This topic describes Virtual Telecommunications Access Method (VTAM®) concepts for a subarea and Advanced Peer-to-Peer Networking (APPN) environments. VTAM is an application program that is based on System Network Architecture (SNA). This topic includes:

• VTAM functions
• VTAM nodes
• Network accessible units
• Network control sessions
• User sessions
• How VTAM locates resources
• Route selection
• Addressing
• Controlling network data flow using pacing