Method for controlling the asynchronous transfer mode call in an ATM switching system

A method comprising:

• first requesting that a communication link be established between a first access unit and a second access unit by a route passing through a switching device, said first requesting being performed by said first access unit when said first access unit contacts a first switch unit, said first and second access units being coupled to said switching device but not being included within said switching device, said first switch unit being included within said switching device;
• when said communication link fails to be established by a route passing through a first port wherein said first port couples a second switch unit to said second access unit, transmitting a release signal to said first switch unit, said second switch unit being included within said switching device;
• when said release signal is received, first searching for an address of a second port and then second requesting that said communication link be established by a route passing through said second port, said second requesting being performed by said first switch unit and not being performed by said first access unit, wherein said second port couples said second switch unit to said second access unit;
• and
• enabling said first access unit to communicate with said second access unit along said communication link along said route passing through said second port.

An apparatus comprising:

• a switching device routing signals along a plurality of paths;
• a plurality of switching units being installed in said switching device, said plurality of switching units including first and second switch units, said plurality of switching units enabling said switching device to route signals along said plurality of paths;
• a first communication unit being coupled to said switching device;
• a second communication unit being coupled to said switching device;
• a plurality of ports being installed in said switching device, said plurality of ports coupling said second communication unit with said switching device, said plurality of ports including first and second ports;
• said first communication unit first requesting that a communication link be established between said first communication unit and said second communication unit by a route passing through said switching device;
• when said communication link fails to be established by a route passing through said first port, said first switch unit first searching for an address of said second port and then second requesting that said communication link be established by a route passing through said second port, said second requesting being performed by said first switch unit and not being performed by said first communication unit;
• and
• said first communication unit communicating with said second communication unit through said switching device along said communication link by said route passing through said second port.