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  1. Introduction
  2. Network Model
  3. Topology
  4. Physical Media
  5. Wireless Media
  6. Network Card
  7. Modems
  8. Outside Connections
  9. Wide Area Network Connections
  10. Repeaters, Bridges, Routers
  11. Network Types
  12. Ethernet
  13. Token Ring
  14. ARCnet
  15. AppleTalk
  16. FDDI
  17. Architecture Comparisons
  18. Categories
  19. TCP/IP
  20. IPX/SPX
  21. NetBEUI
  22. AppleTalk
  23. SNA
  24. Others
  25. Suites and Network Layers
  26. Installing Drivers
  27. DNS
  28. Network Operating Systems
  29. Applications, mail, groupware, DBMS
  30. Backing up the network
  31. Troubleshooting
  32. Web, SNMP, admin, firewalls
  33. Networking Terms and Definitions
  34. Credits

System Network Architecture (SNA)

System Network Architecture (SNA) by IBM is a suite of protocols mainly used with IBM mainframe and AS/400 computers. Two SNA protocols are:

  • APPC - Advanced Peer-to-Peer Communications provides peer to peer services at the transport and session layer.
  • APPN - Advanced Peer-to-Peer Networking supports the computer connections at the network and transport layers.

Microsoft produced the SNA Server so PC networks could connect with SNA networks.

SNA Layers

SNA has its own network model which is:

  • Physical
  • Data link - Uses protocols such as token-ring or Synchronous Data Link Control (SDLC).
  • Path Control - Performs routing, division, and re-assembly of data packets.
  • Transmission - Connection software
  • Data flow - Prevents data overflows by monitoring and handling traffic
  • Presentation - Handles interfaces to applications
  • Transaction - Provides an interface for applications to use network services

SNA Network Devices

  • host systems
  • terminals
  • Output devices
  • Communications controllers
  • Cluster controllers - Allow many devices to connect through them. They connect ot a host or communications controller.

SNA Network Categories

  • Nodes
    • Type 2 - PCs, terminals and printers
    • Type 4 - Communications controllers
    • type 5 - Host computers used to manage the network
  • Data links - Connection between combinations of hosts, cluster controllers, or nodes.

Possible SNA communications architectures

  • SDLS - Synchronous Data Link Control
  • BSC - Binary Synchronous Communication sends bits in frames which are timed sequences of data.
  • Token-ring
  • X.25
  • Ethernet
  • FDDI

SNA units

NAU - Network Addressable Units

  • LU - Logical Units are ports that users use to access network resources
    • Type 1 - An interactive batch session
    • Type 2 - An IBM 3270 terminal
    • Type 3 - An IBM 3270 printer
    • Type 6.2 - A program to program session
    • Type 7 - An IBM 5250 family session
  • PU - Physical Units are a network device used to communicate with hosts.
    • Type 2 - Cluster controllers
    • Type 3 - Front end process
    • Type 5 - Host communications software

SNA software components

  • SSCP - Systems Services Control Point manages all resources in the host's domain.
  • NCP - Network Control Program performs routing, session management tasks. It runs in the communications controller.