Computer Engineering

All-optical networks with wavelength division multiplexing capability are the promising candidates for the next generation Internet. As these networks carry enormous bandwidth, it is not optional for them to be survivable. Although the available proactive restoration schemes provide 100% restoration guarantee, they require a huge extra capacity and usually result in an extremely high blocking probability. In this paper, we propose a novel active scheme that uses multiple predefined but not reserved backup paths along a working path to restore the lightpath in the event of link-failure. Simulation results based on two typical networks indicate that our new restoration method can reduce blocking probability and capacity requirement significantly while guaranteeing a very high restoration probability.

The increasing demand for bandwidth that has resulted from the emergence of various bandwidth-thirsty applications has increased the need for employing WDM as a dominant technology for the next-generation optical internet. As these networks carry gigantic amounts of information, survivability has become a primary and basic need for them. Although the available proactive protection schemes provide a 100% restoration guarantee, they require huge redundancy and usually result in a very high blocking probability. We propose a novel active restoration scheme that restores a failed primary lightpath based on multiple predefined but nonreserved backup paths along the primary path. Extensive simulation results based on three typical test networks indicate that with a small increase in restoration time, our new restoration scheme can reduce the blocking probability and the capacity requirement significantly while guaranteeing a very high restoration probability.

Optical Burst Switching (OBS) has been proposed as a new paradigm to achieving a practical balance between Optical Circuit Switching (OCS) and Optical Packet Switching (OPS). Hybrid Optical Networks (HON) that combines OCS and OBS has emerged to grant the OBS network the ability to support connection-oriented applications. Although efficient in terms of reducing the burst loss probability as well as improving the overall network performance, it provides a limited degree of Quality of Service (QoS). What we mean by QoS is the capability of a network to provide a guaranteed level of availability while satisfying strict limits on delay. In this paper, we propose new hybrid architecture for OBS networks. The proposed architecture qualifies the OBS network to support different classes of QoS.

Active restoration (AR) is a novel lightpath restoration scheme proposed to guarantee a certain degree of survivability in WDM optical networks with a reasonable tradeoff between capacity requirement and restoration time. An analytical model has been proposed to analyze the restoration probability behavior of a connection request in optical networks employing AR based on the assumption that all the backup routes of the connection are independent. In a real AR-based optical network, however, the backup routes of a connection are likely to be correlated since they may share some common links along their routes. Therefore, an analytical approach was proposed to model the restoration probability of the connection by considering all the possible correlation between any two of its successive backup routes. Although the proposed approach achieves better approximation to the restoration probability, it overestimates the restoration probability of the connection when its non-successive backup routes are being correlated. However, considering all the possible correlations among backup routes is computationally intractable. In this paper, we conduct a comprehensive performance analysis for AR-based optical networks. In particular, we propose a novel analytical framework for modelling the restoration probability of a connection when the possible correlations among any three successive backup routes are fully incorporated

The ever-increasing demand for network bandwidth makes network survivability an issue of great concern. Lightpath restoration is a valuable approach to guaranteeing an acceptable level of survivability in WDM optical networks with better resource utilization than that of its protection counterpart. Active restoration (AR) is a newly proposed lightpath restoration scheme [M. Mostafa et al. OSA Journal of Optical Networking, vol. 3, no. 4, pp. 247–260] that combines the best of protection and reactive restoration while avoiding their shortcomings. In this paper, we conduct detailed performance analysis on the restoration probability of AR-based WDM networks. In particular, analytical models of restoration probability are developed respectively for networks with full-wavelength conversion capability and for networks without wavelength conversion capability under different backup path searching schemes. Based on the new models, we investigate the effects of wavelength availability, wavelength conversion capability, path length as well as backup path seeking methods on the restoration probability.

Active restoration (AR) is a novel lightpath restoration scheme proposed recently to guarantee a certain degree of survivability in wavelength-division multiplexing (WDM) optical networks with a reasonable trade-off between capacity requirement and restoration time. In this paper, we conduct a comprehensive performance analysis for AR-based optical networks. In particular, we propose a novel analytical framework for modeling the restoration probability of a connection (the probability that the connection can be successfully restored in case of a failure) when the possible correlation among its multiple backup routes is incorporated. Although theoretically, we need to consider all the possible correlations between as many as N 2 À Á pairs of backup routes to analyze the restoration probability in a network with N nodes, and this high computation complexity may obscure the practicality of an approach, considering all the possible correlations among backup routes, our analysis in this paper indicates that by considering at most the possible correlations among any three successive backup routes of a connection, we can achieve a very good approximation to the simulated restoration probability of the connection, as verified by extensive simulation results upon two typical network topologies under various workloads. We find that the proposed framework can deeply investigate into the inherent relationship among restoration probability, wavelength channel utilization ratio, number of wavelengths per fiber, routes hop length, and wavelength conversion capability. As a result, the framework significantly contributes to the related areas by providing network designers with a quantitative tool to evaluate the restoration probability and, thus, the survivability of AR-based optical networks.

Dedicated protection and shared protection are the main protection schemes in optical wavelength division multiplexing (WDM) networks. Shared protection techniques surpass the dedicated protection techniques by providing the same level of availability as dedicated protection with reduced spare capacity. Satisfying the service availability levels defined by the user's service-level agreement (SLA) in a cost-effective and resource-efficient way is a major challenge for networks operators. Hence, evaluating the availability of the shared protection scheme has a great interest. We recently developed an analytical model to estimate network availability of a WDM network with shared-link connections under multiple link-failures. However, this model requires the information of all possible combinations of the unshared protection paths, which is somehow troublesome. In this paper, we propose a more practical analytical model for evaluating the availability of a WDM network with shared-link connections under multiple link-failures. The proposed model requires only an estimate of the set of shared paths of each protection path. The estimated availability of the proposed model accurately matched with that of the previous model. Finally, we compare the previous model with the proposed model to demonstrate the merits and demerits of both models illustrating the threshold at which each model performs better based on the computational complexity. The proposed model significantly contributes to the related areas by providing network operators with a practical tool to evaluate quantitatively the system-availability and, thus, the expected survivability degree of WDM optical networks with shared connections under multiple-link failures.

In optical Wavelength Division Multiplexing (WDM) networks, different protection schemes have been proposed in the literature, namely, dedicated protection and shared protection. Shared protection techniques significantly reduce the required spare capacity by providing the same level of availability as dedicated protection. However, current mission critical applications (which heavily depend on the availability of communication resources) require connection availability in the order of 99.999% or higher, which corresponds to a downtime of almost 5 min a year on the average. Therefore, in order to satisfy a connection serviceavailability requirement defined by the users Service Level Agreement in a cost-effective and resource-efficient way, network operators need a systematic mechanism to evaluate the network availability under multiple failure scenario to ensure that current network configuration can meet the required availability degree; otherwise, a network upgrade is required. Unfortunately, under multiple failure scenario, traditional availability analysis techniques based on reliability block diagrams are not suitable for survivable networks with shared spare capacity. Therefore, a new concept is proposed to facilitate the calculations of network availability. In this paper, we propose an analytical model for evaluating the availability of a WDM network with shared-link connections under multiple link failures. The analytical model is

Evaluation of availability and unavailability of optical connections is necessary for WDM optical networks to make efficient use of optical resources. The design of a protection scheme that improves the availability of high priority optical connections is a major challenge faced by optical network operators. This paper deals with the general protection scheme in WDM optical networks and it provides the mathematical formulation to evaluate the availability/unavailability of protected optical connections. General link failure scenarios are taken into account considering that a link failure affects all the optical connections routed on that link. We have performed some numerical tests and their results are presented to investigate the availability and unavailability degrees for different number of protections.

Will-beset by IN -TECH resulting in network holes, cuts (partitions) or even breakdown of the overall network connectivity as shown in Fig. 1. Therefore, it is essential to assess the vulnerabilities of mission critical networks to such region-failures. Some research has been conducted to understand the impact of region failures on wired backbone networks such as [11-18]. On the other hand, the cut detection problem has been investigated by [19] and [20].

Will-beset by IN -TECH resulting in network holes, cuts (partitions) or even breakdown of the overall network connectivity as shown in Fig. 1. Therefore, it is essential to assess the vulnerabilities of mission critical networks to such region-failures. Some research has been conducted to understand the impact of region failures on wired backbone networks such as [11-18]. On the other hand, the cut detection problem has been investigated by [19] and [20].

Will-beset by IN -TECH resulting in network holes, cuts (partitions) or even breakdown of the overall network connectivity as shown in Fig. 1. Therefore, it is essential to assess the vulnerabilities of mission critical networks to such region-failures. Some research has been conducted to understand the impact of region failures on wired backbone networks such as [11-18]. On the other hand, the cut detection problem has been investigated by [19] and [20].

Evaluation of availability and unavailability of optical connections is necessary for WDM optical networks to make efficient use of optical resources. The design of a protection scheme that improves the availability of high priority optical connections is a major challenge faced by optical network operators. This paper deals with the general protection scheme in WDM optical networks and it provides the mathematical formulation to evaluate the availability/unavailability of protected optical connections. General link failure scenarios are taken into account considering that a link failure affects all the optical connections routed on that link. We have performed some numerical tests and their results are presented to investigate the availability and unavailability degrees for different number of protections.

The Internet explosion and the increase in crucial web applications such as ebanking and e-commerce, make essential the need for network security tools. One of such tools is an Intrusion detection system which can be classified based on detection approachs as being signature-based or anomaly-based. Even though intrusion detection systems are well defined, their cooperation with each other to detect attacks needs to be addressed. Consequently, a new architecture that allows them to cooperate in detecting attacks is proposed. The architecture uses Software Agents to provide scalability and distributability. It works in two modes: learning and detection. During learning mode, it generates a profile for each individual system using a fuzzy data mining algorithm. During detection mode, each system uses the FuzzyJess to match network traffic against its profile. The architecture was tested against a standard data set produced by MIT's Lincoln Laboratory and the primary results show its efficiency and capability to detect attacks. Finally, two new methods, the memory-window and memoryless-window, were developed for extracting useful parameters from raw packets. The parameters are used as detection metrics.

Recently, Wireless Sensor Networks (WSNs) have been deployed into a variety of applications including homeland security, military systems, and health care. Sensor nodes deployed in such networks are subject to several attacks such as sinkhole and select forwarding, wormhole, Hello flood, and replication attacks. Therefore, developing secure and energy-efficient routing protocols to protect WSNs against these attacks while efficiently utilizing the energy of the deployed nodes has become imperative. Several routing protocols have been proposed in the literature for WSNs. Most of these protocols assume static nodes and sinks to collect data from network fields. However, they may be highly movable, and recent advances show that mobile sensors in WSNs have a promising performance. Therefore, this paper surveys the state of the art on routing protocols related to WSNs and presents the security issues or problems associated with the current protocols as well as discusses the future trends...

This paper introduces a new secure hybrid payment system in KSA that enables people to pay their bills, recharge their mobiles, as well as transfer balance using secure SMS messages. The proposed system implements a flexible and scalable architecture that has three main components: Customer, bank, and provider. The system is called hybrid because it combines two transmission media, SMS messages and the Internet. The SMS messages are used between the customer and the bank components while the Internet is used between the bank and provider components. Also the SMS messages can be used between the provider and the customer components. When a customer gets notified about his/her bill, he/she makes a payment request to the bank through a secure SMS message. The system supports both prepaid and post-paid payments. In prepaid, customers initiate payment requests with the desired amount while in post-paid, customers respond for payment notifications. Unlike current SMS-based mobile payment systems in which mobile operators are involved in transactions as a payment gateway, our system provides end-to-end secure transaction. Accordingly, the proposed system provides algorithms for key generation and distribution, confidentiality, integrity, authentication, non-repudiation, and protection against replay attacks. To complete the system, an android application called PayingSMS is developed to enable customers make their payment requests in an easy and secure environment. Finally, the security analysis of the proposed system is discussed.