Analysis and implementation of hybrid switching

Abstract

Abstract-The switching scheme of a point-to-point network determines how packets flow through each node, and is a primary element in determining the networks performance. In this paper, we present and evaluate a new switching scheme called hybrid switching. Hybrid switching dynamically combines both virtual cut-through and wormhole switching to provide higher achievable throughput than wormhole alone, while significantly reducing the buffer space required at intermediate nodes when compared to virtual cut-through. This scheme is motivated by a comparison of virtual cut-through and wormhole switching through cycle-level simulations, and then evaluated using the same methods. To show the feasibility of hybrid switching, as well as to provide a common base for simulating and implementing a variety of routing and switching schemes, we have designed SPIDER, a communication adapter built around a custom ASIC called the Programmable Routing Controller (PRC).

Flow control for fully adaptive routing††Part of this research was first presented at the 18th IEEE International Symposium on High Performance Computer Architecture (HPCA-2012) [32]. The journal extension edition of the HPCA-2012 paper was published in IEEE Transactions on Parallel and Distributed Systems [33].

“…Even with DAMQ, allowing multiple packets to reside in one VC may lead to deadlock similar to that in Figure 6.3 for fully adaptive routing in wormhole networks. There are some hybrid flow controls [30,45,47]. WPF can be viewed as a hybrid mechanism combining wormhole flow control and VCT flow control.…”

“…WPF is complementary to DAMQ as it ensures deadlock freedom. Hybrid switching [45] and buffered wormhole [47] remove a blocked packet to release held physical channels by using either the processing node memory [45] or a central buffer [47]. There are some hybrid flow controls [30,45,47].…”

On Bandwidth Adjusted Multicast Communications in Pipeline Router Architecture

“…This way, packet forwarding is possible at any node even though the entire packet has not yet arrived completely from the upstream links allowing pipelining of packet transmissions [8,19]. In case of virtual cut-through switching with pipelined transmissions, it can forward partially received packets immediately after the header processing is done giving us the advantage of low latency delivery and lesser requirements on buffer space [17] when input buffer and output port are free. The other advantage is that it allows buffering of packets when blocked due to busy output ports and these buffered packets are removed from the network releasing the channel for other packets destined to different output ports.…”

Mediaworm: a qos capable router architecture for clusters

“…Metro [29] and Ariadne [30] employ the pipelined circuit switching (PCS) technique, while the latter is fully adaptive and tolerates link and switch faults. A hybrid switch including both wormhole and VCT was designed in [31]. All these routers are primarily designed to minimize average message latency and improve the network throughput.…”