PU 2.1

Physical Unit type 2.1

A Systems Network Architecture (SNA) network node used to connect peer nodes in a peer-oriented network. PU 2.1 sessions do not require that one node reside on virtual telecommunications access method (VTAM). Advanced Peer-to-Peer Networking (APPN) is based upon PU 2.1 nodes, which can also be connected to a traditional hierarchical SNA network.