SNA functions. Logical units define a set of services and transmission capabilities that are
assigned users. SNA defines seven LU types: 0, 1, 2, 3, 4, 5, and 6.2. There are many LU types
because memory and processing on SNA devices is expensive. IBM decided to create several
types that allowed specific functions to be associated with the end user so that only the
minimum processing and memory would be required for a particular device.
1, and LU 3 are not considered test topics. We will discuss the two most important--LU 2 and
LU 6.2.
(APPC) and peer-to-peer communication between peripheral nodes.
activating and deactivating SNA resources and initiating and terminating LU sessions. An SNA
domain consists of all the resources managed by an SSCP. A domain usually has more than one
subarea. (Subareas are discussed in the following section.)
shutdown of the network. SSCP is required to activate a session between two logical units. A
session between two logical units is called a LU-LU session, which is how devices
communicate in an SNA network. In Figure 12-4, for the two FEPs to communicate in the SNA
domain CCDP, the SSCP must initiate and control the LU-LU session.