Power saving is required for interconnects of modern PC clusters as well as the performance improvement. To reduce the power consumption of switches with maintaining the performance, on/off link regulations that activate and deactivate the links based on the traffic load have been widely developed in interconnection networks. Depending on which operation is selected, link activation or deactivation, the available network resources are changed, thus requiring paths to be reconfigured. To maintain deadlock freedom of packet transfers, connectivity, and performance during the path changes, we propose to apply dynamic reconfiguration techniques that process packet transfer uninterruptedly to power-aware on/off interconnection networks. The dynamic network reconfiguration techniques stabilize the update of paths that are quite crucial to use power-aware on/off link techniques in interconnects of PC clusters. We investigate the performance and behavior of network reconfiguration technique as soon as the link activation or deactivation occurs. Evaluation results show that the simple dynamic reconfiguration techniques slightly reduce the peak packet latency and reconfiguration time of the change compared with existing static reconfiguration in on/off interconnection networks. A reconfiguration technique called Double Scheme reduces by up to 95% the peak packet latency caused by the on/off link operation.
[Show abstract][Hide abstract] ABSTRACT: High-speed local area networks (LANs) consist of a set of switches
interconnected by point-to-point links, and hosts linked to those
switches through a network interface card. High-speed LANs may change
their topology due to switches being turned on/off, hot expansion, link
remapping, and component failures. In these cases, a distributed
reconfiguration protocol analyzes the topology, computes the new routing
tables, and downloads them to the corresponding switches. Unfortunately,
in most cases, user traffic is stopped during the reconfiguration
process to avoid deadlock. These strategies are called static
reconfiguration techniques. Although network reconfigurations are not
frequent, static reconfiguration such as this may take hundreds of
milliseconds to execute, thus degrading system availability
significantly. Several distributed real-time applications have strict
communication requirements; Distributed multimedia applications have
similar, although less strict, quality of service (QoS) requirements.
Both stopping packet transmission and discarding packets due to the
reconfiguration process prevent the system from satisfying the above
requirements. Therefore, in order to support hard real-time and
distributed multimedia applications over a high-speed LAN, we need to
avoid stopping user traffic and discarding packets when the topology
changes. In this paper, we propose a new deadlock-free distributed
reconfiguration protocol that is able to asynchronously update routing
tables without stopping user traffic. This protocol is valid for any
topology, including regular as well as irregular topologies. It is also
valid for packet switching as well as for cut-through switching
techniques and does not rely on the existence of virtual channels to
work. Simulation results show that the behavior of our protocol is
significantly better than for other protocols based on stopping user
IEEE Transactions on Parallel and Distributed Systems 03/2001; DOI:10.1109/71.910868 · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper develops theoretical support useful for determining deadlock properties of dynamic network reconfiguration techniques and also serves as a basis for the development of design methodologies useful for deriving deadlock-free reconfiguration techniques. It is applicable to interconnection networks typically used in multiprocessor servers, network-based computing clusters, and distributed storage systems, and also has potential application to system-on-chip networks. This theory builds on basic principles established by previous theories while pioneering new concepts fundamental to the case of dynamic network reconfiguration.
IEEE Transactions on Parallel and Distributed Systems 06/2005; 16(5-16):412 - 427. DOI:10.1109/TPDS.2005.58 · 2.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Exploitation of the wiring flexibility in Networks of Workstations demands configuration methods that can handle dynamic changes in irregular topologies. During reconfiguration of a network based on virtual cut-through or wormhole switching, however deadlocks in the transition phase between the old and the new routing function must be avoided. The avoidance of such deadlocks will in general make the performance of the network suffer during reconfiguration. Keeping reconfiguration time as short as possible, and leaving as much as possible of the network untouched is therefore of importance. We propose a method for dynamic reconfiguration of networks using up*/down* routing that aims at reducing the consequences of reconfiguration. This is done by identifying a restricted parr of the network, the skyline, as the only part where a full reconfiguration is necessary. This means that most of the network does not need to take part in the reconfiguration at all (other than adding entries for new nodes, and removing entries for removed nodes). Experiments show that for the most frequent configuration changes the skyline will be empty in 85-95% of the cases, leaving the whole of the network operational through the entire reconfiguration. For the most dramatic changes in topology-the addition of a link connecting two previously disjoint networks-an average of 90% of the links can start using the new routing function immediately for some topologies. Our approach is in principle orthogonal to other approaches, thus existing methods for dynamic reconfiguration can be applied in the reconfiguration of the skyline
Parallel Processing, 2000. Proceedings. 2000 International Conference on; 02/2000
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