A graph is just a bunch of points with lines between some of them, like a map of cities linked by roads. A rather simple notion. Nevertheless, the theory of graphs has broad and important applications, because so many things can be modeled by graphs. For example, planar graphs — graphs in which none of the lines cross are— important in designing computer chips and other electronic circuits. Also, various puzzles and games are solved easily if a little graph theory is applied.

A Theory of Graphs

Resilience-driven restoration model for interdependent infrastructure networks

Critical interdependent infrastructure networks such as water distribution, natural gas pipeline, electricity power, communication and transportation systems provide the essential necessities for societies and their utilization is the backbone of everyday processes such as production, health, convenience and many more. Often cascading dysfunctionality or disruption in these critical infrastructure networks triggers chain reactions of blackouts or blockages through the system of highly interconnected infrastructure networks, and the disruption of surrounding societies. For the planning of restoration processes and resilience of these, social aspects and demographics should also be considered to assign and mitigate the possible social risks associated with these disruptions. In this work, we study the restoration planning of critical interdependent infrastructure networks after a possible disruptive event by mainly emphasizing on the vulnerability indices of interacting society. We integrate (i) a resilience-driven multi-objective mixed-integer programming formulation to schedule the restoration process of disrupted network components in each network with (ii) an index of social vulnerability that is geographically distributed. We present an illustrative example of the proposed integrated model that focuses on studying the community resilience in Shelby County, TN, United States.

Community resilience-driven restoration model for interdependent infrastructure networks

The decoupled architecture and the fine-grained flow-control feature limit the scalability of a flow-based software-defined network (SDN). In order to address this problem, some studies construct a flat control plane architecture; others build a hierarchical control plane architecture to improve the scalability of an SDN. However, the two kinds of structure still have unresolved issues: A flat control plane structure cannot solve the superlinear computational complexity growth of the control plane when the SDN scales to a large size, and the centralized abstracted hierarchical control plane structure brings a path stretch problem. To address these two issues, we propose Orion, a hybrid hierarchical control plane for large-scale networks. Orion can effectively reduce the computational complexity of an SDN control plane by several orders of magnitude. We also design an abstracted hierarchical routing method to solve the path stretch problem. Furthermore, we propose a hierarchical fast reroute method to illustrate how to achieve fast rerouting in the proposed hybrid hierarchical control plane. Orion is implemented to verify the feasibility of the hybrid hierarchical approach. Finally, we verify the effectiveness of Orion from both the theoretical and experimental aspects.

A Hybrid Hierarchical Control Plane for Flow-Based Large-Scale Software-Defined Networks

Network and service management encompasses a set of activities, methods, procedures, and tools, whose ultimate goal is to guarantee the proper functioning of a networked system. Computational tools are essential to help network administrators in their daily tasks, and information visualization techniques are of great value in such context. In essence, information visualization techniques associated to visual analytics aim at facilitating the tasks of network administrators in the process of monitoring and maintaining the network health. This paper surveys the use of information visualization techniques as a tool to support the network and service management process. Through a systematic literature review (SLR), we provide a historical overview and discuss the current state of the art in the field. We present a classification of 285 articles and papers from 1985 to 2013, according to an information visualization taxonomy, as well as a network and service management taxonomy. Finally, we point out future research directions and opportunities regarding the use of information visualization in network and service management.

A Survey on Information Visualization for Network and Service Management

This paper proposes an IP fast rerouting method which can be implemented in OpenFlow framework. While the current IP is robust, its reactive and global rerouting processes require the long recovery time against failure. On the other hand, IP fast rerouting provides a milliseconds-order recovery time by proactive and local restoration mechanism. Implementation of IP fast rerouting is not common in real systems, however; it requires the coordination of additional forwarding functions to a commercial hardware. We propose an IP fast rerouting mechanism using OpenFlow that separates control function from hardware implementation. Our mechanism does not require any extension of current forwarding hardware. On the contrary, increase of backup routes becomes main overhead of our proposal. We also embed the compression mechanism to our IP fast rerouting mechanism. We show the effectiveness of our IP fast rerouting in terms of the fast restoration and the backup routes compression effect through computer simulations. key words: flow table compression, implementation, IP fast rerouting, OpenFlow, restoration

Autonomous IP Fast Rerouting with Compressed Backup Flow Entries Using OpenFlow

IP Fast Reroute techniques have been proposed for achieving fast failure recovery in just a few milliseconds. The basic idea of IP Fast Reroute is to reduce recovery time after failure by precomputing backup routes. A multiple routing configurations (MRC) algorithm has been proposed for obtaining IP Fast Reroute. MRC prepares backup configurations, which are used for finding a detour route after failure. On the other hand, requiring too many backup configurations consumes more network resources. It is necessary to recover more traffic flows with fewer backup configurations to ensure scalability. We propose a new backup configuration-creation algorithm for maximizing traffic flows which are fast recovered as much as possible under a limited number of backup configurations. The basic idea is to construct a spanning tree excluding failure links with higher link-loads in each backup configuration. We show that our algorithm has more robust on actual large IP networks.

Minimum Backup Configuration-Creation Method for IP Fast Reroute

Disaster Recovery for Transport Network through Multiple Restoration Stages

IP Fast Reroute techniques have been proposed to achieve fast failure recovery in just a few milliseconds. The basic idea of IP Fast Reroute is to reduce recovery time after failure by precomputing backup routes. A multiple routing configurations (MRC) algorithm has been proposed for obtaining IP Fast Reroute. MRC prepares backup configurations, which are used for finding a detour route after failures. However, this current algorithm requires too many backup configurations to recover from failures. We propose a new backup configuration computation algorithm for reducing configurations as much as possible. The basic idea is to construct a spanning tree excluding failure links in each backup configuration. We show that the effectiveness of our algorithm is especially high in large-scale power-law networks.

Scalable backup configurations creation for IP fast reroute

We designed and developed the first proto-type system of adaptive virtual network topology control based on an SDTN architecture for robust network virtualization. Dynamic resource optimization among multiple virtual networks based on measured traffic was successfully demonstrated on testbed network.

Shohei Kamamura

Papers

Autonomous IP Fast Rerouting with Compressed Backup Flow Entries Using OpenFlow

Minimum Backup Configuration-Creation Method for IP Fast Reroute

Disaster Recovery for Transport Network through Multiple Restoration Stages

Scalable backup configurations creation for IP fast reroute

Experimental demonstration of adaptive virtual network topology control mechanism based on SDTN architecture