Detection of lost packets in switching networks used with scalable coherent interfaces

摘要

The Scalable Coherent Interface (SCI) standard of the Institute of Electrical and Electronics Engineers is intended for fast, high throughput, unidirectional links to high-performance multiprocessor systems. Key elements of the protocol for SCI include: (a) a "new/stale" bit which is generated in a data packet for detecting stale packets to discard; (b) an idle.cc which is an idle bit to be inserted between packets for detecting lost packets which toggles when the idle bit has circulated around the ringlet; and (c) a scrubber node in each operational ring of an SCI network which toggles "new/stale" bits from a "new" state to a stale state when they are received at the scrubber node. The "new/stale" bit is also set to a "new" stale bit when a packet is generated in a source node in a first operational ring for transmission to a target node in a second operational ring. A scrubber node is located as the first node of each operational ring of the network. The new/stale" bit and the idle circulation (idle.cc) is used to keep track of misrouted and lost packets. Each of a plurality of switches of the switching network is assigned to one of a plurality of rows of the switches and to one of a plurality of stages of the switches. Each of the switches has a plurality of input ports and output ports associated therewith. Input ports are coupled to the switches of the input stage, and output ports equal in number to the number of input ports are coupled to the switches of the output stage. The number of switches in a row is equal in number to the number of stages of the switching network. The packets are transmitted from the input ports to the output ports through operational rings that are connected thereto until each of the packets reaches a designated target node.