Case studies depicting ISDN network layer interoperability and standards nonconformance were evaluated, and categorized by type. In each case study the root cause of the interoperability problem was identified, and validated with reference to the applicable ISDN standard. Corrective measures were proposed, and where implemented, the results of the correction were documented. Relative costs associated with the interoperability issue were identified, and recommendation\u27s outlining the best method for avoiding these inconsistencies going forward were presented
