What is High-Performance Routing?

High-Performance Routing is a set of enhancements for APPN that meets the following requirements:

Improved APPN data routing: HPR transports data at very high speeds by using low-level intermediate routing and by minimizing the number of flows over the links for error recovery and flow control protocols. The flows are minimized by performing these functions at the endpoints rather than at each hop (link) along the path.
Improved APPN reliability: HPR switches paths within the HPR portion of the network to bypass link and node failures if an acceptable alternate path is available. This occurs transparently to the sessions; in other words, the session is not disrupted.
Functional equivalence: HPR maintains functional equivalence with APPN. To do so, HPR continues to support priority routing, connection networks and multiple network connectivity. Priority routing allows the capability for higher priority traffic to pass lower-priority traffic in intermediate nodes within the HPR portions of the network. HPR also routes across connection networks or subnetwork boundaries in much the same way as APPN.
HPR routes are not given preferential treatment by the APPN routing algorithm. Existing non-HPR APPN routes will also be used if they meet the requirements of the APPN Class of Service.
Seamless migration: HPR is designed for drop-in migration. A given APPN node can be upgraded to the HPR level of function without taking down the network, without configuring new parameters at its adjacent nodes, and without any logistical complications or coordination.