Overview of IBM Networking
DSPU and SNA Service Point
Figure 105 Router Acting as a DSPU Concentrator
LU
LU
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| PU 2 + 3 LUs | |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Token | RSRB |
|
|
| Token |
|
|
|
|
|
| |||||
|
|
|
|
|
|
|
|
|
|
|
| ||||||||
|
|
|
|
|
|
|
|
|
|
| |||||||||
|
|
| Ring |
|
|
| Ring |
|
|
|
|
| |||||||
|
|
|
|
|
|
|
|
| |||||||||||
|
|
|
|
|
| PU 2 | PU 5 |
|
|
|
|
|
|
|
|
|
| PU 2 + 1 LU | |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||
Mainframe |
|
|
| DSPU concentrator |
|
|
|
|
|
|
|
| |||||||
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||
|
|
| supporting 4 PUs |
|
|
|
|
|
|
|
|
|
| ||||||
with 1 PU and |
|
|
|
|
|
|
|
|
|
|
|
|
| ||||||
|
|
| and 8 LUs |
|
|
|
|
|
|
|
|
|
| ||||||
8 LUs defined |
|
|
|
|
|
| PU 2 + 2 LUs | S3223 | |||||||||||
|
|
|
|
|
|
|
|
| |||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Typically, a router establishes one or more upstream connections with one or more hosts and many downstream connections with PU type 2 devices. From an SNA perspective, the router appears as a PU type 2 device to the upstream host and assumes the role of a system services control point (SSCP) appearing as a PU type 5 device to its downstream PUs.
The SSCP sessions established between the router and its upstream host are completely independent of the SSCP sessions established between the router and its downstream PUs. SNA traffic is routed at a logical unit (LU) level using a routing algorithm that maps downstream LUs onto upstream LUs.
Figure 106 illustrates the SNA perspective of DSPU.
Figure 106 SNA Perspective of DSPU
Upstream PU
(PU type 2)
LU routing algorithm
Downstream PU A
(PU type 5)
Downstream PU B
(PU type 5)
S3224
Cisco IOS Bridging and IBM Networking Configuration Guide
