Abstract: Methods and apparatus are disclosed for distributing flow control information in a packet switching system. In one packet switching system, flow control information is collected in a data structure in the first stage switching elements. Each of these switching elements transmit data from the flow control data structure as small messages or in fields included in packets being sent across multiple statically allocated paths. Flow control information is received by next stage elements, which are programmed to forward only flow control information received from a limited number of components or over a limited number of paths. The first stage switching elements may also periodically or occasionally delay sending flow control information or send a dummy message or information to accommodate bandwidth transmission differences between components of the packet switching system, including to accommodate bandwidth variations caused by plesiochronous timing across the network.

Abstract: Methods and apparatus are disclosed for using barrier phases to synchronize processes and components in a packet switching system, including, for example, but not limited to the use of barrier phases in the coordinated timing of the sending of information (e.g., flow control information) within a packet switching system, and the use of barrier phases in a packet sequence number windowing protocol. In one implementation, elements are assigned to one of multiple ordered sets of a barrier groups, wherein each element of a barrier group must be set to a common barrier state before any element of a next a barrier group can switch to a next barrier state, and once all elements of a particular barrier group switch to a new barrier state, all the elements of the next barrier group begin to switch to the next barrier state.

Abstract: Methods and apparatus are disclosed for using barrier phases to limit the disorder of packets which may be used in a computer or communications system. In one packet switching system, source nodes include an indication of their current barrier state in sent packets. For each barrier state, a predetermined range of sequence numbers may be used or a predetermined number of packets may be sent by a source node. The source, destination, and switching nodes are systematically switched between barrier phases, which is typically performed continuously in response to the flow of barrier request and barrier acknowledgement packets or signals. Each source node broadcasts to all forward connected nodes a barrier request to change to a next barrier state. After a switching node has received a barrier request on all incoming links, the switching node propagates the barrier request.