New structure for digital switching network

Methods for the design of cost-effective one-stage PCM switching networks composed of digital switching matrices are proposed. These one-stage networks have, in many cases, a more regular structure and contain fewer elements than networks currently known. The proposed one-stage networks can also be used as submodules for multistage networks.<>     

Cost-effective digital switching network

A method for the design of cost-effective one-stage PCM switching networks composed of uniform time-space elements is proposed. These one-stage networks can be used as submodules for multistage networks, having, in many cases, fewer elements than currently known networks.     

Reliable digital switching networks

A method for the design of economic and reliable PCM switching networks composed of uniform time-space elements is proposed. The described networks can be used in switching systems containing concentrators connected by an even number of PCM links to a main switching network.     

Semiconductor devices in photonic switching

Three types of photonic switching networks have been proposed, namely, optical space-division switching, optical wavelength-division switching. Optional function devices required for each switching network are as follows: optical switch matrix for space-division switching; optical memory and optical write/read gate for time-division switching; and tunable wavelength filter and wavelength converter for wavelength-division switching. Recent progress in semiconductor functional devices such as modulators, switching devices, bistable devices, and wavelength control devices, which would be key devices to build switching networks, is reviewed     

Software Defined Networking (SDN) controlled all optical switching networks with multi-dimensional switching architecture

Ultrahigh throughout capacity requirement is challenging the current optical switching nodes with the fast development of data center networks. Pbit/s level all optical switching networks need to be deployed soon, which will cause the high complexity of node architecture. How to control the future network and node equipment together will become a new problem. An enhanced Software Defined Networking (eSDN) control architecture is proposed in the paper, which consists of Provider NOX (P-NOX) and Node NOX (N-NOX). With the cooperation of P-NOX and N-NOX, the flexible control of the entire network can be achieved. All optical switching network testbed has been experimentally demonstrated with efficient control of enhanced Software Defined Networking (eSDN). Pbit/s level all optical switching nodes in the testbed are implemented based on multi-dimensional switching architecture, i.e. multi-level and multi-planar. Due to the space and cost limitation, each optical switching node is only equipped with four input line boxes and four output line boxes respectively. Experimental results are given to verify the performance of our proposed control and switching architecture.     

Acknowledgment-based broadband switching architecture

A simple architecture for broadband switching based on a multistage interconnection network without internal buffers is proposed. An acknowledgment-based mechanism to manage contention situations that arise in the routing network is provided. The proposed architecture can be used with different kinds of routing networks to obtain a compromise between performance and complexity. For this purpose, performance comparisons between some significant examples of routing networks are also presented.<>     

A photonic wavelength-division switching system using tunable laserdiode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. A switching system using wavelength switches and multistage switching networks is discussed. A crucial point in developing this switching system is to achieve a large number of wavelength-division channels. The potential of 100 wavelength-division channels in such switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization which permits the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift is proposed. An eight-channel wavelength-division switching experiment, using phase-shift-controlled distributed feedback laser diodes as tunable wavelength filters, is reported     

Crosstalk-free conjugate networks for optical multicast switching

High-speed photonic switching networks can switch optical signals at the rate of several terabits per second. However, they suffer from an intrinsic crosstalk problem when two optical signals cross at the same switch element. To avoid crosstalk, active connections must be node disjoint in the switching network. In this paper, a sequence of decomposition and merge operations, called conjugate transformation, performed on each switch element to tackle this problem, is proposed. The network resulting from this transformation is called the conjugate network. By using the numbering schemes of networks, the authors prove that if the route assignments in the original network are link disjoint, their corresponding ones in the conjugate network would be node disjoint. Thus, traditional nonblocking switching networks can be transformed into crosstalk-free optical switches in a routine manner. Furthermore, it has been shown that crosstalk-free multicast switches can also be obtained from existing nonblocking multicast switches via the same conjugate transformation.     

Approaches to optical Internet packet switching

Wavelength-division multiplexing is currently being deployed in telecommunications networks in order to satisfy the increased demand for capacity brought about by the explosion in Internet use. The most widely accepted network evolution prediction is via an extension of these initial predominantly point-to-point deployments, with limited system functionalities, into highly interconnected networks supporting circuit-switched paths. While current applications of WDM focus on relatively static usage of individual wavelength channels, optical switching technologies enable fast dynamic allocation of WDM channels. The challenge involves combining the advantages of these relatively coarse-grained WDM techniques with emerging optical switching capabilities to yield a high-throughput optical platform directly underpinning next-generation networks. One alternative longer-term strategy for network evolution employs optical packet switching, providing greater flexibility, functionality, and granularity. This article reviews progress on the definition of optical packet switching and routing networks capable of providing end-to-end optical paths and/or connectionless transport. To date the approaches proposed predominantly use fixed-duration optical packets with lower-bit-rate headers to facilitate processing at the network-node interfaces. Thus, the major advances toward the goal of developing an extensive optical packet-switched layer employing fixed-length packets are summarized, but initial concepts on the support of variable-length IP-like optical packets are also introduced. Particular strategies implementing the crucial optical buffering function at the switching nodes are described, motivated by the network functionalities required within the optical packet layer     

Optimizing complexity in Benes-type WDM switching networks

In this paper, we propose a new Benes-type wavelength division multiplexing (WDM) optical network with space-wavelength switching capability. Intuitively, adding wavelength switching capability to space Benes networks requires the use of additional hardware components (i.e., wavelength converters). However, in this paper, we show that a Benes network with full-permutation capability in both space and wavelength domains can be designed using a smaller number of hardware components but the same number of stages as that in a space-only Benes network. In addition, wavelength conversion in the proposed network occurs only between two pre-defined wavelengths, eliminating the need for any expensive wide-range wavelength converters. The proposed Benes network is based on the newly proposed concept of wavelength-exchangeable permutation networks. Wavelength-exchangeable networks implement single-step space and wavelength switching and hence reduces the number of hardware components. We show that, such wavelength-exchangeable networks possess some interesting properties that can be used for designing routing algorithms to improve signal quality.

A fault-tolerant switching network for B-ISDN

The author proposes a self-routing fault-tolerant switching network for asynchronous transfer mode (ATM) switching systems. The network has many subswitches to enhance the fault tolerance of the conventional multistage interconnection network which only has a unique path. The subswitches provide large numbers of alternative paths between switching stages and allow the network to tolerate multiple paths. The routing algorithm is quite simple. The paths can also be used to route cells under the condition that internal cell contentions occur in switching elements. A reliability analysis shows a quantitative measurement of the improvement in fault tolerance as compared with previously presented fault-tolerant networks. A performance analysis and simulation results show that the proposed network has a high level of maximum throughput. In addition, that level of throughput is maintained with reasonable cell delay even though the number of faulty components increases in the network     

Unified approaches to integrated-service networks–burst and fast packet switching

The increasing demand for communication services, coupled with recent technological advances in communication media and switching techniques, has resulted in a proliferation of new and expanded services. Currently, networks are needed which can transmit voice, data and video services in an application-independent fashion. Unified approaches employ a single switching technique across the entire network bandwidth, thus allowing services to be switched in an application-independent manner. This paper presents a taxonomy of integrated-service networks, including a look at NISDN, while focusing on unified approaches to integrated-service networks. The two most promising unified approaches are burst and fast packet switching. Burst switching is a circuit switching-based approach which allocates channel bandwidth to a connection only during the transmission of ‘bursts’ of information. Fast packet switching is a packet switching-based approach which can be characterized by very high transmission rates on network links and simple, hard-wired protocols which match the rapid channel speed of the network. Both approaches are being proposed as possible implementations for integrated-service networks. We survey these two approaches, and also examine the key performance issues found in fast packet switching. We then present the results of a simulation study of a fast packet switching network.     

Reconfigurable fault tolerant networks for fast packet switching

The authors consider the design and analysis of reconfigurable networks for fast packet switching. The design constraints resulting from the use of fast packet switching that affect fault-tolerant network design are carefully studied. A reconfigurable network with high link redundancy is then proposed. An abstract replacement model that characterizes the proposed reconfigurable network is presented. Network fault tolerance problems are transformed into well known assignment problems. Two practical designs based on feasible technology are presented. An appreciable reliability improvements is achieved and full bandwidth is maintained up to a tolerable level of failures, with relatively few spare switches     

Large modular expandable optical switching matrices

Large optical switching matrices can be assembled incrementally from identical modules by means of a rearrangement of the Clos architecture that we have labeled SKOL. The design retains the strict-sense nonblocking properties of the Clos design, identical units provide economies of manufacture, and there are also cost advantages associated with the incremental expandability. SKOL modules can be constructed in ways that do not map back to the Clos original. In this form, SKOL is a new multistage switching architecture that is well adapted for construction with integrated optical technologies. We anticipate that the SKOL design can provide the very large, expandable optical switching matrices now demanded for optical networks     

On nonblocking switching networks for multichannel connections

This paper deals with switching networks for multichannel connections. The conditions under which the three-stage switching network is nonblocking for s-channel connections are given. Switching networks that are nonblocking in the strict sense as well as the switching networks nonblocking in the wide sense are considered. The conditions for two-sided and for one-sided switching networks are derived     

Tree-type photonic switching networks

The enormous bandwidth offered by optical systems makes photonic switching a very attractive solution for broadband communications. Tree-type architectures play an important role in the design of photonic switching networks. The authors present and discuss all known tree-type space-division photonic switching networks architectures in a unified framework, and propose a number of new solutions. The discussed networks can be implemented with guided-wave-based switching elements, or laser diodes and passive splitters and combiners. The following network types are considered: conventional, simplified, and two-active stage networks. Techniques for improving SNR as well as waveguide crossover minimization are presented and discussed     

Neural networks for switching

The author argues that a strong impetus for using neural networks is that they provide a framework for designing massively parallel machines. He notes that the highly interconnected architecture of switching networks suggests similarities to neural networks. He presents two switching applications in which neural networks can solve the problems efficiently. He shows that a computational advantage can be gained by using nonuniform time delays in the network     

A block matrix representation of permutation networks

This work provides a mathematical framework for topologically-independent analysis of permutation networks. First, a structure-dependent representation is provided using matrices whose entries are switching expressions. Then, a transformation is presented which maps these matrices into structure-independent representations which are matrices whose entries are 0/1 matrices. Algebraic tools for manipulating the second type of matrices are also provided. Notions such as permutations realizable by a network, the rearrangeability property, and series and parallel connections of networks are defined and discussed with regard to the proposed representations.     

Hybrid switching and p-routing for optical burst switching networks

One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks.     

近红外量子通信网中单光子波长交换研究

提出了一种新的近红外多用户量子密钥分发中波长交换方案,解决了量子网络中信息交互难题;分析了交换过程中近红外单光子束的偏振变换;仿真了波长交换效率和泵浦光功率之间关系.仿真结果表明,该方案可行并且高效.