N-by-N "knockout" switch for a high-performance packet switching system with variable length packets
First Claim
1. A switching arrangement employing decentralized control and distributed routing of variable-length packets of information, the switching arrangement comprising:
- a plurality of N output terminals (12);
a plurality of N input terminals (10) for receiving N separate input signals, each input signal comprising variable-length packets of information in a time division sequence; and
switching means (11) disposed to receive up to N overlapping variable-length packets of information from the N input terminals during a predetermined time period and for routing each of the packets of information to the destined one of the N output terminals, the switching means being responsive to the reception of a plurality of up to N overlapping variable-length packets of information destined for a particular output terminal for storing up to L of such packets of information for subsequent transmission to the destined output terminal on a first-in, first-out basis from packets of information stored in any subsequent predetermined time period while discarding any overlapping variable-length packets of onformation above the number L, where L<
N.
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Accused Products
Abstract
The present invention relates to an N-input, N-output "Knockout" packet switch (11) which uses decentralized control and distributed routing for routing high-speed, time-multiplexed, variable-length packets of information from the N inputs to the N outputs. More particularly, within the switch, the N input signals are separately synchronized such that the start of each arbitrarily arriving variable-length packet is synchronized to the start of a next mini time period of a sequence of mini time periods common to all inputs. The synchronized N input signals then propagate along separate broadcast buses (14) to each of N bus interface units (15) which include N packet filters (20), a concentrator (21) and a shared buffer (22) capable of processing variable-length packets. Each bus interface unit is associated with a separate one of the N outputs (12) of the switch, and the N packet filters therein are each associated with a separate one of the N broadcast buses for detecting if a packet on the associated bus is destined for the associated switch output. The concentrator is used to (a) reduce the number of separate buffers needed to receive packets which may arrive simultaneously and are destined for the associated output, and (b) only directs a maximum of L concurrently arriving packets to the shared buffer while discarding, or "knocking" out, the remainder. Contending packets at the output of the concentrator are stored in the shared buffer before placement on the output line on a first-in, first-out basis. The discarded packet rate of the "knockout" switch can be made as small as desired and latency of packets in the switch is the smallest achievable by any comparable switch.
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Citations
11 Claims
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1. A switching arrangement employing decentralized control and distributed routing of variable-length packets of information, the switching arrangement comprising:
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a plurality of N output terminals (12); a plurality of N input terminals (10) for receiving N separate input signals, each input signal comprising variable-length packets of information in a time division sequence; and switching means (11) disposed to receive up to N overlapping variable-length packets of information from the N input terminals during a predetermined time period and for routing each of the packets of information to the destined one of the N output terminals, the switching means being responsive to the reception of a plurality of up to N overlapping variable-length packets of information destined for a particular output terminal for storing up to L of such packets of information for subsequent transmission to the destined output terminal on a first-in, first-out basis from packets of information stored in any subsequent predetermined time period while discarding any overlapping variable-length packets of onformation above the number L, where L<
N. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification