Abstract: A method and apparatus that allows different likelihoods of call completion during very heavy call loading conditions to be supplied to different customers. Customers are assigned to different levels of service and these levels of service are used to manage call completion in throughout the telecommunication network during very heavy call loading periods. Thus, a securities broker may have a higher likelihood of completing a call near the close of a trading session than the average telephone customer. However, each caller may be offered an opportunity to immediately increase his or her level of service and thus likelihood of completing a call to the highest available level if a call is not completed at the caller's lower level of service.

Abstract: This invention relates to a method and apparatus for controlling overload in a data network. The exemplary embodiment is a Broadband Integrated Services Digital Network (B-ISDN) in which data is transmitted within data cells included in a larger data frame using the Asynchronous Transfer Mode (ATM) protocol. In response to the network detecting overload, the network sends slow down messages to selected virtual channels to decrease their data rates. The network also acts to block or decrease resource allocations to transmission requests that are likely to overload the network.