Daniel Orincsay

Accurate Traffic Classification

The analysis of network traffic can provide important information for network operators and administrators. One of the main purposes of traffic analysis is to identify the traffic mixture the network carries. A couple of different approaches have been proposed in the literature, but none of them performs well for all different application traffic types present in the Internet. Thus, a combined method that includes the advantages of different approaches is needed, in order to provide a high level of classification completeness and accuracy. According to our best knowledge, this study is the first attempt where the currently known traffic classification methods are benchmarked on network traces captured in operational mobile networks. The pros and cons of the classification methods are analyzed, based on the experienced accuracy for different types of applications. Using the gained knowledge about the strengths and weaknesses of the existing approaches, a novel traffic classification method is proposed. The novel method is based on a complex decision mechanism, in order to provide an appropriate identification mode for each different application type. As a consequence, the ratio of the unclassified traffic becomes significantly lower. Further, the reliability of the classification improves, as the various methods validate the results of each other. The novel method is tested on several network traces, and it is shown that the proposed solution improves both the completeness and the accuracy of the traffic classification, when compared to existing methods.

On the validation of traffic classification algorithms

Detailed knowledge of the traffic mixture is essential for network operators and administrators, as it is a key input for numerous network management activities. Traffic classification aims at identifying the traffic mixture in the network. Several different classification approaches can be found in the literature. However, the validation of these methods is weak and ad hoc, because neither a reliable and widely accepted validation technique nor reference packet traces with well-defined content are available. In this paper, a novel validation method is proposed for characterizing the accuracy and completeness of traffic classification algorithms. The main advantages of the new method are that it is based on realistic traffic mixtures, and it enables a highly automated and reliable validation of traffic classification. As a proof-of-concept, it is examined how a state-of-the-art traffic classification method performs for the most common application types.

Surviving multiple network failures using shared backup path protection

This paper studies the possibilities of protecting backbone networks from multiple simultaneous failures. Although methods that prepare the networks to survive single failures were extensively studied in the literature, in order to provide extra high availability for mission-critical applications, the possibility of more than one simultaneous failure has to be considered too. The general technique of protecting a traffic flow is to establish a backup path where the traffic is redirected when a failure occurs along its active path. Using this technique the total capacity reservation is at least doubled compared to the non-protected case. To avoid this large amount of bandwidth reservation by the backup paths, the shared backup path protection paradigm can be used, which is a promising scheme favored by the Internet engineering task force. In this paper the two backup path based protection scheme is introduced, which provides survivability against any two simultaneous failures. Further, a novel shared protection strategy is proposed that improves the failure tolerance of the traditional single backup path based protection. The performance of the different protection types is examined through simulations.

Multi-hour Design of Dynamically Reconfigurable MPLS Networks

This paper proposes an algorithm for cost-efficient network design. The two main network components are the routers and the links connecting them. As these network elements have discrete capacity values, their costs are modeled by stepwise functions. In the current interpretation of the network design problem the subproblems of topological design, resource dimensioning, and routing of traffic flows are handled simultaneously. Using new network technologies (e.g., MPLS) the operators have the opportunity to reconfigure their networks dynamically. By using this function the periodic (e.g., daily, weekly) changes of traffic volumes and directions can be taken into consideration during network design resulting in lower deployment costs. The algorithm proposed for multi-hour design is based on an efficient, published method. The efficiency of the new algorithm is demonstrated by simulation on random and real network topologies with the help of two reference algorithms.

Prompt partial path optimization in MPLS networks

In this paper we evaluate approaches that allow the re-routing of a set of already established label switched paths (LSPs) in multiprotocol label switching (MPLS) networks when a new LSP demand faces constrained shortest path first failure. Two optimization algorithms are proposed: one is based on an integer linear programming formulation of the problem, while the other one is a heuristic method based on Dijkstras shortest path first algorithm: We analyze the efficiency of our algorithms in a dynamic network environment. The simulation experiments show that our method significantly increases the total network throughput. We also investigate the limitations of the applicability of proposed methods considering their running time.

Design of survivable VPN based VoIP networks

This paper addresses the issue of survivable voice over IP (VoIP) network design. In the applied model the whole VoIP network is divided into two logical components: the access network and the transport network. The access network consists of VoIP end-points, which connect to the transport network through edge routers serving as gateways. Thus, one task of the design process is to assign gateways to the VoIP end-points. To assure security and availability for the VoIP traffic, a virtual private network (VPN) is assumed as transport network in this paper; therefore, the other task is to specify the transport VPN in the most economical way, while also taking the possible failures of transport network elements into consideration. Assuming a single failure at a time, the survivability of the VoIP network can be assured by assigning two gateways, namely a primary and a backup one, to each VoIP end-point, and calculating two disjoint paths between each pair of gateways. The two tasks of survivable VoIP network design can be solved separately; however, in this paper, a novel solution is proposed in which the edge router assignment process takes both the objective function of VPN specification and the issues of survivability into consideration. Multiple methods realizing the novel approach are presented, which are based on the paradigms of evolutionary algorithms and simulated annealing. The performance of the presented methods is evaluated with the help of simulations, using a well-known greedy algorithm as reference. It is shown that the proposed methods outperform the reference algorithm significantly in the simulation scenarios investigated.

Cost-optimal design of VoIP networks using the VPN concept

This paper addresses the issue of cost-optimal voice over IP (VoIP) network design. In the applied model, the whole VoIP network is divided into two logical components: the access network and the transport network. The access network consists of VoIP end-points that connect to the transport network through edge routers serving as gateways. Since multiple edge routers may be available for any given VoIP node, one task of the design process is to assign a particular edge router to every VoIP node. The edge routers have to be connected in a way that security and availability can be assured for the VoIP traffic. One obvious approach to fulfilling these requirements, which is assumed throughout the paper, is to define a virtual private network (VPN). Supposing a large volume of VoIP traffic, the cost of the VPN can be significant; thus, the other task of VoIP network design is to specify the transport VPN in the most economical way. These two tasks of VoIP network design can be solved separately using existing methods; nevertheless, the specification of VoIP regions influences the cost of the final solution to a great extent. Therefore, in this paper a novel approach is proposed in which the edge router assignment process takes the objective function of VPN specification into consideration as well. In order to realize the new approach, multiple methods are introduced which are based on the paradigms of genetic algorithms and simulated annealing. These methods perform a sophisticated optimization of the gateway assignments using various cost calculation methods. To evaluate the new algorithms, a method based on a well-known greedy solution to the problem is used as reference. Moreover, a VPN specification algorithm is presented which utilizes the stepwise nature of the cost functions. The performance of the presented methods is evaluated with the help of simulations. It is shown that the proposed methods outperform the reference algorithm significantly in the simulation scenarios investigated.

Cost-optimal VPN based VoIP network design

This work addresses the design of cost-optimal VoIP networks. In our model the whole VoIP network is divided into two logical components: the access network and the transport network. The access network consists of the VoIP end-points that connect to the transport network through edge routers serving as gateways. Since more edge routers may be available for a given VoIP node, one task of the design process is to assign a particular edge router to every VoIP node. The edge routers have to be connected in such a way that security and availability can be assured for the VoIP traffic. One obvious approach to fulfilling these requirements is to define a VPN, which is assumed throughout the paper. Supposing large volume of VoIP traffic the cost of the VPN can be significant. Thus the other task of VoIP network design is to specify the transport VPN in the most economical way. These two tasks of VoIP network design can be solved separately using existing methods. Nevertheless, the VoIP region specification influences the cost of the final solution to a great extent. Therefore, in This work we propose a novel solution in which the edge router assignment takes the objective function of VPN specification into consideration. Moreover, a numerical analysis is provided with the help of simulations.

On the use of EKB routing strategy in PNNI networks

The PNNI protocol generally applied in ATM networks provides a powerful background to use smart traffic engineering methods. Aiming at increasing the probability of successful call setup as well as restoration after failure more paths can be precalculated and stored for each destination in switches. In our previous work a novel route calculation strategy called EKB was introduced, based on the algorithm of Edmonds and Karp, which addresses the reduction of restoration time in case of failure. The behavior of EKB was examined for failure situations focusing on permanent connections. In this study we extend the analysis of EKB by applying dynamic simulation scenarios where, beside permanent connections, switched connections are also considered. Thus, a reliable picture can be obtained about the performance of the novel algorithm EKB for normal operation.