Invention Grant
US08089959B2 Method and apparatus to schedule packets through a crossbar switch with delay guarantees 有权
通过具有延迟保证的交叉开关来安排分组的方法和装置

  • Patent Title: Method and apparatus to schedule packets through a crossbar switch with delay guarantees
  • Patent Title (中): 通过具有延迟保证的交叉开关来安排分组的方法和装置
  • Application No.: US11802937
    Application Date: 2007-05-29
  • Publication No.: US08089959B2
    Publication Date: 2012-01-03
  • Inventor: Ted Henryk Szymanski
  • Applicant: Ted Henryk Szymanski
  • Main IPC: H04Q11/00
  • IPC: H04Q11/00
Method and apparatus to schedule packets through a crossbar switch with delay guarantees
Abstract:
A method for scheduling cell transmissions through a switch with rate and delay guarantees and with low jitter is proposed. The method applies to a classic input-buffered N×N crossbar switch without speedup. The time axis is divided into frames each containing F time-slots. An N×N traffic rate matrix specifies a quantized guaranteed traffic rate from each input port to each output port. The traffic rate matrix is transformed into a permutation with NF elements which is decomposed into F permutations of N elements using a recursive and fair decomposition method. Each permutation is used to configure the crossbar switch for one time-slot within a frame of size F time-slots, and all F permutations result in a Frame Schedule. In the frame schedule, the expected Inter-Departure Time (IDT) between cells in a flow equals the Ideal IDT and the delay jitter is bounded and small. For fixed frame size F, an individual flow can often be scheduled in O(log N) steps, while a complete reconfiguration requires O(N log N) steps when implemented in a serial processor. An RSVP or Differentiated Services-like algorithm can be used to reserve bandwidth and buffer space in an IP-router, an ATM switch or MPLS switch during a connection setup phase, and the proposed method can be used to schedule traffic in each router or switch. Best-effort traffic can be scheduled using any existing dynamic scheduling algorithm to fill the remaining unused switch capacity within each Frame. The scheduling algorithm also supports multicast traffic.
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