Asynchronous transfer mode switch providing pollstate status information

A method of operating an ATM switch in which both an origination switch port and a destination switch port are connected to a switch core, the switch core including a first set of cross point buffers for storing service cells received from the origination switch port and a second set of cross point buffers from which service cells are obtained for the destination switch port, the method comprising:

• transmitting a retrieve pollstate control cell from the originating switch port to the switch core;
• transmitting a pollstate status control cell from the switch core to the originating switch port in response to receipt of the retrieve pollstate control cell, the pollstate status control cell including an indication of status of the cross point buffers of the first set;
• transmitting a service cell from the originating switch port to the switch core for storage in one of the cross point buffers of the first set in accordance with the indication of the status as provided in the pollstate status control cell;
• reading out the service cell from the one of the cross point buffers to the destination switch port and providing an indication of vacancy of the one of the cross point buffers;
• transmitting a pollstate release control cell from the switch core to the originating switch port upon the indication of vacancy of the one of the cross point buffers;
• wherein the retrieve pollstate control cell, the pollstate status control cell, and the pollstate release control cell are either originated or terminated at a row column unit of the switch core and are not switchable through the switch core.