A set of IBM mainframe networking standards and protocols introduced in 1974. Systems Network Architecture (SNA) originally defined a centralized architecture with mainframe hosts controlling terminals, but it has also been adapted for peer-to-peer communication and distributed client/server computing environments.
SNA includes services for configuring and managing system resources within an IBM mainframe networking environment.
SNA has seven protocol layers and is similar but not identical to the Open Systems Interconnection (OSI) reference model, whose development it influenced. The SNA protocol suite includes the following:
Before data can be transferred over SNA, a session must be established between an LU on the client and an LU on the host. For example, a Microsoft Windows NT–based or Windows 2000–based server running Microsoft SNA Server can connect to a mainframe host by using SNA. SNA Server provides connectivity between Windows and SNA environments by providing an SNA gateway running on a Windows NT–based or Windows 2000–based server. Windows clients can then connect to the SNA mainframe host by going through the SNA Server gateway.
By using LU 6.2, which is a peer-to-peer protocol, the Windows NT–based server running SNA Server or the mainframe host can initiate the user session. Clients on a Windows NT–based or Windows 2000–based network can then access data stored on the host, including data stored in structured or unstructured AS/400 or Virtual Storage Access Method (VSAM) files, DB2 database tables, and transaction processing monitors.
Non-SNA architectures such as Token Ring networks can interface with SNA networks using Service Points (SPs).