Method and apparatus for controlling quality of service in an ATM network

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The present invention encompasses a method of and apparatus for implementing a switching network with a plurality of interconnected switching nodes and communications links.
When a transfer is to be made between a calling end and a called end, a calling end system generates a call request.
A switching node attached to that calling end system defines a network path to the calling end system and transfers a call establishment message to successive switching nodes over that network path for the virtual connection.
At each switching node a selection of one call transforming process available at that node is made in response to the characteristics of an outgoing communications link to a succeeding switching node in the network path, the quality of service requirements for the virtual connection, and the expected effects of each transforming process on the ATM cells.
The switching node also determines the expected quality of service from the calling end system to the succeeding switching node.
If the defined network path for the virtual connection is capable of meeting the quality of service requirements, the switching node updates the expected quality of service and forwards the updated call establishment message to the succeeding switching node.
Otherwise the switching node effects a release of the call over that virtual connection.
FIG.
1 schematically depicts a typical ATM switching network 10 between a calling end 12 and a called end 14 that can incorporate this invention and that serves as a basis for establishing certain terms that are useful in understanding this invention.
This particular switching network comprises a plurality of switching nodes, with switching nodes 15, 16, 17 and 20 being shown for purposes of this explanation, and a plurality of interconnecting communications links.
A calling end system 21 connects to the network through a communications link 22 that attaches to the switching node 15.
Similarly, a called end system 23 connects to the switching node 17 by means of a communications link 24