A Deadlock – Free Routing Algorithm for Torus Network

Abstract

TORUS is a n-dimensional network topology. Each dimension will have k nodes.  A routing algorithm determines the sequence of channels for a packet to traverse from the source to destination. A new router design that significantly reduces the main drawback of worm hole switching – latency, is presented in this paper. Worm-hole switching is combined with virtual channel to provide better performance. Packet deadlock is avoided by verifying the freeness of the nodes before sending the packets to that node.

The traditional ‘wormhole switching’ mechanism for routing in the torus network has the disadvantages such as link contention, message latency, need for large buffer size and finally a massive deadlock may appear. The recently proposed ‘clue’ algorithm, has the disadvantages such as difficulty in cut through the link by the packets, says nothing about loss of packets between a hop and storage overhead and complexity in dividing the virtual channels. We proposed an ‘Advanced Clue’ algorithm by combining the concepts of clue and flow controlled clue and also overcome the disadvantages of clue. We use two virtual channels and a buffer which gives a combination of clue and flow controlled clue. We also propose conditions that satisfy the reliability of the packet delivery between hops. The packet will be sent to the next hop and buffered in the current hop. The sending hop will set a timer and wait for the acknowledgement. If the acknowledgement is not arrived till the timer expired then, the packet will be resend, and otherwise the packet will be removed from the buffer.

Keywords: Torus, Virtual channels, Cut – through Switching, Wormhole switching.