Abstract: A method for acquiring the node identifier of a node in a data processing input/output (I/O) system having a plurality of nodes. This procedure is part of the initialization of each node in the I/O system and may be used to establish the configuration of the I/O system such that if a connection breaks or a fault occurs between nodes, the configuration can be confirmed after the break or fault is corrected. This prevents data from being sent to the wrong device if lines were connected in a different configuration during the correction of a fault. The node identifier is a worldwide-unique identifier such that only one node is identified by a node identifier. The node identifier contains a validity code that specifies if the node identifier is valid. Also disclosed is a retry procedure for retrying the acquisition of a node identifier if the acquired node identifier is not valid, and a deferral procedure which defers the retry procedure if a link is not available.

Abstract: A fault isolation system for use in a network in which bit errors resulting in detected code violation errors or disparity errors may be propagated from a first link to a second link of a network in which multiple serially coupled links may couple two devices. Errors in excess of a first threshold are detected at the receiving end of the first link, while errors in excess of a second threshold greater than the first threshold are detected at the receiving end of the second link. Errors are attributed to the first link in response to the detection of errors in excess of the thresholds on both links and are attributed to the link for which the threshold was exceeded in response to the detection of errors in excess of the threshold on only one of the links. If a substantial number of the bit errors resulting in the threshold being exceeded on the second link originated on the first link, the first threshold will also be exceeded with a high degree of probability.

Abstract: The invention relates to methods and apparatus for isolating faults in link-connected systems utilizing fault reports generated from within the system itself. The reports are transmitted to a central location, preferably during a predetermined time period, and are used to create a single error message identifying the probable nature and location of the fault. A preferred embodiment of the invention does not require either the construction or maintenance of systemwide configuration tables, commonly used performing fault location and analysis. Instead, each unit of a pair of link coupled units, initially or on reconnection, interrogates a link adapter at the other end of the link for an identifier that identifies both the remote unit and the remote link adapter. This "nearest neighbor" information is stored locally at each unit, and is transmitted to the central location when an error is detected.