Minimum latency cut-through switch fabric
First Claim
1. In a packet communications switch fabric, a method for cut-through packet routing, the method comprising:
- at an input port card ingress port, accepting information packets including a plurality of cells and addressed to a plurality of output port card egress ports;
routing information packets between port cards on backplane data links through an intervening crossbar;
at the input port card, maintaining a credit counter for each port card egress destination;
decrementing the counter in response to transmitting cells in a packet from the input port card; and
,incrementing the counter in response to transmitting cells from the packet at the output port card.
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Accused Products
Abstract
A system and method are provided for cut-through packet routing in a packet communications switch fabric. The method comprises: accepting information packets addressed to a plurality of output port card egress ports at an input port card ingress port; routing information packets between port cards on backplane data links through an intervening crossbar; maintaining a credit counter for each port card egress destination, at the input port card; decrementing the counter in response to transmitting cells in a packet from the input port card; and, incrementing the counter in response to transmitting cells from the packet at the output port card. In some aspects of the method, accepting information includes buffering the packets in an ingress memory subsystem (iMS). Routing information includes the iMS transmitting buffered packets on a selected backplane data link. Decrementing the counter includes the iMS communicating with the iPQ in response to transmitting a cell.
107 Citations
23 Claims
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1. In a packet communications switch fabric, a method for cut-through packet routing, the method comprising:
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at an input port card ingress port, accepting information packets including a plurality of cells and addressed to a plurality of output port card egress ports; routing information packets between port cards on backplane data links through an intervening crossbar; at the input port card, maintaining a credit counter for each port card egress destination; decrementing the counter in response to transmitting cells in a packet from the input port card; and
,incrementing the counter in response to transmitting cells from the packet at the output port card. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In a packet communications switch fabric, a system for cut-through packet routing, the system comprising:
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an output port card including; a plurality of egress ports; and
,a plurality of selectable backplane data links; an input port card including; a plurality of ingress ports accepting information packets including a plurality of cells and addressed to the plurality of output port card egress ports; a plurality of selectable backplane data links; a counter that is decremented in response to transmitting cells from a packet on the input port card backplane data links, and incremented in response to transmitting cells from the packet at the output port card egress ports; and
,a crossbar having a plurality of inputs selectively connectable to a plurality of outputs, the plurality of inputs connected to input port card backplane data links and the plurality of outputs connected to output port card backplane data links. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification