Shahram Shah Heydari

Network survivability in large-scale regional failure scenarios

In this short paper we present a preliminary study of the impact of large-scale failures on communication networks. Models for study of large-scale failures are studied and unique characteristics of these scenarios as well as their differences with independent multiple-failure scenarios are presented. In particular, we focus on regional large-scale failure scenarios in which node/link failures are location-dependent. Methods for restoration of traffic and the issue of failure notification time are examined. The regional failure scenario is examined on a sample backbone European network and the simulation results including network capacity requirements and failure notification times for various cases are analyzed and discussed.

Enhancing network service survivability in large-scale failure scenarios

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

Optimization of SDN Flow Operations in Multi-Failure Restoration Scenarios

Flexible network configuration in software-defined networks makes it possible to dynamically restore flows. To this end, network devices carry out flow operations (i.e., adding or removing flow-entries to/from the flow-tables) to re-route the disrupted flows. Current flow restoration techniques do not consider the number of operations, and hence, are inefficient in disaster scenarios. We aim to minimize the number of operations in such cases and formulate integer programs to find a path: 1) with the lowest path cost requiring up to a given number of operations; 2) requiring the fewest possible operations; and 3) with a Dijkstra-like path cost requiring minimum operations. We study the tradeoff between path cost and the number of operations and prove that the second and third problems are polynomial-time solvable. We propose optimal/suboptimal algorithms with Dijkstra-like complexity that find nearly-optimal solutions. The simulation results show that our methods reduce the number of operations up to 50%, and the best performance is achieved when the number of failed links is small.

A self-healing approach for LTE Evolved Packet Core

The 3GPP Long Term Evolution (LTE) is considered as a dominant future cellular wireless technology in terms of performance and user experience. With technological advancement of wireless networks, dependencies and business impact of mobile network services have also been increased phenomenally. It is, therefore, crucial to address issues regarding network infrastructure or service failure. In this paper, a self-healing solution is presented for LTE Evolved Packet Core (EPC) with a view to maintaining service continuity in the event of network elements failures. Restoration mechanism and associate operational procedures with regards to service survivability are described in details. Simulation results are provided and the results demonstrate potential of this approach.

OLSR-based Topology Discovery for Mobile Situational Awareness Systems

Abstract In this paper, we propose a non-intrusive approach for connectivity visualization of OLSR-based MANET topology based on local topology databases available in an OLSR node. Two different scenarios are considered: a central (full view) topology from a command and control location, or a nodal (partial) view from an ad-hoc node. A simulation based analysis is conducted to calculate total number of active links at a particular time in full and nodal topology views. Also the error rate of network topology discovery based on total undiscovered link both mobile and static scenario is considered and reported in this paper.

Multi-failure restoration with minimal flow operations in software defined networks

We consider dynamic flow restoration in multi-failure scenarios in OpenFlow-based Software-Defined Networks (SDNs). Flexibility of network configuration in these networks makes it possible to dynamically restore flows in case of multilink failures. To re-route the failed flows, network devices such as switches carry out flow operations, i.e., add new flow-entries to the flow-tables. In disaster scenarios where thousands of flows must be restored in a short time, the time required to perform such operations is significant and must be minimized to maintain a carrier-grade network. Shortest-path based techniques do not take into account the number of flow operations (namely, operation cost) and therefore are inefficient for disaster scenarios. We incorporate the operation cost into the flow restoration problem, and formulate the problem of finding a path 1) with the lowest path cost with capped operation cost, 2) with the lowest possible operation cost, and 3) with the minimum operation cost amongst all the paths with a Dijkstra-like path cost. We propose optimal algorithms with Dijkstra-like complexity for the second and third problems. The simulation results with European Reference Network (ERnet) show that our proposed methods on average can reduce the number of required flow operations up to 15% while the path cost rises less than 3%.

Topology-based Proactive Network Protection in Large-scale Failure Scenarios☆

Abstract Natural disasters are among the main causes of large-scale failure scenarios. The dynamic behaviour of natural disasters and their probabilistic failure pattern indicates a need for a dynamic probabilistic protection approach to address the issue and reduce the number of disrupted connections in the network. Appropriate data protection against a time-varying destructive phenomenon serves to prevent damage before it occurs. In this case, the endangered route should be detected and the data passing through should be rerouted through more reliable paths prior to failure. The high-risk paths can be detected based on the decision parameters in the dynamic preventive approach. In this article, we develop a new method to improve the assignment procedure of decision factors in preventive protection models using network topological properties and links failure probability. The proposed decision parameters are adaptive with the network conditions and updateable while the disaster spreads through the region. The adaptive characteristic of the rerouting decision parameter will enhance network efficiency and facilitate network management.

Performance evaluation of LTE EPC self-healing solutions

The Long Term Evolution (LTE) defined by 3rdGeneration Partnership Project (3GPP) is a dominant cellular wireless technology which is currently being commercialized worldwide. In this paper, we evaluate the performance of self-healing schemes for LTE Evolved Packet Core (EPC) network elements failures in different architectural configurations. We also analyze message overhead and bandwidth requirements for the signaling traffic incurred by this design and its ramification to LTE core network. The simulation experiments are conducted to evaluate the performance of the self-healing schemes.

Analyzing network failures in disaster scenarios using a travelling wave probabilistic model

Communication network infrastructures are always in danger of natural disasters or physical attacks. The destructive effects of these incidents can cause large-scale failures in the network. This paper proposes a model for the impact of failure considering wave energy behaviour to compute probability of failures, and calculates required spare capacities in path restoration mechanism based on this model and compares it with the deterministic model. The proposed model can be employed to identify additional resources to provide the expected level of survivability in the event of large-scale failure scenarios.

Design and Implementation of a Software-Defined Integrated Wired-Wireless Network Testbed

Software-Defined Networking (SDN) has been gaining momentum as the main technology for implementation of data center environment, and its usage has recently been extended to transport and wireless networks. Recently, research has been conducted on applying SDN principals to 802.11 networks in order to solve traditional issues such as handover, Radio Resource Management (RRM), network security, as well as integration of wired and 802.11 networks. This paper presents a design for the integration of 802.11 access points into an SDN test bed as an experimental environment to perform analysis, development and testing of SDN applications in 802.11 networks. We present design challenges and solutions, and performance results obtained from this testbed.