There is a prevailing trend within many enterprise networks – the integration of two dominant network protocols and infrastructure, SNA and TCP/IP. Cisco Systems has helped thousands of enterprise organizations worldwide integrate SNA with IP. As the market leader in SNA/IP integration solutions, Cisco has a breadth of products to assist organizations of any size to create end-to-end business solutions.
The industry trend of client server development for e-commerce, business intelligence and transaction processing has led to a demand for direct access from LAN-based clients and servers to host resident operational data. This has resulted in a proliferation of gateways systems running on UNIX, Windows NT and OS/2 systems being used to handle connections to host data. To meet the challenges facing these enterprises, and in response to problems associated with proprietary gateways, Cisco offers the standards-based, Cisco Transaction Connection (CTRC) as an alternative.
The goal of this document is to provide a comprehensive understanding of the benefits of using CTRC as the foundation for integrating System 390 compatible hosts in client server development. The benefits of using CTRC include:
- High performance
- Improved manageability
- Scalability
- Lower cost of ownership
This document is written for network managers, application developers, database administrators and management personnel responsible for integrating System 390 compatible hosts with client server development. It provides an overview of the technology and an analysis of the technical benefits.
Trends in Enterprise Application Development
IT organizations are implementing new applications for e-commerce, business intelligence and basic transaction processing. The advent of the World Wide Web (WWW) is a driving force for these trends in application development. Therefore, the need to deliver useful information from reams of raw data is driving the development of a new generation of business intelligence applications. Point and click interfaces provide intuitive, easy-to-use systems improving productivity. These applications represent the largest IT growth area and are similar in their basic requirements for direct data access.
- E-Commerce
- Publishing
- Decision Support
- Data Mining
- Data Warehousing
- Data Marts
- Client-Server with Visual Basic, C++, Delphi or PowerBuilder
Industry studies show over ninety percent of mainframe enterprises will implement applications requiring a direct connection from applications running in the LAN to operational data on the host. The challenge is how to most effectively connect these new class of applications to host-based, operational data.
IBM Network Evolution
When considering client server development that integrates host systems it is imperative to understand the network challenges inherent in such an undertaking. Original host-based network requirements were based on a single network protocol, System Network Architecture (SNA). These networks connected SNA users (using native SNA stacks or emulators) to mainframes or AS/400s in the data centers. Today, the TCP/IP network protocol is becoming a dominant presence and the challenge to integrate SNA and TCP/IP is paramount.
Cisco Systems has drawn upon its experience helping hundreds of large organizations worldwide integrate these environments. The four-phase model below illustrates a typical migration path. This model helps to describe some common phases in network integration. Some organizations find that their network is completely represented by one of the phases, while others realize that they have two or more of the phases implemented in various sectors of their network. The phases can be differentiated by the protocol that runs in each of three key elements in the network: the mainframe/midrange computer, the network backbone, and the desktop.
As LANs and PCs evolved, a requirement for multi-protocol traffic developed. With the availability of applications and equipment and the growing importance of the Internet, the choice of backbone protocol has become TCP/IP. While the implied progression in the graphic is network change, desktop changes and then application change, there are no fixed rules. In reality, many types of clients must coexist concurrently in the same network. For example, new users use TN3270, while existing users remain on emulators for some period of time. When providing direct access to host data from applications, the solution should consider the current state of the enterprise network and be flexible enough for future network evolution.
How Applications Access the Host
Cisco Transaction Connection provides connections to CICS and DB2 from applications using standard network protocols. Understanding how applications access DB2 and CICS from remote sources is helpful to understanding the CTRC product. Access protocols are generally categorized by Application Program Interfaces (API) used by applications, data stream or data access architectures that travel across the network and the host-based applications that provide access to data. This section defines the components that make up the end-to-end solution related to the host, the client and the network.
On the Host
CTRC allows applications to access CICS and DB2 on the host.
- Customer Information Control System (CICS) – CICS is IBM's industry leading Transaction Processing Monitor. It is used by 490 of the top 500 companies listed by Fortune magazine and across all industries and most countries in the world.
- DB2 – IBM’s RDBMS, DB2 is a leader in performance and market share, with more than one million user licenses worldwide. DB2 offers open, industrial-strength database management for e-business, business intelligence, transaction processing and a broad range of applications.
On the Client
Applications that access host resources use several common APIs. In some cases the APIs are so well defined that products from third party vendors are widely available that work across all RDBMS implementations. In other cases, the only way to utilize the APIs is to actually write applications that utilize them for specific purposes. The APIs are supplied through drivers and programming libraries from a number of vendors and are commonly referred to as data access middleware. The following is a list of APIs commonly used to access DB2 and CICS on the host.
- Extended Call Interface (ECI) – The ECI provides a programmable interface for invoking CICS server based applications that are written as callable services. ECI calls may be synchronous (i.e., blocking) or asynchronous (i.e., non-blocking with a callback), permitting concurrent requests. Each ECI request specifies security information (userid and password) and is managed as a unique request to a CICS server. CICS returns a response to the call by passing back an unstructured memory segment known as the COMAREA. The application is responsible for interpreting the returned data.
- Extended Presentation Interface (EPI) – The EPI provides a programmable interface to 3270 terminal oriented CICS applications, with separate calls for Signon specifying security information, data stream flows, and Signoff. No changes to existing 3270-based host applications are required. The EPI enables the user interface to be upgraded by adding a GUI front-end to these existing 3270-based CICS applications.
- Open Database Connectivity (ODBC) – ODBC is a defacto standard designed by Microsoft to promote interoperability between Windows applications and any RDBMS. Over 200 application products have implemented ODBC support. ODBC provides an API supported by most application development languages available for Windows.
- SQL Call Level Interface (CLI) – CLI is The Open Group standard API for RDBMS access. It is most popular on UNIX platforms, which do not have support for ODBC.
In the Network
The client APIs convert requests into the appropriate data access format to be interpreted on the host. There are two primary protocols, one for accessing DB2, the other CICS.
- Inter Systems Communication (ISC) – ISC is a protocol for inter-operability with CICS applications and their results over cross-domain host boundaries or over a network from remote systems. Current implementations on host systems support connections via LU6.2 and ANYNET.
- Distributed Relational Database Architecture (DRDA) – DRDA is a protocol for sending SQL commands and their results through a network. Until 1996, DRDA was designed to work only over SNA connections. With Release 5.1 of DB2 DRDA now works over TCP/IP connections. All IBM DB2 systems support DRDA. The Open Group adopted DRDA as the interoperability standard among RDBMS in October 1998.
CTRC Overview
Cisco Transaction Connection is a feature of the Cisco IOSâ software designed to carry ISC and DRDA traffic across the network.CTRC converts ISC and DRDA requests flowing over TCP/IP to corresponding SNA requests, which are sent to the mainframe for processing. When results are returned, the process is reversed.
Application Component
At the workstation, a client application issues a command using a middleware product. To access DB2, an ODBC-enabled driver such as StarQuest’s StarSQL Enterprise Edition or IBM’s DB2 Connect would be required. IBM’s Common Client provides an interface to connect to CICS. The middleware converts whatever API is being used to ISC or DB2 for connections to CICS or DB2 respectively. The ISC or DRDA message is packaged into a TCP/IP message and then sent to the router.
Router Component
A Cisco router that is running CTRC receives the TCP/IP packet. It establishes an SNA session between CTRC and CICS or DB2, sets up a connection between the TCP/IP network address and the LU-LU session (similar to TN3270), then converts the message to SNA, and sends the SNA message to CICS or DB2. At this point the TCP/IP port is "linked" to the SNA session and does not employ encapsulation methodologies, like ANYNET. CICS or DB2 builds the reply and works with VTAM to format it. Within the router, the CTRC component receives the SNA packet, extracts the reply, and builds a TCP/IP message. The TCP/IP message is sent to the end user, where the DRDA or ISC message is passed over to the API and the originating application.
Inside the Router
CTRC essentially replaces an incoming IP message header with a corresponding SNA message header and routes the message to the host using an SNA session. Outgoing SNA message headers are, likewise, replaced by corresponding IP message headers. The process is optimized by the use of direct memory access (DMA) so that messages are received in and sent from the same data buffer.
In contrast, other solutions use general-purpose operating systems like UNIX, Windows NT or OS2 to service connections. Data must be copied in and out of the kernel from one process to another. The result is two context switches requiring four data copies to and from the processes and the kernel. Each process does work on the data before sending it on. The entire set of procedures is executed for sends and receives. This doubles the overhead for each completed request and substantially reduces throughput and scalability.
Network Design Options
As a part of the Cisco IOS software, Cisco Transaction Connection can be placed where it is most appropriate in the customer network. CTRC can reside with the Channel Interface Processor (CIP) in a single router, or as a separate router in the data center. If the network has not been converted to TCP/IP, Cisco Transaction Connection can be placed in a remote router, converting TCP/IP messages to SNA to send them across an SNA backbone. Because CTRC is part of the Cisco IOS software, CTRC can take advantage of the many network services provided within the router. For example, in conjunction with security software on the database host, Cisco can provide end-to-end security to meet business requirements. In a total network design, use of Cisco's LocalDirector along with Cisco Transaction Connection will provide a means to distribute the load, and allow for automatic recovery from failures. The choice depends on network size and functionality positioning.
CTRC can be placed on channel attached routers directly connected to host systems. This is a simple high volume configuration that provides excellent performance characteristics. CTRC is compatible with other Cisco SNA/IP integration products (like TN3270 Server) allowing router resources to be shared.
Cost Savings
General purpose gateway solutions have limitations associated with their platforms, limited connectivity options, incremental support problems and high maintenance costs. CTRC reduces the management costs associated by providing a reliable, low maintenance router platform, that can scale to 5000 concurrent connections. (Many gateway solutions can only provide hundreds of such connections.) This consolidated gateway approach simplifies the network architecture by removing some of the additional devices in the network, and enables enterprises to realize significant cost savings, both initially as well as during production use of the solution.
Conclusion
Today’s enterprise environment requires connectivity between application servers, transaction processors and host resident operational data over the network. Each component is well suited to its role in the IT scheme. Problems arise when functionality is placed in an area that it is not particularly well suited. A proliferation of servers, whose primary function is that of providers of network services, threatens to undermine the benefits of multi-tiered architecture. CTRC solves this problem by placing the fundamental service of connectivity into network.
By residing on Cisco router hardware as a feature of Cisco IOS, CTRC enjoys performance and configuration benefits unmatched by generalized computers systems acting as gateways.
The net result of implementing CTRC includes:
- High performance
- True enterprise scalability
- Ease of configuration
- Compatibility with existing application environments
- Low cost of ownership
- Ease of management
Most enterprises recognize the value of incorporating the Internet into their business strategies, whether it is used to improve internal connectivity to their own remote users or to open applications to new users. Building the corporate Intranet means developing a TCP/IP infrastructure that supports this capability today. The ability to introduce TCP/IP end users without requiring application and database changes is a key step in enabling the corporate Intranet.
Cisco Transaction Connection technology complements Cisco’s existing product line and provides high-performance database access across networks—an end-to-end solution for connecting desktops to data.
Copyright Ó 1999 Cisco Systems, Inc. All rights reserved. Cisco, Cisco IOS, Cisco Systems, and the Cisco Systems logo are registered trademarks of Cisco Systems, Inc. in the U.S. and certain other countries. All other trademarks mentioned in this document are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any of its resellers.
Ó 1999 StarQuest Software, Inc. All rights reserved. This document is for informational purposes only. All trademarks or registered trademarks may be the properties of their respective owners.
