Front-End Processor (FEP) Communications
A Front-End Processor (FEP), typically an IBM `37xx` Communication Controller, is a specialized hardware device that offloads communication tasks from the mainframe's central processing unit (CPU). It manages network connections, data link protocols, and initial data processing for terminals and other network devices, acting as an intermediary between the mainframe and the network. FEP communications refer to the processes and protocols managed by this device to facilitate data exchange.
Key Characteristics
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- Dedicated Hardware: A standalone hardware unit (e.g., IBM
3745,3746) specifically designed for network communication processing, separate from the mainframe CPU. - Network Control Program (NCP): Operates under the control of
NCP, a specialized operating system loaded into the FEP, which defines network topology, devices, and communication parameters. - Protocol Handling: Manages various communication protocols such as
SNA(Systems Network Architecture),SDLC,BSC,X.25, and oftenTCP/IPviaNCP/EP(Emulation Program). - Mainframe CPU Offload: Significantly reduces the processing burden on the mainframe by handling low-level communication tasks like polling, error detection, data buffering, and session management.
- Channel-Attached or Network-Attached: Can be directly connected to the mainframe via a high-speed channel (
ESCON,FICON) or operate as a standalone network node in a distributed network. - Multiplexing Capabilities: Capable of managing numerous terminal connections and multiplexing multiple low-speed lines onto a single high-speed line for efficient data transmission.
- Dedicated Hardware: A standalone hardware unit (e.g., IBM
Use Cases
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- Terminal Network Management: Connecting and managing large networks of
3270terminals (or their emulators) toCICSorIMStransaction processing applications on the mainframe. - Remote Site Connectivity: Providing reliable and secure communication links for remote offices, branches, or distributed systems to access central mainframe applications and data.
- Protocol Conversion: Handling different communication protocols from various network devices and presenting a standardized interface (e.g.,
SNA) to the mainframe'sVTAM. - Network Security and Control: Implementing network access controls, managing session establishment, and enforcing communication policies for users accessing mainframe resources.
- Legacy Network Integration: Supporting older communication protocols and devices, allowing them to interact with modern mainframe applications without requiring direct mainframe support for every protocol.
- Terminal Network Management: Connecting and managing large networks of
Related Concepts
The FEP is a cornerstone of traditional mainframe networking, working in close conjunction with VTAM (Virtual Telecommunications Access Method) on the mainframe. VTAM manages the logical sessions, application interfaces, and overall network control, while the FEP, running NCP, handles the physical network connections, data link control, and routing of data. Together, VTAM and NCP form the backbone for SNA communications, enabling applications like CICS and IMS to interact seamlessly with distributed users and systems over a wide range of network topologies.
- Regular NCP Updates: Keep the
NCPcode current to leverage performance improvements, new features, and critical security fixes, ensuring optimal FEP operation. - Implement Redundancy: Deploy redundant FEPs and communication lines with
NCPXID-based failover mechanisms to ensure high availability and minimize downtime for critical network access. - Performance Monitoring: Continuously monitor FEP CPU utilization, buffer usage, line statistics, and
NCPtrace data to identify potential bottlenecks and optimize network performance. - Secure Configuration: Carefully configure
NCPdefinitions to restrict unauthorized access, implement appropriate security protocols, and protect sensitive network traffic. - Capacity Planning: Periodically review network traffic patterns and FEP resource utilization to proactively plan for upgrades or additional FEP capacity before performance degradation impacts users.