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1
Content available Spectrum Allocation Policy in Elastic Optical Networks
Olszewski I.
International Journal of Electronics and Telecommunications
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2017
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Vol. 63, No. 4
423--429
EN
The considered problem covers routing and spectrum allocation problem (RSA problem) in Elastic Optical Networks while maintaining the spectrum continuity constraints, non-overlapping spectra constraints for adjacent connections on individual links of the network and spectrum contiguity constraints of the connection. In this article the modified version of the First Fit spectrum slot allocation policy for Fixed Alternate Routing in flexible optical networks has been proposed. The Fixed Alternate Routing with proposed spectrum allocation policy rejects fewer requests, provides less bandwidth blocking probability and less spectrum fragmentation than Fixed Alternate Routing with well-known First Fit and Exact Fit spectrum allocation policies. However, the cost of improving these parameters is a higher computational complexity of the proposed allocation policy.
2
Content available remote Routing and Spectrum Assignment for Constant Bit Rate Connections in Spectrum Sliced Elastic Optical Path Networks
Olszewski I.
Przegląd Elektrotechniczny
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2015
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R. 91, nr 7
124-128
EN
In this paper a heuristic algorithm for finding an optical path in elastic optical path networks is proposed. The proposed algorithm for connection requests finds a spectrum required from an aggregated spectrum of the path belonging to a set of shortest paths measured by the number of links. It has been shown that the proposed algorithm rejects definitely fewer connection requests than the well-known algorithms solving the same problem.
PL
W pracy zaproponowano heurystyczny algorytm wyboru ścieżek w elastycznych sieciach optycznych. Zaproponowany algorytm zajmuje dla napływającego żądania wymagane pasmo w zagregowanym widmie ścieżki, należącej do zbioru najkrótszych ścieżek mierzonych liczbą łączy. W pracy wykazano, że algorytm ten odrzuca mniejszą liczbę żądań niż znane algorytmy minimalizujące rzeczywistą długość ścieżki.
3
Content available Dynamic RSA Problem for Time-Varying Traffic in Spectrum Sliced Elastic Optical Path Network
Olszewski I.
International Journal of Electronics and Telecommunications
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2015
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Vol. 61, No. 2
179-184
EN
Service time-varying traffic flexible optical networks require a dynamic bandwidth allocation in order to follow the source transmission rate. The problem of service time-varying traffic, assuming that the set of connection requests is not known in advance, is considered in this work. Connection requests arrive randomly and have random durations. The considered dynamic RSA problem involves minimizing the probability of future connections blocking while maintaining spectrum continuity constraints and non-overlapping spectrum assignment constraints between spectrum-adjacent connections on the network links. The proposed algorithm determines the path with the required number of slots around the reference frequency for a connection request. An analysis of the network with time-varying traffic on the network connections was carried out on the basis of spectrum expansion/contraction schemes which allow to determine average blocking probability of the additional slot requests on these connections. The obtained results have been compared with those obtained by a well known algorithm that solves the dynamic RSA problem.
4
Content available remote RSA Problem for Varying Traffic in Flexible Optical Networks
Olszewski I
Image Processing & Communications
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2014
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Vol. 19, no. 1
35--44
EN
The problem of service time-varying traffic in flexible transparent optical networks, assuming that the incoming connections and their duration are not known in advance, is considered in this work. Time-varying traffic requires dynamic spectrum allocation for connections implemented in the network. In the considered problem, a path with the required spectrum around the reference frequency is determined for each incoming connection by the routing algorithm. In order to take into account the dynamic spectrum allocation for the connections in the network, two spectrum expansion/- contraction schemes have been applied on the basis of which the average blocking probability for the incoming request additional slot was determined.
5
Content available remote Algorithms of Routing and Spectrum Assignment in Spectrum Flexible Transparent Optical Networks
Olszewski I.
Przegląd Elektrotechniczny
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2013
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R. 89, nr 10
248-253
EN
The considered problem of routing and spectrum assignment (RSA) takes into consideration minimizing the length of the transmission distance under spectrum continuity constraints and the relationship between the traffic bitrates and the spectrum bandwidth. The proposed algorithms constitute modifications of the well-known Dijkstra's algorithm. The obtained results show that a significant reduction in the number of rejected requests can be achieved by an appropriate selection of the scheme spectrum segments in the aggregated spectrum of the path but not by increasing the computational complexity of the algorithms.
PL
Rozważany problem rutingu I przypisania widma (RSA) obejmuje minimalizację długości ścieżki transmisyjnej przy warunkach nałożonych na ciągłość widma oraz zależność pomiędzy szybkością binarną i widmem pasma sygnału. Zaproponowane algorytmy stanowią modyfikację algorytmu Dijkstry. Uzyskane wyniki pokazują, że istotna redukcja liczby odrzuconych żądań może być uzyskana nie poprzez zwiększanie złożoności obliczeniowej algorytmu, ale poprzez odpowiedni schemat wyboru segmentu widma z zagregowanego widma ścieżki.
6
Content available remote An algorithm of choosing LSPs in the MPLS network with unreliable links
Olszewski I.
Przegląd Elektrotechniczny
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2011
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R. 87, nr 2
285-290
EN
In this paper an algorithm for choosing LSPs in the MPLS network with unreliable links is proposed. The number of lost packets on the failed LSP depends on the restoration time of this LSP on the global backup path. In turn, the restoration time depends on the distance between the node which detected failure and the node responsible for traffic redirection from failed to global backup LSP. To reduce restoration time the distance between these nodes is decreased by length limitation of active LSP. The formulated problem covers limitation of the path length determined by the number of links and limitation of LSP failure probability. The algorithm solving the formulated problem of optimization gives a local solution for given limitations.
PL
W pracy zaproponowano algorytm wyboru ścieżek LSPs w sieciach IP/MPLS o zawodnej strukturze. Liczba utraconych pakietów na uszkodzonej ścieżce LSP zależy od czasu odtwarzania uszkodzonej ścieżki na ścieżce zabezpieczającej. Aby ograniczyć czas odtwarzania, odległość pomiędzy węzłami jest ograniczona poprzez ograniczenie długości ścieżki aktywnej. Rozważany problem obejmuje ograniczenie nałożone na długość ścieżki, mierzonej liczbą łączy oraz ograniczenie prawdopodobieństwa uszkodzenia ścieżki. Algorytm rozwiązujący sformułowany problem optymalizacji przy zadanych ograniczeniach wyznacza rozwiązanie lokalne
7
Content available A designing of telecommunication network for the bydgoszcz code area
Olszewski I.
Zeszyty Naukowe. Telekomunikacja i Elektronika / Uniwersytet Technologiczno-Przyrodniczy w Bydgoszczy
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2010
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z. 13
15--30
EN
In this paper an engineering approach to designing a telecommunication network over the Internet Protocol has been presented. The proposed network covers demand for telecommunication services in the Bydgoszcz code area operated by the Polish Telecommunications Co. In this network two classes of services were distinguished: Voice over the Internet Protocol (VoIP) and access to the Internet. The logical structure of the network is a superposition of two structures. First of them contains links that support VoIP and the second one contains links that provide access to the Internet. The physical structure of the network was implemented basing on the Synchronous Digital Hierarchy.
PL
W artykule przedstawiono inżynierskie podejście do projektowania sieci telekomunikacyjnej na platformie IP. Projektowana sieć pokrywa żądania na usługi telekomunikacyjne, w bydgoskiej strefie numeracyjnej, na obszarze której działa Telekomunikacja Polska (TP S.A.). W projektowanej sieci wyróżniono dwie klasy usług: telefonię internetową (VoIP) oraz dostęp do Internetu. Logiczna struktura sieci jest superpozycją dwóch struktur. Pierwsza z nich zawiera łącza, które realizują telefonię internetową oraz druga, która zapewnia dostęp do Internetu. Fizyczna struktura sieci została zaprojektowana w oparciu o Synchroniczną Hierarchię Cyfrową (SDH).
8
Content available remote The analytical modl of IP/MPLS network
Olszewski I.
Image Processing & Communications
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2009
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Vol. 14, no 4
63-71
EN
In this paper, the analysis of multi-servicing IP network with Multi-Protocol Label Switching (MPLS) protocol based on the proposed analytical and simulation models has been carried out. In the models two classes of service with different QoS parameters have been analyzed: class High, responsible for example for the Premium service, and class Low services for transmission of data. In this paper the changes of packet delays and lengths of queues for the given class of services in the network were taken into account, depending on the changes of average packet lengths, load of the network and the amount of inelastic traffic in the whole traffic. The results obtained in this paper have proved, that proposed analytical model is useful for analysis of the IP networks with MPLS protocol.
9
Content available remote On line routing of guaranteed bandwidth with restoration
Olszewski I.
Electronics and Telecommunications Quarterly
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2007
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Vol. 53, No 1
23-38
EN
In this paper the problem of finding a pair of link (node) disjoint active Label Switched Path (LSP) and backup LSP in Multi Protocol Label Switching (MPLS) networks is considered. It was assumed that capacity on the links of the backup Label Switched Paths can be shared. We focus on online algorithms for routing of guaranteed bandwidth of active LSPs and backup LSPs under partial information model in order to optimize the total amount of bandwidth consumed in the MPLS network. We consider only the case of protection against single link (node) failure. In this paper the comparison of two known routing algorithms was carried out. The first of them is based on Integer Linear Programming [3, 4] The second one is based on active-path-first heuristics [8]. In order to avoid the trap-problem the concept of Conflicting Link Set is used. Moreover, new algorithm based on active-path-first heuristics was proposed too. In this paper special attention has been paid to bandwidth consumed in the network, number of rejected connection set-up requests and running time of considered algorithms. The obtained results have proved that the proposed algorithm is comparable to the other algorithms but it has shorter running time then the existing ones.
10
Content available remote Algorytmy wyboru ścieżek LSP w sieciach MPLS
Olszewski I.
Kwartalnik Elektroniki i Telekomunikacji
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2004
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Vol. 50, z. 1
7-23
PL
W pracy przedstawiono algorytm wyboru ścieżek LSP w sieciach IP z protokołem MPLS. Pierwsza część zawiera wstęp, natomiast druga zarys wieloprotokołowej komutacji etykietowanej z uwzględnieniem zalet istotnych z punktu widzenia inżynierii ruchu. W części trzeciej przytoczono matematyczne sformułowanie problemu optymalizacji oraz heurystyczny algorytm rozwiązujący ten problem. W tej części pracy zaproponowano również nowy algorytm, będący ulepszoną wersją algorytmu publikowanego w literaturze, a także wyniki symulacyjne, uzyskane po zastosowaniu prezentowanych algorytmów. W ostatniej części pracy przedstawiono wnioski końcowe.
EN
In this paper the algorithms of choice of the LSP paths in the Multi-Protocol Label Switched (MPLS) network has been presented. In the first and second part the outline of this protocol has been pointed out. Especially the advantage of the traffic engineering has been taken. In the third part the mathematical optimization problem as well as the heuristic algorithm that solves this problem has been shown. In this part the new algorithm being the improved version of algorithm published in [4] has been proposed. Input data of the proposed algorithm are topological structure of the network and residual capacity of the links that connect the nodes of the network. For the pair of nodes the shortest path is chosen with respect to weights of links, which are function of residual capacity of these links. In the third part of the paper the simulation results has been shown. On the base of obtained results the analysis of algorithms in static and dynamic conditions were carried out. Obtained results prove, that the number of rejected LSP paths by the algorithm proposed in this paper are comparable with number of LSP paths rejected by the algorithm proposed in [4]. However the running time of proposed algorithms in much shorter and comparable with running time of the minimum hop algorithm. In the final part the conclusions has been drowed.
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