Control architecture of a multi-node circuit- and packet-switching system

Abstract

A distributed control arrangement for a multi-mode circuit-switching or circuit- and packet-switching system avoids disadvantages attendant to a centralized control center and offers flexibility in the sourcing of communication-routing information. The switching system communicatively interconnects a plurality of communication endpoints, such as PBXs, and includes a plurality of circuit-switching units interconnected with each other and with the endpoints by at least one communication medium. Control is effected through a plurality of logical links of the LAPD communication protocol, one of which extends through the medium between each pair of adjacent units and of adjacent unit and endpoint. Each unit is responsive to receipt of a messeage that specifies a route of a circuit-switched communication path through the system, including through the receiving unit. The message contains a plurality of address bytes each one of which specifies a segment of the route through the system: the bytes specify a sequence of system nodes through which the path extends. In response to receiving the message over a first link that extends to the receiving unit from another unit or an endpoint, the receiving unit establishes a communication path for the communication from the adjacent unit or endpoint from which the first link extends, through the receiving unit, and to an adjacent unit or endpoint-en-route of the communication. The individual unit then also sends the received message to the adjacent en-route unit or endpoint, over a second link which extends between the individual unit and the adjacent en-route unit or endpoint.