Patent ID: 7120506

Claim:
Communication method for transmitting digital information cells ( 20 ) and data cells ( 21 ) in asynchronous transmission mode (ATM) in an ATM communication system comprising two or more end stations ( 13 , 14 ) and one or more switches ( 11 , 84 – 87 ), a source end station ( 13 ) and a destination end station ( 14 ) of the end stations ( 13 , 14 ) being connected to one another by means of links ( 16 – 18 , 34 – 37 ) by way of one or more of the switches, the source end station ( 13 ) and each switch for setting up a connection between the source end station ( 13 ) and the destination end station ( 14 ), starting at the source end station ( 13 ), delivering a signalling message ( 24 ) to a next switch or the destination end station ( 14 ), as the case may be, the signalling message ( 24 ) being formed by several information cells ( 20 ), the signalling message ( 24 ) comprising several information elements (IEs), a traffic-contract-kind information element (IE) containing an indication which indicates a kind of traffic contract (ATC) requested from a next switch or the destination end station ( 14 ), each switch processing, in accordance with an indication received by the switch, a traffic flow following the signalling message and consisting of data cells, and a kind of traffic contract requested by the source end station ( 13 ) and a kind of traffic contract requested from the destination end station ( 14 ) being one and the same end-station traffic-contract kind, characterised in that, when a switch or the destination end station does not support a kind of traffic contract requested therefrom, but does support another kind of traffic contract which is not more unfavourable than the end-station traffic-contract kind, the signalling message, preceding delivery thereof to the switch or the destination end station from which the kind of traffic contract is requested, is converted by: in so far as the indication is not yet present in the signalling message, adding, to the signalling message, an indication which designates the other kind of traffic contract as the kind of contract requested, and when the signalling message contains an indication which designates the other kind of traffic contract, but not as the kind of traffic contract requested, removing from the signalling message the indication for the kind of traffic contract immediately preceding the conversion.