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.
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