@inproceedings {27850,
	title = {Apprentissage auto-supervis{\'e} pour la d{\'e}tection d{\textquoteright}actions ill{\'e}gales lors de la surveillance du trafic maritime},
	journal = {Applications Pratiques de l{\textquoteright}Intelligence Artificielle},
	year = {2021},
	publisher = {AFIA},
	author = {Bernab{\'e}, Pierre and Gotlieb, Arnaud and Legeard, Bruno and Frank Olaf {Sem-Jacobsen} and Spieker, Helge}
}
@article {Simula.simula.838,
	title = {An Efficient, Low-Cost Routing Framework for Convex Mesh Partitions to Support Virtualisation},
	journal = {ACM Transactions on Embedded Computing Systems},
	volume = {12},
	number = {4},
	year = {2013},
	month = {June},
	publisher = {ACM},
	abstract = {At the core of an efficient chip multiprocessors (CMP) is support for unicast and multicast routing, low implementation costs, and the ability to isolate concurrent applications with maximum utilization of the CMP. We present an efficient logic-based unicast and multicast routing algorithm that guarantees isolation of local application traffic within any near-convex region on the chip, and the algorithms to recognize supported partitions and configure the cores accordingly. Evaluations show that the routing algorithm has a 57 percent; more compact implementation than a recent multicast solution with the same coverage, and it achieves 5 percent; higher throughput with 13 percent; lower latency.},
	author = {Frank Olaf {Sem-Jacobsen} and Samuel Rodrigo {Mocholi} and Skeie, Tor and Strano, Alessandro and Bertozzi, Davide}
}
@article {Simula.simula.764,
	title = {Enabling Power Efficiency Through Dynamic Rerouting On-Chip},
	journal = {ACM Transactions on Embedded Computing Systems},
	volume = {12},
	number = {4},
	year = {2013},
	month = {June},
	publisher = {ACM},
	abstract = {Networks-on-chip (NoCs) are key components in many-core chip designs. Dynamic power-awareness is a new challenge present in NoCs that must be efficiently handled by the routing functionality as it introduces irregularities in the commonly used 2-D meshes. In this article, we propose a logic-based routing algorithm, iFDOR, oriented towards dynamic powering down one region within every application partition on the chip through dynamic rerouting, with low implementation costs. Results show that we can successfully shutdown an arbitrary rectangular region within an application partition without significant impact on network performance.},
	author = {Frank Olaf {Sem-Jacobsen} and Samuel Rodrigo {Mocholi} and Strano, Alessandro and Skeie, Tor and Bertozzi, Davide and Gilabert, Francisco}
}
@misc {19100,
	title = {Allocating Irregular Partitions in Mesh-Based On-Chip Networks},
	year = {2012},
	publisher = {unknown},
	address = {OMHI 2012 Workshop at Euro-Par},
	abstract = {Modern CMPs require sophisticated resource management in order to provide good utilisation of the chip resources. There exists good allocation algorithms for compute clusters, but these are restricted to specific routing algorithms and not easily transferable to the on-chip domain. We present a novel resource allocation algorithm, TSB, that allows petitions with any shape that is supported by an algorithm implemented using LBDR/uLBDR, and show that this has low complexity and comparable utilisation to UDFlex.},
	author = {Samuel Rodrigo {Mocholi} and Frank Olaf {Sem-Jacobsen} and Skeie, Tor}
}
@inproceedings {Simula.simula.1348,
	title = {Cost-Effective Contention Avoidance in a CMP With Shared Memory Controllers},
	journal = {Proceedings of Euro-Par 2012},
	year = {2012},
	month = {May},
	pages = {741-752},
	publisher = {Springer Berlin Heidelberg},
	type = {Conference},
	abstract = {Efficient CMP utilisation requires virtualisation. This forces multiple applications to contend for the same network resources and memory bandwidth. In this paper we study the cause and effect of network congestion with respect to traffic local to the applications, and traffic caused by memory access. This reveals that applications close to the memory controller suffer because of congestion caused by memory controller traffic from other applications. We present a simple mechanism to reduce head-of-line blocking in the switches, which efficiently reduces network congestion, increases network performance, and evens out the performance differences between the CMP applications.},
	keywords = {Conference},
	author = {Rodrigo, Samuel and Frank Olaf {Sem-Jacobsen} and Tatenguem, Herv{\'e} and Skeie, Tor and Bertozzi, Davide},
	editor = {Kaklamanis, Christos and Papatheodorou, Theodore and Paul G. {Spirakis}}
}
@inproceedings {Simula.simula.1554,
	title = {Discovery and Routing of Degraded Fat-Trees},
	journal = {2012 13th International Conference on Parallel and Distributed Computing, Applications and Technologies},
	year = {2012},
	month = {December},
	pages = {689-694},
	publisher = {IEEE Computer Society},
	type = {Conference},
	address = {Los Alamitos},
	abstract = {The fat-tree topology has become a popular choice for InfiniBand enterprise systems due to its deadlock freedom, fault-tolerance and full bisection bandwidth. In the HPC domain, InfiniBand fabric is used in almost 42\% of the systems on the latest Top 500 list, and many of those systems are based on the fat-tree topology. Despite the popularity of the fat-tree topology, little research has been done to compare the behavior of InfiniBand routing algorithms on degraded fat-tree topologies. In this paper, we identify the weaknesses of the current fat-tree routing and propose enhancements that liberalize the restrictions imposed on the routed fabric. Furthermore, we present a thorough analysis of non-proprietary routing algorithms that are implemented in the InfiniBand Open Subnet Manager. Our results show that even though the performance of a fat-tree routed network deteriorates predictably with the number of failed links, fat-tree routing algorithm is still the best choice for severely degraded fat-tree fabrics.},
	keywords = {Conference},
	author = {Bogdanski, Bartosz and Bj{\o}rn Dag {Johnsen} and Reinemo, Sven-Arne and Frank Olaf {Sem-Jacobsen}},
	editor = {Shen, Hong and Sang, Yingpeng and Li, Yidong and Qian, Depai and Albert Y. {Zomaya}}
}
@misc {Simula.simula.1264,
	title = {Fat-Trees and Dragonflies - a Perspective on Topologies},
	howpublished = {Contributed talk at the HPC Advisory Council Switzerland Workshop, Lugano, Switzerland.},
	year = {2012},
	month = {March},
	abstract = {One of the foundations of any HPC cluster is the network topology. The choice of topology is dictated by properties such as cost, network technology, and target applications. For InfiniBand (IB) the Fat-tree is the dominating topology, but recently we have also seen IB clusters based on a 3d Torus. From time to time new topologies are invented and in this talk we will have a closer look at the recently proposed Dragon-fly topology and compare it with the well established Fat-tree topology.},
	keywords = {Workshop},
	author = {Reinemo, Sven-Arne and Frank Olaf {Sem-Jacobsen} and Skeie, Tor}
}
@article {Simula.simula.864,
	title = {SFtree: a Fully Connected and Deadlock Free Switch-to-Switch Routing Algorithm for Fat-Trees},
	journal = {ACM Transactions on Architecture and Code Optimization},
	volume = {8},
	number = {4},
	year = {2012},
	month = {January},
	publisher = {ACM},
	abstract = {Existing fat-tree routing algorithms fully exploit the path diversity of a fat-tree topology in the context of compute node traffic, but they lack support for deadlock free and fully connected switch-to-switch communication. Such support is crucial for efficient system management, for example in InfiniBand (IB) systems. With the general increase in system management capabilities found in modern InfiniBand switches, the lack of deadlock free switch-to-switch communication is a problem for fat-tree based IB installations because management traffic might cause routing deadlocks that bring the whole system down. This lack of deadlock free communication affects all system management and diagnostic tools using LID routing. In this paper, we propose the sFtree routing algorithm that guarantees deadlock free and fully connected switch-to-switch communication in fat-trees while maintaining the properties of the current fat-tree algorithm. We prove that the algorithm is deadlock free and we implement it in OpenSM for evaluation. We evaluate the performance of the sFtree algorithm experimentally on a small cluster and we do a large-scale evaluation through simulations. The results confirm that the sFtree routing algorithm is deadlock free and show that the impact of switch-to-switch management traffic on the end-node traffic is negligible.},
	doi = {http://dx.doi.org/10.1145/2086696.208673},
	author = {Bogdanski, Bartosz and Reinemo, Sven-Arne and Frank Olaf {Sem-Jacobsen} and Ernst Gunnar {Gran}}
}
@inproceedings {Simula.simula.1500,
	title = {A Theory and Methodology for Combining Data Centre Networks},
	journal = {In proceedings of IEEE International Conference on High Performance Computing (HiPC)},
	year = {2012},
	pages = {1-8},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Existing methods for routing of interconnection networks are optimized for a small group of well defined topologies. Currently, system owners and system integrators are looking for ways to connect two or more existing topologies into one, and thereby create a unified system out of several subsystems. Such integration of multiple networks is supported through e.g. The subnet routing functionality i InfiniBand. In this paper we show that the routing problem of such integration is unsolved, because the integration of two deadlockfree subsystems may lead to routing deadlock. Thereafter we present a theory and a methodology for combining multiple networks in a deadlock-free manner. Through experiments we show that the methodology is able to connect different classes of pre-defined topologies with a definable number of interconnecting links. We demonstrate that we are able to maintain the original routing strategy in the sub-networks, and still get close to full utilization of the bridging links. Finally we show that the methodology is computationally feasible.},
	isbn = {978-1-4673-2372-7},
	doi = {10.1109/HiPC.2012.6507493},
	author = {Frank Olaf {Sem-Jacobsen} and Lorentzen, Ralph and Lysne, Olav}
}
@inproceedings {Simula.simula.1134,
	title = {Topology Agnostic Dynamic Quick Reconfiguration for Large-Scale Interconnection Networks},
	journal = {Proceedings of The 12th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing},
	year = {2012},
	month = {May},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Toleration of faults in the interconnection networks is of vital importance in todays huge computer installations. Still, the existing solutions are short of being satisfactory. They require that the system defaults into a routing algorithm that is inferior to the original, either in terms of performance, or in terms of the need for virtual channels, or both. Furthermore, since support for dynamic reconfiguration is not supported in current hardware, existing methods require the system to be halted while reconfiguration takes place in order to avoid deadlocks. In this paper we present a method that efficiently generates a new routing function in the presence of faults. The new routing function only reroutes the traffic that is affected by the fault, so that the performance of the original routing function is preserved to the extent possible. No specific functionality in the switches is required, we only require exactly the same number of virtual channels in the presence of faults as the original routing algorithm did. Finally, the new routing function is compatible with the old one, so that deadlock free dynamic transition between the old and the new routing function is immediately available. This means that our solution can easily be implemented on current InfiniBand platforms, e.g. through the OFED software stack. We demonstrate that the method is workable for meshes, tori and fat-trees, and that it is able to guarantee one-fault tolerance for all of these topologies.},
	author = {Frank Olaf {Sem-Jacobsen} and Lysne, Olav},
	editor = {Balaji, Pavan and Buyya, Rajkumar}
}
@techreport {Simula.simula.766,
	title = {Appendix to Enabling Power Efficiency Through Dynamic Rerouting On-Chip},
	year = {2011},
	month = {September},
	publisher = {Simula Research Laboratory},
	author = {Frank Olaf {Sem-Jacobsen} and Samuel Rodrigo {Mocholi} and Strano, Alessandro and Skeie, Tor and Bertozzi, Davide and Gilabert, Francisco}
}
@inbook {Simula.simula.882,
	title = {Direct Networks},
	booktitle = {Encyclopedia of Parallel Computing},
	year = {2011},
	month = {January},
	pages = {1304-1310},
	publisher = {Springer},
	organization = {Springer},
	chapter = {Unknown},
	isbn = {978-0-387-09844-9},
	author = {Lysne, Olav and Frank Olaf {Sem-Jacobsen}},
	editor = {Padua, David}
}
@article {Simula.ND.64,
	title = {Dynamic Fault Tolerance in Fat-Trees},
	journal = {IEEE Transactions on Computers},
	volume = {60},
	number = {4},
	year = {2011},
	month = {April},
	pages = {508-525},
	publisher = {IEEE},
	abstract = {Fat-trees are a very common communication architecture in current large-scale parallel computers. The probability of failure increases with the number of components. We present a routing method for deterministically and adaptively routed fat trees, applicable to both distributed and source routing, that is able to handle several concurrent faults and that transparently returns to the original routing strategy once the faulty components have recovered. The method is local and dynamic, completely masking the fault from the rest of the system. It only requires a small extra functionality in the switches to handle misrouting around a fault. The method guarantees connectedness and deadlock and livelock freedom for up to radix/2 -1 arbitrary simultaneous faults. Our simulation experiments show a graceful degradation of performance as faults are added. Furthermore, they demonstrate that for most fault combinations, our method will even be able to handle significantly more faults beyond the radix/2-1 limit with high probability.},
	doi = {10.1109/TC.2010.97},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav and Duato, Jose}
}
@inproceedings {Simula.ND.303,
	title = {Efficient and Contention-Free Virtualisation of Fat-Trees},
	journal = {IEEE International Symposium on Parallel and Distributed Processing Workshops and Phd Forum},
	year = {2011},
	month = {September},
	pages = {754-760},
	publisher = {IEEE Computer Society Washington},
	type = {Workshop},
	address = {Washington DC, USA},
	abstract = {Maintaining high system utilisation is a key factor for data centres. However, strictly partitioning the datacentre resources to fully isolate the concurrent applications (contention freedom) leads to poor system utilisation because of fragmentation. We present an allocation algorithm for fat-trees (which are commonly found in large-scale data centres) capable of increasing system utilisation while maintaining application isolation. Results show at least a 10\% increase in system utilization compared to regular contention free allocation mechanisms, at the cost of a slight reduction in network performance or application isolation.},
	isbn = {978-0-7695-4577-6},
	author = {Frank Olaf {Sem-Jacobsen} and {\r A}shild Gr{\o}nstad {Solheim} and Lysne, Olav and Skeie, Tor and S{\o}dring, Thomas}
}
@inproceedings {Simula.simula.504,
	title = {IFDOR - Dynamic Rerouting On-Chip},
	journal = {Proceedings of the Fifth International Workshop on Interconnection Network Architecture: On-Chip, Multi-Chip},
	year = {2011},
	month = {January},
	pages = {11-14},
	publisher = {ACM},
	type = {Workshop},
	address = {New York, USA},
	abstract = {Many-core chip design requires flexible routing solutions for the interconnect to handle faults, provide performance partitions, and react to dynamic changes in processing requirements and power/heat distribution. We have developed a logic based rerouting mechanism suitable for tolerating dynamic powering down of regions within the application partition on the chip. This mechanism is combined with the logic based FDOR routing algorithm to create a powerful routing algorithm with low implementation cost. This allows for higher system utilisation through enabling more efficient power management as well as supporting many irregular mesh topologies through flexible virtualisation. Results show that powering down a single switch results in an 8\% throughput reduction in the worst case for the evaluated topology.},
	isbn = {978-1-4503-0272-2},
	author = {Frank Olaf {Sem-Jacobsen} and Samuel Rodrigo {Mocholi} and Skeie, Tor},
	editor = {Flich, Jos{\'e} and Bertozzi, Davide}
}
@inbook {Simula.simula.884,
	title = {Multistage Networks},
	booktitle = {Encyclopedia of Parallel Computing},
	year = {2011},
	month = {January},
	pages = {1316-1321},
	publisher = {Springer},
	organization = {Springer},
	chapter = {Unknown},
	isbn = {978-0-387-09844-9},
	author = {Frank Olaf {Sem-Jacobsen} and Lysne, Olav},
	editor = {Padua, David}
}
@techreport {Simula.simula.852,
	title = {Topology Agnostic Dynamic Quick Reconfiguration for Large-Scale Interconnection Networks},
	year = {2011},
	month = {November},
	publisher = {Simula Research Laboratory},
	abstract = {Toleration of faults in the interconnection networks is of vital importance in todays huge computer installations. Still, the existing solutions are short of being satisfactory. They require that the system defaults into a routing algorithm that is inferior to the original, either in terms of performance, or in terms of the need for virtual channels, or both. Furthermore, since support for dynamic reconfiguration is not supported in current hardware, existing methods require the system to be halted while reconfiguration takes place in order to avoid deadlocks. In this paper we present a method that efficiently generates a new routing function in the presence of faults. The new routing function only reroutes the traffic that is affected by the fault, so that the performance of the original routing function is preserved to the extent possible. We require exactly the same number of virtual channels in the presence of faults as the original routing algorithm did. Finally, the new routing function is compatible with the old one, so that deadlock free dynamic transition between the old and the new routing function is immediately available. This means that our solution can easily be implemented on current InfiniBand platforms, e.g. through the OFED software stack. We demonstrate that the method is workable for meshes, tori and fat-trees, and that it is able to guarantee one-fault tolerance for all of these topologies.},
	author = {Frank Olaf {Sem-Jacobsen} and Lysne, Olav}
}
@inproceedings {Simula.netsys.16,
	title = {Achieving Predictable High Performance in Imbalanced Fat Trees},
	journal = {Proceedings of the 16th IEEE International Conference on Parallel and Distributed Systems},
	year = {2010},
	month = {December},
	pages = {381-388},
	publisher = {IEEE Computer Society},
	type = {Conference},
	abstract = {Abstract-The fat-tree topology has become a popular choice for InfiniBand fabrics due to its inherent deadlock freedom, fault-tolerance and full bisection bandwidth. InfiniBand is used by more than 40\% of the systems on the latest Top 500 list, and many of these systems are based on a fat-tree topology. However, the current InfiniBand fat-tree routing algorithm suffers from flaws that reduce its scalability and flexibility. Counter-intuitively, the achievable throughput per node deteriorates both when the number of nodes in a tree decreases or when the node distribution among leaves is nonuniform. In this paper, we identify the weaknesses of the current enhanced fat-tree routing algorithm in OpenFabrics Enterprise Distribution and we propose extensions to it that alleviate all performance problems related to node distribution. The new algorithm is implemented in OpenSM for real world evaluation and for future contribution to the OpenFabrics community. We demonstrate that our solution allows to achieve a predictable high throughput regardless of the number of nodes and their distribution. Furthermore, the simulations show that our extensions improve throughput up to 30\% depending on topology size and node distribution.},
	isbn = {978-0-7695-4307-9},
	author = {Bogdanski, Bartosz and Frank Olaf {Sem-Jacobsen} and Reinemo, Sven-Arne and Skeie, Tor and Holen, Line and Lars Paul {Huse}},
	editor = {Huang, Xiaoxia}
}
@techreport {Simula.nd.413,
	title = {Dynamic Fault Tolerance in Fat-Trees - Research Note},
	year = {2009},
	month = {November},
	publisher = {Simula},
	abstract = {Fat-trees are a very common communication architecture in current large-scale parallel computers. The probability of failure in these systems increases with the number of components. We present a routing method for deterministically and adaptively routed fat-trees, applicable to both distributed and source routing, that is able to handle several concurrent faults and that transparently returns to the original routing strategy once the faulty components have recovered. The method is local and dynamic, completely masking the fault from the rest of the system. It only requires a small extra functionality in the switches to handle misrouting around a fault. The method guarantees connectedness and deadlock and livelock freedom for up to k -1 arbitrary simultaneous switch and/or link faults where k is half the number of ports in the switches. Our simulation experiments show a graceful degradation of performance as more faults occur. Furthermore, we demonstrate that for most fault combinations, our method will even be able to handle significantly more faults beyond the k-1 limit with high probability.},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav and Duato, Jose}
}
@inproceedings {Simula.ND.367,
	title = {Flexible DOR Routing for Virtualization of Multicore Chips},
	journal = {International Symposium on System-on-Chip},
	year = {2009},
	month = {October},
	publisher = {IEEE},
	type = {Conference},
	abstract = {The expected increase in number of cores on a single chip leads to the necessity of high-performance on chip interconnects (NoC). Furthermore, in order to fully utilize the abundance of cores, the chip is expected to support a number of applications running on the chip simultaneously. It is therefore necessary to partition the chip to support numerous applications without any risk of interference between them. The success of this depends on the flexibility of the underlying routing algorithm. This paper presents a flexible routing algorithm based on dimension ordered routing, which supports a large variety of irregular (2-D and 3-D) mesh topologies. The algorithm provides high efficiency at very low additional complexity, as is confirmed by experimental results.},
	isbn = {978-1-4244-4465-6},
	author = {Skeie, Tor and Frank Olaf {Sem-Jacobsen} and Samuel Rodrigo {Mocholi} and Flich, Jos{\'e} and Bertozzi, Davide and Medardoni, Simone},
	editor = {Nurmi, Jari and Takala, Jarmo and Vainio, Olli}
}
@inbook {Simula.ND.309,
	title = {Scalable Interconnection Networks},
	booktitle = {Simula Research Laboratory - by thinking constantly about it},
	year = {2009},
	pages = {129-162},
	publisher = {Springer},
	organization = {Springer},
	chapter = {14},
	address = {Heidelberg},
	abstract = {A modern supercomputer or large scale server consists of a huge set of processing units and units that perform different forms of input/output and memory functions. These components unite in a complex collaboration to perform the main tasks of the system. Such collaboration requires communication between the components, which is supported by an infrastructure called the interconnection network. This book chapter describes the interconnection networks research activity at Simula the last five years done by the ICON group. ICON has focused on how to connect point-to-point links and switches into scalable network topologies, and how to route packets efficiently in order to yield the highest possible performance. This also poses various requirements regarding fault tolerance, quality of service (QoS), congestion control, virtualization, and other non-functional aspects. ICON\&$\#$39;s research results have been published in several of the most respected IEEE journals and magazines within our field. Furthermore, some of ICON\&$\#$39;s solutions have had a major impact on the routing architecture of modern supercomputers.},
	isbn = {978-3-642-01155-9},
	author = {Lysne, Olav and Skeie, Tor and Reinemo, Sven-Arne and Frank Olaf {Sem-Jacobsen} and Nils Agne {Nordbotten}},
	editor = {Tveito, Aslak and Are Magnus {Bruaset} and Lysne, Olav}
}
@inproceedings {Simula.ND.61,
	title = {Fault Tolerance With Shortest Paths in Regular and Irregular Networks},
	journal = {22nd IEEE International Parallel \& Distributed Processing Symposium},
	year = {2008},
	month = {April},
	publisher = {IEEE},
	type = {Conference},
	abstract = {Fault tolerance has become an important part of current supercomputers. Local dynamic fault tolerance is the most expedient way of tolerating faults by preconfiguring the network with multiple paths from every node/switch to every destination. In this paper we present a local shortest path dynamic fault-tolerance mechanism inspired by a solution developed for the Internet that can be applied to any shortest path routing algorithm such as Dimension Ordered Routing, Fat Tree Routing, Layered Shortest Path, etc., and provide a solution for achieving deadlock freedom in the presence of faults. Simulation results show that 1) for fat trees this yields the to this day highest throughput and lowest requirements on virtual layers for dynamic one-fault tolerance, 2) we require in general few layers to achieve deadlock freedom, and 3) for irregular topologies it gives at most a 10 times performance increase compared to FRoots.},
	isbn = {978-1-4244-1693-6},
	author = {Frank Olaf {Sem-Jacobsen} and Lysne, Olav},
	editor = {Robert, Yves}
}
@inproceedings {Simula.ND.60,
	title = {Maintaining Quality of Service With Dynamic Fault Tolerance in Fat Trees},
	journal = {International Conference on High Performance Computing (HiPC)},
	volume = {1},
	year = {2008},
	month = {december},
	pages = {451-464},
	publisher = {Springer-Verlag},
	type = {Conference},
	address = {Berlin},
	abstract = {A very important ingredient in the computing landscape is Utility Computing Data Centres (UCDCs), large-scale computing system that offers computational services to concurrently running applications. In a UCDC, virtual servers containing a subset of the available resources are dynamically created to fulfil user demands. Typically, each virtual server will have its own service level agreement, which should to the largest extent be unaffected by the behaviour of the all other virtual servers in the system. As UCDC systems increase in size and the mean time between failure decreases, it is becoming an increasingly important challenge to expediently tolerate failures (dynamically), while distributing the effects of the failure amongst the virtual servers according to their service level agreements. In this paper we propose and evaluate a strategy for offering predictable service in fat trees experiencing faults, by reprioritising packets. The strategy is able to distribute the effect of network faults in order to satisfy a number of quality of service demands. These may include guaranteeing that high-priority packets not encountering the fault are unaffected by the fault event, guaranteeing high network throughput for all high-priority traffic, or ensuring that the negative effects of the fault are evenly and fairly spread throughout the network. We find that which demands to favour depends on the computer system and the characteristics of the applications it is running, and that in the presence of a moderate number of faults it is to some degree possible to meet the demands.},
	isbn = {3-54089893-x},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor},
	editor = {Ponnuswamy Sadayappan {Al.}}
}
@phdthesis {Simula.ND.231,
	title = {Towards a Unified Interconnect Architecture: Combining Dynamic Fault Tolerance With Quality of Service, Community Separation, and Power Saving},
	year = {2008},
	month = {August},
	school = {University of Oslo},
	type = {phd},
	abstract = {High-performance computing has, for a decade, been synonymous with parallel computer systems. Whereas parallel systems initially were based on shared memory processing, all current high-performance systems are based on massively parallel processing, utilising a large number of loosely coupled processing units. Any parallel processing relies on a degree of communication, so the network interconnecting the processing units in the computer system has a significant impact on the efficiency of the system. Interconnection networks consist of a large number of switches and links to support the possible communication demands, and so the probability of some part of the system failing has to be considered. Steps must be taken to guarantee that all sources and destinations will be allowed to continue communication even with some failed elements, the system must be fault tolerant. As elements fail, communication patterns in the network will change and affect the quality of service experienced by all traffic in the system. Furthermore, in many cases, single applications need not occupy the entire computer system to perform its calculations. To increase system efficiency, several such applications may be run in parallel on the same system, or parts of the system may be shut down when it is underutilised to save power and cut expenses. When several applications are sharing the same system, there should be a minimal degree of interaction between them. This requires separation of communities and routing containment to guarantee that separate applications do not share network resources, and in the case where this is unavoidable, quality of service must be enforced to provide reliable guarantees to the applications. All these fields have received attention from the academic world, however, most proposed solutions for one problem are not easilly combined with solutions for the other problems. In this thesis, we develop a number of solutions for the different problems and attempt to combine these into a unified architecture. For fault tolerance we develop a number of algorithms based on re-routing locally around failed elements. We considered both specific fat-tree topologies, and a topology agnostic solution. For the fat-tree topology we are able to tolerate \frac{switch\_ports}{2} -1 link or switch faults dynamically with very low response times. We then proceed to evaluate how these mechanisms affect quality of service experienced by traffic flows in the network, and propose and evaluate a number of methods to re-prioritise traffic and maintain quality-of-service guarantees. We also develop a multipath routing scheme for fat-trees. By carefully selecting which path is utilised, we can achieve fault tolerance, separation communities, and power saving. Finally, we describe how a number of the proposed methods can be combined into a unified network architecture that addresses all the challenges we have stated.},
	isbn = {1501-7710},
	author = {Frank Olaf {Sem-Jacobsen}}
}
@inproceedings {Sem-jacobsen.2006.2,
	title = {Combining Source Routing and Dynamic Fault Tolerance},
	journal = {Proceedings of The 18{\textquoteright}th International Symposium on Computer Architecture and High Performance Computing (SBAC-PAD)},
	year = {2006},
	month = {October},
	pages = {151-158},
	publisher = {IEEE Computer Society},
	type = {Conference},
	address = {Washington, DC, USA},
	abstract = {An increasing amount of current and emerging interconnect technologies rely on source routing to forward packets through the network. It is therefore important to develop methods for fault tolerance that are well suited for source routed networks. Dynamic fault tolerance allows the network to remain available through the occurrence of faults, as opposed to static fault tolerance which requires the network to be halted to reconfigure it. Source routing readily supports the source node choosing a different path when a fault occurs, but using this approach, packets already in the network will be lost. Local dynamic fault tolerance, where the packet is routed around the fault locally, would prevent much of the traffic being lost during failures, but this is cumbersome to achieve in source routed networks since packets encountering a fault will need to follow a path different from that encoded in the packet header. In this paper we present a mechanism to achieve local dynamic fault tolerance in source routed fat trees, a topology that has widespread use in supercomputer systems, and compare it with endpoint dynamic fault tolerance. We also show that by combining the two approaches we achieve performance superior to any of the two individually.},
	isbn = {0-7695-2704-3},
	author = {Frank Olaf {Sem-Jacobsen} and Lysne, Olav and Skeie, Tor},
	editor = {Alberto F. {De Souza} and Buyya, Rajkumar and Wagner {Meira, Jr.}}
}
@inproceedings {Sem-jacobsen.2006.1,
	title = {Dynamic Fault Tolerance With Misrouting in Fat Trees},
	journal = {Proceedings of the International Conference on Parallel Processing (ICPP)},
	year = {2006},
	month = {August},
	pages = {33-45},
	publisher = {IEEE Computer Society},
	type = {Conference},
	abstract = {Fault tolerance is critical for efficient utilisation of large computer systems. Dynamic fault tolerance allows the network to remain available through the occurance of faults as opposed to static fault tolerance which requires the network to be halted to reconfigure it. Although dynamic fault tolerance may lead to less efficient solutions than static fault tolerance, it allows for a much higher availability of the system. In this paper we devise a dynamic fault tolerant adaptive routing algorithm for the fat tree, a much used interconnect topology, which relies on misrouting around link faults. We show that we are guaranteed to tolerate any combination of less than (num\_switch\_ports/2) link faults without the need for additional network resources for deadlock freedom. There is also a high probability of tolerating an even larger number of link faults. Simulation results show that network performance degrades very little when faults are dynamically tolerated.},
	isbn = {22},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav and Duato, Jose},
	editor = {Feng, Wu-chi}
}
@inproceedings {Sem-jacobsen.2005.2,
	title = {A Dynamic Fault-Torlerant Routing Algorithm for Fat-Trees},
	journal = {International Conference on Parallel and Distributed Processing Techniques and Applications, Las Vegas, Nevada, USA, June 27-30},
	year = {2005},
	pages = {318-324},
	publisher = {CSREA Press},
	type = {Conference},
	abstract = {The fat tree is a network topology well suited for use as the interconnection network in systems such as parallel computers. Its large number of paths between every source/destination pair gives the fat tree the ability to provide high throughput. This also gives it a high probability of tolerating network faults statically, but few algorithms to dynamically tolerate faults in fattrees have previously been proposed. In this paper we present a deadlock free routing method for providing dynamic fault tolerance through misrouting downwards in the network. We show that the algorithm is one fault-tolerant, and that it with a certain probability can tolerate a large number of faults.},
	isbn = {1-932415-58-0},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav},
	editor = {Hamid R. {Arabnia}}
}
@inproceedings {Sem-jacobsen.2005.1,
	title = {Siamese-Twin: a Dynamically Fault-Tolerant Fat Tree},
	journal = {International Parallel and Distributed Processing Symposium (IPDPS), Denver, Colorado, USA, April 4-8},
	year = {2005},
	publisher = {IEEE Computer Society},
	type = {Conference},
	abstract = {Fat-trees are a special case of multistage interconnection networks with quite good static fault tolerance capabilities. They are however straightforwardly unable to provide local dynamic fault tolerance. In this paper we propose a network topology based on the fat-tree using two parallel networks with crossover links between them in an effort to enable dynamic fault tolerance. We evaluate and compare this topology with two other similar fat-tree topologies and show through simulations that the new topology is able to improve slightly upon the ability to tolerate faults statically. More importantly, we show that the new network topology is the only one of the evaluated topologies able to tolerate one fault dynamically, with a superior network performance in the face of dynamically handled faults.},
	isbn = {0-7695-2312-9},
	author = {Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav and T{\o}rudbakken, Ola and Rongved, Eivind and Bj{\o}rn Dag {Johnsen}}
}
@misc {Theiss.2005.3,
	title = {SIVSS Deliverable 9.2, Research Report on Overall System Archicecture Resilience},
	howpublished = {Sixth framework programme, Commission of the European Communities, Proposal/Contract no.: 002075},
	year = {2005},
	author = {Ingebj{\o}rg Thelin {Theiss} and S{\o}dring, Thomas and {\r A}shild Gr{\o}nstad {Solheim} and Frank Olaf {Sem-Jacobsen}}
}
@inproceedings {ND.5.Sem-Jacobsen.2004,
	title = {Achieving Flow Level QoS in Cut-Through Networks Through Admission Control and DiffServ},
	journal = {Proceedings of the International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA)},
	year = {2004},
	month = {June 21-24},
	pages = {1084-1090},
	publisher = {CSREA Press},
	type = {1},
	address = {Las Vegas, Nevada},
	abstract = {Cluster networks will serve as the future access networks for multimedia streaming, massive multiplayer online gaming, e-commerce, network storage etc. And for those application areas provisioning of Quality of Service (QoS) is becoming and important issue. DiffServ as specified by the IETF is foreseen to be the most prominent concept for providing predictability in the future Internet. To enable seamless interoperation with the higher level IETF concepts the QoS architecture of the lower layers should comply with the DiffServ paradigm as well. Previous work on predictability in cut-through networks has only studied class based QoS. In this paper we set out to achieve flow level QoS using flow aware admission control in combination with a flow negligent DiffServ inspired QoS mechanism. Our results show that flow level bandwidth guarantees are achievable with the use of the Link-by-Link and the Probe based schemes. In addition we are able to achieve an order of magnitude improvement in jitter and latency in individual flows.},
	author = {Frank Olaf {Sem-Jacobsen} and Reinemo, Sven-Arne and Skeie, Tor and Lysne, Olav},
	editor = {Hamid R. {Arabnia}}
}
@inproceedings {ND.5.Reinemo.2003.b,
	title = {Admission Control for DiffServ Based Quality of Service in Cut-Through Networks},
	journal = {Proceedings of the 10th International Conference on High Performance Computing (HiPC 2003)},
	year = {2003},
	month = {December 17-20},
	pages = {118-129},
	publisher = {Springer},
	type = {1},
	address = {Heidelberg},
	abstract = {Previous work on Quality of Service in Cut-through networks shows that resource reservation mechanisms are only effective below the saturation point. Admission control in these networks will therefore need to keep network utilization below the saturation point, while still utilising the network resources to the maximum extent possible. In this paper we propose and evaluate three admission control schemes. Two of these use a centralised bandwidth broker, while the third is a distributed measurement based approach. We combine these admission control schemes with a DiffServ based QoS scheme for virtual cut-through networks to achieve class based bandwidth and latency guarantees. Our simulations show that the measurement based approach favoured in the Internet communities performs poorly in cut-through networks. Furthermore it demonstrates that detailed knowledge on link utilization improves performance significantly.},
	author = {Reinemo, Sven-Arne and Frank Olaf {Sem-Jacobsen} and Skeie, Tor and Lysne, Olav},
	editor = {Timothy Mark {Pinkston} and Viktor K. {Prasanna}}
}
