CINET - CICS Internet

Enhanced Definition

CINET, often referred to as CICS Internet, is a core component of CICS Transaction Server that enables CICS regions to act as both TCP/IP clients and servers. It provides the foundational infrastructure for CICS applications to communicate over TCP/IP networks, integrating CICS with the broader internet and enterprise IP networks. Its primary purpose is to facilitate network connectivity for CICS applications, supporting various internet protocols. CINET, or CICS Internet, is the component within CICS Transaction Server that provides TCP/IP connectivity for a CICS region. It enables CICS applications and services to communicate over TCP/IP networks, allowing CICS to act as both a client and a server for various internet protocols and services.

Key Characteristics

- TCP/IP Integration: Tightly integrated with the z/OS Communications Server TCP/IP stack, allowing CICS to leverage the full capabilities of z/OS networking.
- Protocol Support: Supports various TCP/IP protocols, including HTTP/HTTPS, raw TCP sockets, and can be extended for other application-level protocols.
- Resource Definitions: Requires specific CICS resource definitions like TCPIPSERVICE for inbound connections (listening ports) and URIMAP for mapping incoming URLs to CICS transactions or programs.
- Asynchronous Processing: Often utilizes asynchronous I/O operations to efficiently handle multiple network connections without blocking CICS tasks, improving throughput.
- Security Features: Leverages z/OS security mechanisms (e.g., RACF) and CICS security for authentication, authorization, and supports SSL/TLS for secure communication.
- CICS Web Support Foundation: Forms the underlying network layer for CICS Web Support (CWS), which provides high-level HTTP/HTTPS capabilities for CICS applications.

Use Cases

- Web Service Provider: CICS applications exposing business logic as web services (SOAP or RESTful) to distributed systems or external clients over HTTP/HTTPS.
- Web Service Consumer: CICS applications initiating requests to external web services or APIs to retrieve data or trigger actions in other systems.
- Custom Client/Server Applications: Developing bespoke TCP/IP client/server applications where CICS acts as a server or client using raw sockets for specialized data exchange.
- CICS Web Interface: Serving static or dynamic web content directly from CICS, allowing users to interact with CICS transactions via web browsers.
- Enterprise Application Integration (EAI): Facilitating real-time data exchange and transaction processing between CICS and other enterprise applications across different platforms using TCP/IP.

Related Concepts

CINET is fundamental to CICS Web Support (CWS), providing the underlying TCP/IP connectivity that CWS builds upon to handle HTTP and HTTPS requests. It directly interfaces with the z/OS Communications Server TCP/IP stack to manage network connections and data transfer. CINET's behavior is configured through CICS resource definitions such as TCPIPSERVICE and URIMAP, which dictate how incoming network requests are processed and routed to CICS transactions and programs. Security for CINET operations is often managed by RACF or other z/OS security managers, controlling access to network resources and CICS services.

Best Practices:

Secure Configuration: Always use SSL/TLS for sensitive data transmission by configuring TCPIPSERVICE resources with SSL(YES) or SSL(CLIENTAUTH).
Resource Definition Optimization: Carefully define TCPIPSERVICE and URIMAP resources, specifying appropriate PORT numbers, PROTOCOL types, and TRANSACTION IDs to ensure efficient routing and processing.
Performance Monitoring: Regularly monitor CINET activity using CICS statistics and monitoring tools (e.g., OMEGAMON, CICS Explorer) to identify bottlenecks and optimize TCP/IP buffer sizes and CICS task limits.
Robust Error Handling: Implement comprehensive error handling in CICS applications for network-related issues, including connection failures, timeouts, and invalid data, using HANDLE CONDITION or RESP codes.
High Availability: For mission-critical services, leverage z/OS Sysplex Distributor or CICSplex features to distribute incoming CINET traffic across multiple CICS regions, enhancing availability and scalability.