SNA Networking Protocols

System Network Architecture (SNA) by IBM is a suite of protocols mainly used with IBM mainframe and AS/400 computers.

• APPC - Advanced Peer-to-Peer Communications provides peer to peer services at the transport and session layer. Part of the System Network Architecture (SNA) suite of protocols.
• APPN - Advanced Peer-to-Peer Networking supports the computer connections at the network and transport layers. Part of the System Network Architecture (SNA) suite of protocols. 

http://www.comptechdoc.org/independent/networking/protocol/protsna.html