A Method for Load Balancing across Parallel APPN Extended Intersubnetwork Boundaries
Original Publication Date: 1999-Nov-01
Included in the Prior Art Database: 2003-Jun-12
Problem Statement. Advanced Peer to Peer Networking (APPN) Extended Border Nodes (EBNs) as currently architected attempt to search for cross-subnet resources by using any available path(s). So, typically more than one search subprocedure exits the origin subnet if there are multiple exit points from the subnet. They also have the property that sessions are brought up across the intersubnet boundaries across which the search succeeded. Once a resource is found and its location is cached by the EBNs across the subnet boundaries, subsequent searches for that resource also traverse the same path. Because of this, subsequent sessions get setup across the same subnetwork boundaries. This can result in concentration of load on specific subnetwork boundary EBNs. This could be undesirable especially if this subnetwork boundary is known to be not the best available one. In a customer environment where multiple subnetwork boundaries have been defined and some sort of parallel connections are available for redundant connectivity, it is desirable to have a way of controlling which intersubnet boundary is used for setting up the sessions with which resources. The solution proposed in this disclosure addresses these problems, and under stable network conditions, guarantees deterministic search exit and session-setup through a user configured "preferred EBN", provisions configuring backup paths that will be used if there are failures in the preferred path, after recovery of preferred path from failure, the session-setup reverts back to across the preferred path automatically. The solution works by letting the customer select a "preferred exit EBN" for searching for a particular resource or a set of resources. This, the customer sets up by configuring the SRLs (Subnet Routing Lists) on each EBN in the subnet. Once the preferred exit EBNs are setup for the resources, the searches for those resources are made to exit the subnet via the preferred exit EBN. This in turn ensures that the sessions get setup across that boundary.