Cisco Technology, Inc.

Jonathan E Michelson

John Joseph Williams, Jr

Thomas Dejanovic

John Andrew Fingerhut

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.

Method and apparatus for distributing information within a packet switching system

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.

Method and apparatus for using barrier phases to synchronize processes and components in a packet switching system

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. Upon receiving barrier requests over all links, each destination stage relays an acknowledgement message to all connected source elements, which then send a barrier acknowledgement in much the same way, and each source element changes its barrier state causing the sequence number or counting space to be reset, and newly sent packets to indicate the new barrier state. Upon receiving all its barrier acknowledgement messages, each destination stage changes its barrier state, and then the destination can manipulate (e.g., resequence, reassemble, send, place in an output queue, etc.) packets marked with the previous barrier state as it knows that every packet from the previous barrier state has been received. This transition of barrier phases and limiting the number of packets sent per barrier phases may be used to limit the range of the sequence number space and the size of outgoing, resequencing, and reassembling buffers, as well providing a packet time-out mechanism which may be especially useful when non-continuous sequence numbers or time-stamps are included in packets for resequencing and/or reassembly purposes.

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Sunnyvale, CA, United States of America

Jonathan E Michelson