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Establishing Sessions with the Remote System

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Remote system session establishment is slightly different for a type 2.0 (T2.0) node than for a type 2.1 (T2.1) node. Session establishment for each node type is explained below, and examples of session establishment activities between the HP e3000 and the IBM remote system are shown later in this chapter.

NOTE: When configuring a data communications subsystem on the HP e3000, the node manager can choose to display link, node, and session activation and termination status messages on the system console. SNA Transport will then display node activation, link activation, and session establishment messages as each activity is performed.

These messages are not shown in the session establishment and termination examples later in this chapter; however, you should be aware that SNA Transport will keep you informed of activity on the communications link if you configure this type of logging. More information about logging can be found in Chapter 5 "SNA Link Troubleshooting"

For a Type 2.0 Node

The System Services Control Point (SSCP) uses PU-SSCP sessions to control the PU in each node in its domain. Each PU, in turn, controls the resources of the node it resides in. These resources include the links which have been configured for the particular node. The SSCP transmits an ACTivate Physical Unit (ACTPU) command request to the PU to establish a session with the PU. When a PU-SSCP session is activated, the node that contains that PU becomes an active node in the SNA network. SNA Transport manages the PU-SSCP sessions of the HP e3000.

The SSCP uses LU-SSCP sessions to control dependent LUs and to establish dependent LU-LU sessions. The SSCP sends the command ACTivate Logical Unit (ACTLU) to establish LU-SSCP sessions. SNA Transport manages LU-SSCP sessions on the HP e3000.

A dependent LU-LU session enables data to be exchanged between two end users, between an end user and an application running on the host processor (such as TSO), or between a job and the Job Entry Subsystem (for example, JES2) running on the host. The LU-LU session can be thought of as a temporary logical connection that allows two LUs to exchange data.

LUs on the HP e3000 communicate with the SSCP to establish dependent LU-LU sessions. A dependent LU sends a session initiation request to the SSCP via its LU-SSCP session. The SNA services manage the LU-LU sessions on the HP e3000.

For a Type 2.1 Node

Session establishment for a T2.1 node is different than establishment for a T2.0 node in one major way: An independent LU on a T2.1 node can establish an LU-LU session with a remote system LU without the need for a corresponding LU-SSCP session. This is possible because an independent LU sends a BIND request directly to a remote system LU to establish an independent LU-LU session. The BIND is routed through the network to the remote system LU by using the remote system LU's name and node name.

NOTE: At this time, LU 6.2 API/XL is the only SNA service that makes use of the T2.1 node capabilities.



Chapter 4 SNA Node Startup and Shutdown

Establishing PU-SSCP Sessions on the HP e3000