Routing and flow control in Systems Network Architecture

Networks with multiple, interconnected nodes have imposed specific routing and flow control requirements on SNA. Such networks also provide the opportunity to use multiple active routes. The routing architecture of SNA employs the concepts of physical paths (explicit routes) and logical connections (virtual routes) to exploit this opportunity. Network congestion is reduced by local and global flow control mechanisms. An end-to-end VR pacing is used to provide global flow control; the window size is changed to adapt to network traffic and available buffer space.