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SNA

   Also found in: Medical, Acronyms, Wikipedia, Hutchinson 0.02 sec.
SNA
(Systems Network Architecture) IBM's mainframe network standards introduced in 1974. Originally a centralized architecture with a host computer controlling many terminals, enhancements, such as APPN and APPC (LU 6.2), adapted SNA to modern peer-to-peer communications and distributed computing environments. SNA has mostly been replaced with TCP/IP as the world has migrated to the IP protocol. Following are some of SNA's basic concepts.

Nodes and Data Links
In SNA, nodes are end points or junctions, and data links are the pathways between them. Data links include high-speed local channels, the SDLC data link protocol, Token Ring and Ethernet.

Nodes are defined as Type 5 (hosts), Type 4 (communications controllers) and Type 2 (peripheral; terminals, PCs and midrange computers). Type 2.0 nodes communicate only with the host, and Type 2.1 nodes communicate with other 2.1 nodes (peer-to-peer) without going to the host.

SSCPs, PUs and LUs
The heart of a mainframe-based SNA network is the SSCP (System Services Control Point) software that resides in the host. It manages all resources in its domain.

Within all nodes of an SNA network, except for Type 2.1, there is PU (Physical Unit) software that manages node resources, such as data links, and controls the transmission of network management information. In Node Type 2.1, Control Point software performs these functions.

In order to communicate user data, a session path is created between two end points, or LUs (Logical Units). When a session takes place, an LU-LU session is established between an LU in the host (CICS, TSO, user application, etc.) and an LU in the terminal controller or PC.

An LU 6.2 session provides peer-to-peer communication and lets either side initiate the session.

VTAM and NCP
VTAM (Virtual Telecommunications Access Method) resides in the host and contains the SSCP, the PU for the host, and establishes the LU sessions within the host.

NCP (Network Control Program) resides in the communications controller (front end processor) and manages the routing and data link protocols.

SNA Layers
SNA is implemented in functional layers starting with the application that triggers the communications down to the bottom layers which transmit packets from station to station. This layering is called a "protocol stack." The SNA stack is compared with the OSI model below. Although SNA had major influence on the OSI model, there are differences in implementation.


SNA - Systems Network Architecture


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These firms can benefit greatly by SNA and viral marketing and are well-placed by their technology to use them and can do so by tracking customers' calling/contacting patterns have a fair idea of their networks and who may be the leaders.
Organizations can realize huge savings by migrating SNA applications to IP using TN3270 and TN5250, eliminating the need for older, cost intensive SNA communication hardware and software IBM?
Founded as a for-profit corporation in 2002 by a small group of disability and elder law attorneys serving the planning needs of individuals with special needs, the SNA now boasts a membership of more than 100 attorneys in 47 states.
 
 
 
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