Method for extending the crankback procedure to any Asynchronous Transfer Mode system

Method for extending the crankback procedure in an Asynchronous Transfer Mode (ATM) system composed of at least a first data network comprising a plurality of switching nodes interconnected by connection lines and including end switching nodes each being connected to at least a Data Transmission equipment (DTE) and being used either as an entry border node when it is connected to a source DTE or an exit border node when it is connected to a destination DTE, the network using a routing protocol of the type wherein a best route between a source DTE and a destination DTE is determined in a control point associated with the entry border node to which is connected the source DTE and wherein a set-up message is sent by the entry border node, and a second data network including at least one DTE to be used as destination DTE in an exchange of data with a source DTE connected to the first data network and being interconnected with the first data network by means of at least two links not supporting the routing protocol. Such a method consists, when the exit border node of the first data network receives a clearing message on one link indicating that the set-up message has been rejected because the best route is blocked anywhere in the second data network, in building a crankback information element to be added to the clearing message for enabling the entry border node to find an alternate route avoiding the portion of the route which is blocked.