LU6.2 is a type of logical unit that supports communication between application programs in an SNA-based network.
LU6.2-compliant devices operate as peers within the network and can perform multiple simultaneous transactions over the network. LU6.2 devices can also detect and correct errors. The LU6.2 definition provides a common API for communicating with and controlling compliant devices.
SNA protocol that is the basis for revamping SNA's infrastructure. Device-independent, it provides facilities for peer-to-peer communications between two programs.
Logical Unit 6.2. An SNA protocol for communication between host processor and a device, or between processors. Used by CICS intersystem communications. APPC is the protocol used with LU6.2 architecture.
Basically to understand this protocol pls go thru SNA.Here is the best link: