InterconnectionNetworks详解.pptVIP

Interconnection Networks Overview Physical Layer and Message Switching Network Topologies Metrics Deadlock Livelock Routing Layer The Messaging Layer Interconnection Networks CLUX: A Beowulf Cluster The Practical Problem Example: Embedded Devices Physical Layer and Message Switching Messaging Hierarchy The Physical Layer Data is transmitted based on a hierarchical data structuring mechanism Messages ? packets ? flits ? phits While flits and phits are fixed size, packets and data may be variable sized Flow Control Flow control digit: synchronized transfer of a unit of information Based on buffer management Asynchronous vs. synchronous flow control Flow control occurs at multiple levels message flow control physical flow control Mechanisms Credit based flow control Switching Layer Comprised of three sets of techniques switching techniques flow control buffer management Organization and operation of routers are largely determined by the switching layer Connection Oriented vs. Connectionless communication Generic Router Architecture Virtual Channels Each virtual channel is a pair of unidirectional channels Independently managed buffers multiplexed over the physical channel De-couples buffers from physical channels Originally introduced to break cyclic dependencies Improves performance through reduction of blocking delay Virtual lanes vs. virtual channels As the number of virtual channels increase, the increased channel multiplexing has two effects decrease in header delay increase in average data flit delay Impact on router performance switch complexity Circuit Switching Hardware path setup by a routing header or probe End-to-end acknowledgment initiates transfer at full hardware bandwidth Source routing vs. distributed routing System is limited by signaling rate along the circuits Packet Switching Blocking delays in circuit switching avoided in packet switched networks ? full link utilization in the presence of data Increased storage requirements at the