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EN
A spectrum defragmentation problem in elastic optical networks was considered under the assumption that all connections can be realized in switching nodes. But this assumption is true only when the switching fabric has appropriate combinatorial properties. In this paper, we consider a defragmentation problem in one architecture of wavelength-space-wavelength switching fabrics. First, we discuss the requirements for this switching fabric, below which defragmentation does not always end with success. Then, we propose defragmentation algorithms and evaluate them by simulation. The results show that proposed algorithms can increase the number of connections realized in the switching fabric and reduce the loss probability.
EN
This article presents a new recurrent method for modelling multi-service switching networks with overflow links. In the proposed method, the blocking probability for a given stage of the switching network is determined on the basis of the characteristics of the preceding stage. A particular attention is given to a possibility of a considerable reduction of the internal blocking probability of the switching network that would result from an application of additional overflow links between neighbouring switches of the first stage of the network. The results of the analytical modelling of selected multi-service switching networks with overflow links in the first stage are compared with the results of the simulation experiments. The study confirms the accuracy of all the adopted theoretical assumptions in the proposed analytical model of the multi-service switching network.
3
Content available remote Multi-service switching networks with overflow links
EN
The article presents the results of a simulation study on multirate three-stage Clos switching networks with additional inter-section links. Switching networks in which a system of overflow links was provided for the first, second and the third stage are investigated. Additionally, different structures of connections between inter-section links are discussed. The investigation has proved that an application of overflow systems is followed by a substantial decrease in the internal blocking probability in the switching network. An appropriate capacity of overflow links can even result in a virtually complete elimination of internal blocking. The article proves that the best results are obtained with the introduction of overflow links to the first stage of the network, both in the case of point-to-point and point-to-group selection.
4
EN
A new control algorithm for log2(N, 0, p) switching networks composed of 2x2 switching elements has been proposed recently. Under this algorithm. log2(N,O, p) switching networks with even number of stages are wide-sense nonblocking (WSNB) if p is the same as for the rearrangeable nonblocking (RNB) one. In this paper we extend this solution to logd(N,0,p) switching networks. The control algorithm is appropriately modified to switching networks composed of dxd switches. Wide-sense nonblocking operation of such switching networks with even number of stages is proved. We showed lhat number of planes needed for WSNB operation is also the same as in RNB switching networks.
EN
This paper presents three approximate calculation methods of occupancy distribution and blocking probability in switching networks which are offered multi-service traffic streams generated by Binomial (Engset) & Poisson (Erlang) & Pascal traffic sources. The proposed methods belong to the class of methods known as the effective availability methods. The basis of the proposed calculation algorithms is the occupancy distribution in interstage links as well as in the outgoing links (forming outgoing directions). These distributions are calculated with the help of the full-availability group model and the limited-availability group model. The results of analytical calculations of the blocking probabilities are compared with the simulation results of three-stage switching networks, and, therefore, the validity of the assumptions used in the model is proved.
EN
In this paper an approximate method of blocking probability calculation in multi-service switching networks carrying a mixture of different multi-rate unicast and multicast traffic streams is presented. Three algorithms of setting up multicast connections arę considered and discussed. Special attention is paid to the methods for determining the effective availability parameter for multicast connections. The results of the analytical calculations of the blocking probability are compared with the data of the discrete event simulations of the switching networks.
PL
W artykule zaprezentowano przybliżoną metodę obliczania prawdopodobieństwa blokowania w wielousługowych sieciach przenoszących mieszaninę różnych strumieni ruchu jednopołączeniowego i rozgłoszeniowego (multicast). Artykuł rozważa trzy algorytmy nawiązywania połączeń typu multicast. Szczególną uwagę zwrócono na metody określające parametry efektywnej dostępności dla połączeń typu multicast. Wyniki analitycznych obliczeń prawdopodobieństwa blokowania porównano z wynikami symulacji sieci przełącznikowych.
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