Network | IBM AS/400 instruction

Note: SDLC supports traditional AS/400 communication protocols, such as APPC, but does not support TCP/IP.

X.25 network

X.25 is a Telecommunications Standardization Sector (ITU-T) recommendation that defines the physical level (physical layer), link level (data link layer), and packet level (network layer) of the OSI reference model. A X.25 network is an interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) that operates in the packet mode, which is connected to public data networks by dedicated circuits. X.25 networks use the connection-mode network service.

An AS/400 X.25 line can be connected through a packet-switching data network (PSDN) and an adjacent remote system by using either a nonswitched or switched physical line. A switched line connection is one that is established on demand between the AS/400 system and the X.25 network. On nonswitched line connections, the AS/400 system supports both switched virtual circuits (SVCs) and permanent virtual circuits (PVCs). Only SVCs are supported on switched physical lines.

One X.25 line supports one or more virtual circuits. Each virtual circuit can support one of the following:

vOne or more Systems Network Architecture (SNA) sessions that can include Advanced Program-to-Program communications (APPC), SNA upline facility , remote work stations, or finance communications

vOne connection to an asynchronous communications host system (the primary or controlling computer in a communications network)

vOne connection to an asynchronous device through the X.25 network packet assembler/disassembler (PAD) function

vOne connection to an asynchronous communications host system through AS/400 PAD emulation

vOne user-defined communications facility

vOne Transmission Control Protocol/Internet Protocol (TCP/IP) link to an adjacent IP node or gateway. (A gateway is a device that is used to connect two systems that use two different communications protocols)

X.21 network

In data communications, a specification of the International Telegraph and Telephone Consultative Committee (CCITT) that defines the connection of data terminal equipment to an X.21 (public data) network.

The AS/400 system supports short—hold mode (SHM) operation for use with X.21 circuit—switched networks. X.21 short—hold mode is characterized by a series of connections and disconnections with a remote controller or system on an X.21 circuit—switched line. When there is no data traffic, the connection is broken, but the SNA sessions remain active. When either side has data to send, the connection is established again.

Chapter 10. Common networking standards 95

AS/400 specifications

The IBM AS/400, now known as the IBM iSeries, is a midrange computer system that has been a cornerstone of enterprise computing since its introduction in 1988. Designed to provide a robust platform for business applications, the AS/400 is celebrated for its reliability, scalability, and integrated database capabilities.

One of the key features of the AS/400 is its Integrated Operating Environment, which blends hardware and software resources seamlessly. This integration allows businesses to execute diverse workloads, ranging from traditional applications to modern web-based services, all on a single platform. The operating system, OS/400 (now IBM i), offers a rich set of APIs and tools for developers, simplifying application development and management.

Another standout characteristic of the AS/400 is its built-in database, DB2 for i. This powerful relational database management system allows for efficient data handling and provides advanced features such as support for SQL, XML, and JSON, making it easier for businesses to manage their data and integrate it with other systems. The database's tight integration with the operating system enables high performance and security.

In terms of scalability, the AS/400 can accommodate small businesses as well as large enterprises, with the ability to support hundreds of users simultaneously. Its architecture allows for easy upgrades in hardware, meaning that organizations can scale their systems without replacing the entire infrastructure.

Security is another critical attribute of the AS/400. With a sophisticated security model, it offers built-in user authentication, access control, encryption, and auditing capabilities to protect data and applications from unauthorized access.

The AS/400 also supports multiple programming languages, including RPG, COBOL, Java, and PHP, giving organizations the flexibility to choose the development tools that best fit their needs. This diversity helps maintain legacy applications while also developing new ones that leverage modern technologies.

Moreover, the platform supports both traditional green-screen interfaces and modern graphical user interfaces, allowing organizations to transition smoothly into contemporary user experience paradigms.

Overall, the IBM AS/400 stands out as a resilient, flexible, and secure computing platform that enables organizations to effectively manage their business operations, streamline processes, and adapt to changing market demands. Its unique combination of integrated features and capabilities ensures that it remains relevant in today's fast-paced technology landscape.