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Table Of Contents
About this Guide
This document describes how you can use the Cisco Channel Interface Processor (CIP) and the Channel Port Adapter (CPA) in conjunction with the Telnet 3270 (TN3270) Server feature of the Cisco IOS software to:•
Address requirements for accessing mainframe applications while moving to IP networks
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The document provides an overview of TN3270, describes how to configure and manage the TN3270 Server, and provides migration scenarios.
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Intended Audience
This document is for anyone who wants to learn more about Cisco's data center solutions. It begins with an overview that is appropriate for all audiences. It also includes design guidelines and sample configurations appropriate for network designers, systems engineers, consulting engineers, and network support personnel. The document assumes familiarity with networking and Cisco routers, but does not assume mastery of either.Examples of key configuration commands are shown to aid in understanding a particular configuration. However, this document does not contain the exact and complete configurations. This information is available and regularly updated in Cisco Connection Online (CCO) and in the Cisco product documentation. CCO is Cisco's primary, real-time support system and is accessible at the World Wide Web address http://www.cisco.com.
Document Structure
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Cisco's Data Center Solutions
For the last 20 years, businesses have depended on mainframe applications. A trillion dollars have been spent on mainframe applications, and those applications will not disappear tomorrow. In addition, a great deal of development effort has been invested in mainframe security, backup, and redundancy, making the mainframe an excellent server for the networks of tomorrow. For these reasons and others, mainframes will continue to play a major role in networks for years to come. This reference guide describes how to use Cisco solutions to tightly integrate your mainframes with the rest of your network as it evolves to support higher bandwidth and Internet and intranet access.Evolution of the Data Center
In the early 1970s, computing cycles and memory were very expensive. Most enterprises centralized their computing cycles in large mainframe computers. These mainframe computers resided in a data center—often called a "glass house." End users accessed mainframe applications from teletype machines or display terminals (known as 3270 devices). IBM developed Systems Network Architecture (SNA) to define how display terminals could access applications and information in IBM mainframes. shows a simple SNA network and some of the key components.Figure i Sample SNA Network
Today, because computing cycles are so inexpensive, most desktop computers have more processing power than the mainframes of the 1970s. Processing power is spread throughout enterprises and is found not only on the desktop, but also in powerful workgroup computers. IBM mainframes are still used to support SNA applications, but access to those applications can be from 3270 display terminals, PCs running 3270 emulation programs, PCs running more advanced SNA protocols, or TCP/IP end systems that use the TN3270 protocol. IBM mainframes are used for more than just SNA applications. More than 40 percent of the mainframes worldwide also run TCP/IP, and that number is expected to grow to 85 percent by the year 2000. shows the four paradigms of IBM mainframe access.
Figure ii Evolution of IBM Networks
Today, many IBM networks still access SNA applications in the mainframe from SNA clients (Figure ii, quadrant A). However, more than 40 percent of organizations have migrated their backbone to TCP/IP (Figure ii, quadrant B). From a data center perspective, these two scenarios are the same. These scenarios are presented in the SNA Internetworking Design and Implementation Guide, which is volume 3 in Cisco's IBM Internetworking Design Guide Series. (This document was formerly called the Data Center Design and Implementation Guide.)
With the proliferation of Internet connections and because TCP/IP is included free with Windows, more organizations are looking at TN3270 as a low-cost way to access their SNA applications. TN3270 eliminates the requirement for dual stacks on the desktop and minimizes the cost of specialized desktop software.
Another alternative, provided by the OC://WebConnect Pro family, is to use a specialized Web server to download Java applets to clients. The Java applet provides access to a typical 3270-like interface or, optionally, a Web-browser interface. No specialized software is required at the desktop, and the Web server automatically downloads the most current Java applet, eliminating the cost of purchasing and maintaining specialized desktop software. Web browsers offer an intuitive interface that is well understood by customers, suppliers, and employees. The Web server maintains a permanent and secure TN3270 connection to either a TN3270 server in a Cisco router or a TN3270 server running in an IBM mainframe.
SNA is isolated to the data center, and the desktop has TCP/IP only. This scenario (Figure ii, quadrant C), is covered in this document.
Finally, some environments are either building new mainframe applications using TCP/IP or rewriting existing applications to use TCP/IP. This scenario (Figure ii, quadrant D) is covered in IP for Mainframes Design and Implementation Guide, which is volume 5 in Cisco's IBM Internetworking Design Guide Series.
Credits
Many people have contributed to this document. The technical owner, Craig Brown, wishes to thank the following people for their contributions:Jon Beck
Michael Boe
Derek Bolton
Lori Bush
Kurt Iriart
David Katz
Donna Kidder
Volker Schuster
Herbert Szumovski
Cisco Connection Online
Cisco Connection Online (CCO) is Cisco Systems' primary, real-time support channel. Maintenance customers and partners can self-register on CCO to obtain additional information and services.Available 24 hours a day, 7 days a week, CCO provides a wealth of standard and value-added services to Cisco's customers and business partners. CCO services include product information, product documentation, software updates, release notes, technical tips, the Bug Navigator, configuration notes, brochures, descriptions of service offerings, and download access to public and authorized files.
CCO serves a wide variety of users through two interfaces that are updated and enhanced simultaneously: a character-based version and a multimedia version that resides on the World Wide Web. The character-based CCO supports Zmodem, Kermit, Xmodem, FTP, and Internet e-mail, and it is excellent for quick access to information over lower bandwidths. The Web version of CCO provides richly formatted documents with photographs, figures, graphics, and video, as well as hyperlinks to related information.
You can access CCO in the following ways:
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For a copy of CCO's Frequently Asked Questions (FAQ), contact cco-help@cisco.com. For additional information, contact cco-team@cisco.com.
If you are a network administrator and need personal technical assistance with a Cisco product that is under warranty or covered by a maintenance contract, contact Cisco's Technical Assistance Center (TAC) at 800 553-2447, 408 526-7209, or tac@cisco.com. To obtain general information about Cisco Systems, Cisco products, or upgrades, see www.cisco.com/warp/public/687/cust_service/contacts.shtml.
