SM Path Database

It should be noted that there are typically a number of paths between any two CA and/or router ports in a subnet. During discovery (i.e., configuration), the SM determines the topology of the subnet, assigns LIDs to the subnet's ports, and programs the switch Forwarding Tables. The SM also builds a path database that defines all of the possible paths between every possible pair of CA and router ports.

When software later desires to set up communications between two QPs (for RC, UC, and UD) or EECs (for RD), it can interrogate the SM's database to determine the possible paths between the two ports that will be used. The possible paths are defined by the LID and/or GID specified for the two ports. The path database also contains the operational characteristics of each of the possible paths between the two ports.

For more information on the path database, refer to “PathRecord” on page 975.