Customer Affecting Incidents and Blocking Defects Per Million - Series E: Overall Network Operation Telephone Service Service Operation and Human Factors - Quality of Service Network Management and Traffic Engineering - Network Management - Checking the Q
In switched networks, significant blocking can occur whenever there is a loss of capacity due to some form of network outage. These outages can be loosely called Customer Affecting incidents or CAIs. CAIs cause focused blocking over and above those that occur due to engineered blocking. Calls blocked due to CAI can be termed "Defects". An appropriate network measure is the Defects Per Million (DPM) of call attempts.