Legacy SNA (1)
mainframe running Advanced Communication Facility/ Virtual Telecommunication Access Method (ACF/VTAM) servers as a hub of an SNA network; ACF/VTAM responsible for establishing sessions and distribution of recourses
SNA 7-layer model maps closely to OSI RM. The SNA and OSI layers are not identical and may not be inter-operable unless some form of gateway is provided.
- Physical - SNA does not define this layer (runs over Ethernet, FDDI, FR, X.25)
- Data Link Control - defines several IBM protocols including SDLC (Synchronous DLC), Token Ring Network, X.25
- Path Control - performs routing, and segmentation and re-assembly (SAR)
- Transmission Control - provides reliable end-to-end connection; encryption
- Data Flow Control - manages request and response processing
- Presentation services - coordinates resource sharing, converts data formats
- Transaction services - provide application services (management and distributed processing)