Performance Analysis of Virtual Cut - through Switchingin

This paper presents a formal analysis of virtual cut-through in a C-wrapped hexagonal mesh multicomputer, called the HARTS (Hexagonal Architecture for Real{Time Systems), which is currently being built at the Real{Time Computing Laboratory, The University of Michigan. In virtual cut-through, packets arriving at an intermediate node are forwarded to the next node in the route without buuering if a circuit can be established to the next node. The hexagonal mesh is rst characterized using a combinatorial analysis to determine the probability that a packet will establish a cut-through at an intermediate node. Given this parameter the probability distribution function for packet delivery times in HARTS is derived. The delivery times obtained from the analytic model are then compared against results collected from a simulator of the routing hardware designed for use in HARTS. The results from both the analytic model and the simulator further reinforce the choice of the virtual cut-through routing scheme for use in HARTS. Any opinions, ndings and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reeect the view of the ONR.