1. A computer program product for processing communications between a host processor and a plurality of devices connected to the host processor by an input/output processing system, comprising a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: receiving, by the host processor, physical configuration information including identification of a location of each physical endpoint connected to the host processor and a plurality of communication paths associated with each physical endpoint; sending at least one message to each physical endpoint on each of the plurality of communication paths in response to receiving the physical configuration information, the at least one message requesting identification of a logical entity at the endpoint, and receiving logical configuration information identifying the logical entity; generating a data collection accessible by the host processor, the data collection including the physical configuration information and the logical configuration information for each logical entity, and identification of the plurality of communication paths to each logical entity; comparing the data collection to pre-existing configuration data including a configuration of entities in the network and identifying new entities; and updating the pre-existing configuration data, wherein updating includes selecting device numbers and control unit numbers based on availability of the numbers in the existing configuration, and selecting the device numbers and control unit numbers based on a type of I/O device.