extranet, and Internet functions. The Web-to-host products in this review provide remote and global Internet access to your IBM host systems—without requiring the hosts to have expensive dedicated communication links. The only required software on the client side is a standard Web browser. When you install Web-to-host software on a Web server, a user can download a Java applet or an ActiveX control to a Web-based client, then use that control to run host terminal emulation sessions from the client's Web browser. One product (Winsurf Mainframe Access 2.5) provides host access through on-the-fly HTML conversion in addition to using ActiveX controls. Figure 1 provides an overview of a typical Web-to-host implementation.
I tested eight Windows NT-based Web-to-host products. The basic review criteria were the products' ability to provide IBM mainframe 3270 terminal emulation, to provide IBM AS/400 5250 terminal emulation, and to directly locate host network resources without using Windows 2000 Active Directory (AD) or a Lightweight Directory Access Protocol (LDAP) server (Table 1, page 108, summarizes the products' features). The Web server I installed the products on was a 200MHz Pentium Pro processor system with 128MB of RAM, running Microsoft IIS 4.0. I used Microsoft Internet Explorer (IE) 5.0 and IE 4.0 on my client systems, and I ran the terminal emulation sessions across a 10MB Ethernet network segment.
A Host of Key Features
The Web-to-host products that I tested displayed definite differences in several key areas. These areas include the type of host connection, printer-emulation support, centralized management capabilities, terminal-emulation controls and display options, and security and data-stream-encryption support.
The host connection. Most of the Web-to-host products I reviewed fall into one of two camps: products that establish direct connections between clients and the host server, and products that channel connections through the Web server. Each method had trade-offs. The products that connect clients directly to the host typically rely upon the host server to provide monitoring and session-level security. This arrangement prevents the Web server from becoming a bottleneck but usually means that the Web-to-host software can't provide session-monitoring or security-management capabilities. Products that connect clients through the Web server typically provide centralized session monitoring and security, but the Web server also becomes a potential point of failure. Several products support both direct and gateway-style connections between the clients and the host; these products offer the best of both worlds.
Printer emulation. All the products provide 3270 and 5250 terminal emulation, but some products lack printer-emulation support, which lets users produce local printouts rather than depend on printers at the host-system location. Several products support 3270 printer emulation but don't support the enhanced TN5250 protocol, which is necessary for 5250 printer emulation.
Centralized management. Centralized configuration and session monitoring are important Web-to-host product management features. Centralized configuration lets you set up and configure from a common management location all client-to-host connections, thus vastly simplifying the deployment of multiple clients. The ability to set up and manage groups as well as individual users is another useful deployment feature. Centralized session monitoring can help you troubleshoot your system and track licensing from one management location. All the products that I reviewed provide centralized configuration. However, centralized monitoring is a different story: Some products let me monitor and record usage and generate management reports; other products provide no monitoring capabilities.
Terminal-emulation controls and display options. Most of the products I reviewed provide host-server connectivity through a Java applet that the client downloads; some products provide an ActiveX control or Web-server-based on-the-fly HTML conversion. (Several products provide multiple mechanisms.) Although all the products provide basic terminal emulation through a standard Web browser, some products also provide browserless host-server access through Java applications or standalone Windows-based applications.
The quality of the products' terminal emulation displays also differs. Some products provide only a standard 25-line character-based display, so I needed to scroll to see the entire screen. Other products provide a resizable display that let me see the entire screen within the browser; this type of display is easier to work with. Many of the products also support as many state-of-the-art display-emulation features as standalone host-emulation software provides. For example, some products provide full support for custom keyboard mapping and screen colors, as well as macro recording and custom programming interfaces.
Security and data-stream encryption. Security is always of paramount concern, especially when a connection takes place over the Internet. Standard 3270 and 5250 emulation products send clear-text streams between the client and the host server. This type of connection is acceptable for local network connections but is unacceptable across an Internet-based WAN link. The reviewed products that connect clients directly to the host server either provide no session security or else rely on host-based Secure Sockets Layer (SSL) support. The products that use gateway-style connections generally encrypt the data stream between the client and the Web server. Some of these products also encrypt the data stream between the Web server and the host server, but most of the products generally require the Web server/host server connection to occur over a secure network link. All the products that provide security do so through SSL; the products that provide data-stream encryption employ various encryption protocols. Almost every product lets you customize the TCP/IP ports that the client uses to connect to the host server so that you can easily change the default port in secure firewall-based installations.
Results
Of the products that I reviewed, my favorite is IBM's WebSphere Host On-Demand 4.0. The product is easy to configure and use, and it provides all the advanced display and printer emulation features that I expect from the maker of IBM mainframe and AS/400 systems. In addition, the product's unique Database On-Demand feature lets end users submit ad hoc databases. The product also provides excellent security, permitting encryption of both Web-to-host and Web-to-client sessions.
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