What is SNA System Network Architecture

Delving into SNA: System Network Architecture

Within the realm of enterprise networking, Systems Network Architecture (SNA) emerges as a historic and foundational protocol suite developed by IBM. While not as widely used today due to the rise of open standards like TCP/IP, understanding SNA provides valuable insight into the evolution of network communication and its influence on modern architectures.

The Origins of SNA (1974):

Introduced in 1974, SNA aimed to establish a standardized approach for communication among various IBM hardware and software components, including:

• Mainframe computers: These served as the central processing powerhouses within large organizations.
• Terminals: These were dedicated devices used for user interaction with the mainframe system.
• Peripheral devices: These included printers, storage units, and other equipment connected to the mainframe.

Core Principles of SNA:

SNA adheres to a layered communication model, similar to the OSI (Open Systems Interconnection) model. Key aspects of SNA include:

• Layered Architecture: SNA divides communication functions into distinct layers, each with specific responsibilities. This modular approach facilitates development and maintenance.
• Physical Unit (PU): This layer handles the physical transmission of data across communication lines.
• Data Link Control (DLC): This layer manages error detection and correction to ensure data integrity during transmission.
• Network Control (NC): This layer is responsible for routing data packets across the network and managing session establishment between communication points.
• Presentation Services (PS): This layer deals with data formatting and presentation, ensuring compatibility between different devices within the network.
• Session Services (SS): This layer establishes, manages, and terminates sessions between communicating entities.
• High-Level Protocols (HLPs): These protocols reside above the core SNA layers and provide specific application-oriented services like file transfer (FTAM) and database access (DB2).

Communication Flow in SNA:

Data transmission within an SNA network involves interactions between different types of nodes:

• Host (Mainframe): This acts as the central processing unit in the network, running SNA software and providing resources to other nodes.
• End User Devices: These include terminals, printers, and other user interfaces that interact with the host system.
• Communication Controllers (CCs): These specialized hardware devices manage data flow between the host and peripheral devices connected through dedicated communication lines.

Legacy vs. Modern Usage of SNA:

While the widespread use of SNA has diminished with the rise of TCP/IP and open standards, it's important to understand its ongoing influence:

• Legacy Systems Integration: Many organizations still maintain core business applications running on mainframes. SNA connectivity remains crucial for integrating these systems with newer network architectures.
• SNA emulation products: Software solutions exist that enable modern devices and applications to communicate with mainframes using SNA protocols.

Conclusion:

Systems Network Architecture (SNA) played a pivotal role in shaping the landscape of enterprise networking. Although its dominance has waned, understanding its layered approach, communication principles, and historical significance remains valuable for network engineers and IT professionals dealing with legacy systems or mainframe integration scenarios. As we move forward, SNA's influence can still be seen in the development of new communication protocols and network architectures.