Multicast Connections Research Articles

Multicast Space-Conversion-Space Strict-Sense Nonblocking Switching Fabrics with Multicast Opportunity in the Last Stage for Continuous Multislot Connections

This paper introduces two nonblocking switching fabric architectures designed for multicast connections. These connections are defined using the multislot connection approach, mainly applied in elastic optical networks. In contrast to earlier solutions, this approach assumes that multislot connections are consistently established in adjacent continuous slots. This implies that previously established solutions could not be applied. Our study presents a comprehensive theoretical framework applicable to the general case of three-stage switching fabrics. These fabrics feature external stages equipped with space switches, while the middle stage incorporates conversion switches that operate in the wavelength, time, or frequency domain. In addition, multicast capabilities are deliberately confined to the output-stage switch or switches. A fundamental contribution of this work lies in the formulation of the worst-case scenario, which serves as the foundational basis for deriving strict-sense nonblocking conditions governing such multicast switching fabrics. Our analysis formally demonstrates that the fundamental structure of the multicast nonblocking switching fabric aligns closely with that of the previously examined point-to-point fabric. The only difference is related to the ability to multicast within the output stage of the switching fabric.

Rearrangeability and repackability of a multicast wavelength-space-wavelength elastic optical network

Elastic optical networks (EONs) have been introduced to meet the demands of the rapidly growing Internet. These networks can efficiently keep up with the emerging bandwidth-hungry and highly dynamic services, and can support multicast services using techniques like the path, tree or subtree methods. A multicast wavelength-space-wavelength (M-WSW) network is a switching node architecture for EONs, which adopts the subtree method to support multicast connections. An M-WSW network consists of three node stages in which wavelength, space and wavelength switches are used, respectively. A nonblocking M-WSW network guarantees that any connection between a free input and a free output can always be realized, and studying the nonblockingness of a network has attracted much attention from researchers. Sufficient conditions, in terms of the number of middle space switches, for an M-WSW network to be strict-sense nonblocking (SNB) or wide-sense nonblocking (WSNB) were examined in an earlier study. It is known that SNB networks usually incur a higher hardware cost, for instance, the number of middle space switches, compared to WSNB, rearrangeably nonblocking (RNB), or repackably nonblocking (RPNB) networks. This paper studies the rearrangeability and repackability of M-WSW networks, and derives the sufficient and necessary conditions for an M-WSW network to be RNB (or RPNB). The results show that the derived sufficient conditions for being RNB (or RPNB) require significantly fewer middle switches for SNB and WSNB networks, and the RPNB results require fewer middle switches than those for RNB in most cases.

DYNAMIC MULTICAST SPECTRUM (RE) ALLOCATION USING SHARED BACKUP PATH IN ELASTIC OPTICAL NETWORKS

The routing and spectrum allocation (RSA) problem in elastic optical networks (EON) is to first find a path for a connection request and then allocate a frequency slot to it. Due to spectrum continuity and contiguity constraints, some available frequency slots cannot be allocated to connection requests. In this case, one solution is to reassign slot to some existing connections to accept new ones. However, most current reallocation schemes are proposed for unprotected connections. With the very high throughput of connections in EONs (Tb/s per link), the requirement for connection protection is becoming standard. In this paper, we examine a frequency slot reallocation approach for protected multicast connections. The proposed approach allows the reallocation of available and already used slots by temporarily using the protection resources. The experimental results show an average blocking probability of 10% lower than reallocation with hoptuning and the conventional MC-RSA algorithm.

Modeling of Multi-Service Switching Networks With Multicast Connections

This article presents an analytical model of a switching network that can be used in the nodes of a large number of modern multi-service networks. The model of a multi-service three-stage switching network proposed in this article has the advantage of providing the possibility to evaluate the point-to-point blocking probability for multicast connections. The information obtained in this way can then be used both at the stage of the estimation of the capacity of a new network and during the optimisation process of an existing network. In the calculations performed during the investigations, three scenarios for the fan out of multicast connections in the switching network are taken into consideration. The assumption is that the branching of a connection can occur in the first, second and the third stage of the switching network. The model proposed in the article is based on the concept of “effective” availability. The article discusses the methods for the determination of the effective availability parameter for successive connections that belong to a given multicast connection. The results of the analytical modelling are compared with the simulation data for three selected structures of multi-service switching networks to which different mixtures of multi-service BPP traffic are offered. The results of the calculations and the data provided by the simulation experiments validate and confirm high accuracy of the proposed model. This allows the model to be easily applied in practice to different environments to evaluate the capacities of the nodes in multi-service networks.

Fault-tolerant multicast routing in infocommunication network with path and bandwidth protection

The article presents and investigates a flow-based mathematical model of fault-tolerant multicast routing. Under the proposed mathematical model, the technical task of fault-tolerant multicast routing was reduced to the Boolean programming optimization problem. The mathematical model was based on linear optimality criterion and constraints represented by the conditions of single-path routing, flow conservation, multicast connectivity, and prevention of overload and looping. The routing variables that guided the multicast routing process were Boolean. The optimal primary and backup paths are calculated by implementing path and bandwidth protection schemes within the model for each multicast flow. The restrictions on routing variables introduced into the model were responsible for protecting the route and bandwidth. The optimality criterion in determining the optimal and backup multicast paths at the level of routing metrics considered the network topology and links bandwidth. The additive nature of the criterion focused on finding paths that included a minimum number of communication links. According to the selected routing metric, a feature of the model is to ensure priority in assigning the primary route of the path that had a shorter «length» than the backup path. The analysis of the obtained solutions confirmed their operability under the specified protection scheme’s implementation and their optimality according to variants of the used routing metrics. The proposed mathematical model can be used to develop the fault-tolerant multicast routing protocols of multimedia flows.

Sub-Tree-Based Approach for Reconfiguration of Light-Tree Pair without Flow Interruption in Sparse Wavelength Converter Network

Network reconfiguration is an important mechanism for network operators to optimize network performance and optical flow transfer. It concerns unicast and multicast connections. Multicast connections are required to meet the bandwidth requirements of multicast applications, such as Internet Protocol-based TeleVision (IPTV), distance learning, and telemedicine. In optical networks, a multicast connection is made possible by the creation of an optical tree-shaped path called a light-tree. The problem of light-tree pair reconfiguration is addressed in this study. Given an initial light-tree used to transfer an optical flow and a final light-tree that is computed by the network operator to optimize network performance, the goal is to migrate the optical flow from the initial light-tree to the final light-tree without flow interruption. Flow interruption is not desirable for network operators because it forces them to pay financial penalties to their customers. To solve this problem, existing methods use a branch approach that is inefficient if some network nodes do not have wavelength conversion capability. Therefore, we proposed in this study a sub-tree-based method. This approach selects and configures sub-tree pairs from the light-tree pair (initial light-tree, final light-tree) to be reconfigured. Then, we produce a sequence of configurations. The performance study confirms that our method is efficient in solving the problem of light-tree pair reconfiguration because our method does not cause flow interruption.

Dynamic multicast traffic grooming in light-trail WDM optical mesh networks

A light trail in a WDM optical network is an optical communication channel that allows intermediate nodes to access the channel providing the flexibility for multiplexing traffic of multiple connections into the optical communication channel at intermediate nodes. The technique of multiplexing traffic of multiple connections into a single communication channel is known as traffic grooming. This paper studies the problem of dynamic multicast traffic grooming that deals with dynamically arriving and departing multicast connections in light-trail WDM optical networks. Our objective is to reduce blocking ratio. This paper proposes an auxiliary graph model for light-trail WDM optical networks that can be used for routing and traffic grooming purposes. Based on the auxiliary graph model, two dynamic multicast traffic grooming algorithms are studied. Compared with existing algorithms in the literature, the two algorithms yield significantly better performance.

Quantitative Analysis of Multistage Switching Networks for Embedded Programmable Devices

This paper analyzes the properties of a class of congestion-free multistage switching networks (MSSNs) are butterfly-based and suitable for embedded programmable devices, which require sustaining static multicast connectivity. These MSSNs are fully synthesizable and enable the design of programmable IPs with typical size in the order of 1 KLUT, coupling flexibility with fast turn-around time. The non-blocking property for static connection of this class of MSSN is discussed. Our analysis shows pros and cons of adopting radix-2 or radix-4 MSSN structures, as well as the impact of bypass-paths to make the network fully hierarchical and locality-aware thanks also to a dedicated programming strategy. Implementation experiments carried out on STM CMOS 65 nm technology show the availability of various area-speed trade-offs, resulting in a range of ≃2× in frequency and a range of ≃ 4 × in area. Depending on the specific application-field, an optimal interconnect definition is thus achieved without compromising the routability properties. In this respect, the paper proposes a simplified application-driven model for evaluation of the best MSSN, including bypass-adoption and radix selection.

A Novel Multicast Scheme with Grooming for Quality of Service (QoS) Provision and Resource Optimization over Optical Label Switching (OLS) Networks

Abstract Optical label switching is proposed for providing fast all-optical switching, covering all granularities transfer and assuring quality of service support. However, the important issue is improving optical resource and providing a steadiness between satisfying traffic demands and reducing resource utilization. This paper proposes a novel multicast approach which enables grooming using an upgraded core node architecture that switches suitably unicast and multicast connections. The proposed node architecture manages appropriately all optical resource including a fiber delay line and wavelength bandwidth, as well as traffic requirements. A new label framework is introduced to assure the required information exchange for handling suitably real-time traffic constraints and optical resource status. Moreover, innovative signaling and switching schemes are introduced to perform suitably lightpath and traffic constraints supervision. Theoretical model and simulation experiments are conducted for validating the proposed scheme and evaluating its performances and effectiveness. Finally, the proposal guarantees traffic requirements and reduces resource usage while improving resource availability.

Reliability evaluation of a multicast over coded packet networks

Network coding is a generalization of conventional routing methods that allows a network node to code information flows before forwarding them. While it has been theoretically proved that network coding can achieve maximum network throughput, theoretical results usually do not consider the stochastic nature in information processing and transmission, especially when the capacity of each arc becomes stochastic due to failure, attacks, or maintenance. Hence, the reliability measurement of network coding becomes an important issue to evaluate the performance of the network under various system settings. In this paper, we present analytical expressions to measure the reliability of multicast communications in coded networks, where network coding is most promising. We define the probability that a multicast rate can be transmitted through a coded packet network under a total transmission cost constraint as the reliability metric. To do this, we first introduce an exact mathematical formulation to construct multicast connections over coded packet networks under a limited transmission cost. We then propose an algorithm based on minimal paths to calculate the reliability measurement of multicast connections and analyze the complexity of the algorithm. Our results show that the reliability of multicast routing with network coding improved significantly compared to the case of multicast routing without network coding.

A Linear Network Code Construction for General Integer Connections Based on the Constraint Satisfaction Problem

The problem of finding network codes for general connections is inherently difficult in capacity constrained networks. Resource minimization for general connections with network coding is further complicated. Existing methods for identifying solutions mainly rely on highly restricted classes of network codes, and are almost all centralized. In this paper, we introduce linear network mixing coefficients for code constructions of general connections that generalize random linear network coding for multicast connections. For such code constructions, we pose the problem of cost minimization for the subgraph involved in the coding solution and relate this minimization to a path-based constraint satisfaction problem (CSP) and an edge-based CSP. While CSPs are NP-complete in general, we present a path-based probabilistic distributed algorithm and an edge-based probabilistic distributed algorithm with almost sure convergence in finite time by applying communication free learning. Our approach allows fairly general coding across flows, guarantees no greater cost than routing, and shows a possible distributed implementation. Numerical results illustrate the performance improvement of our approach over existing methods.

Rearrangeability of Multicast Banyan-Type Networks with Crosstalk Constraints

Multicast interconnection networks are highly demanded in parallel computing and communication networks. In the paper, we give the necessary and sufficient conditions the rearrangeability of the numbers of planes needed for 2j-cast Banyan-type networks with crosstalk constraints and j being a nonnegative integer. Our results of the paper are extended for multicast connection requests, while the previous study results in the paper of Chen et al. are just for a special case for j = 0 and one-to-one connection requests.

A Self-Routing on-Chip Network

This paper introduces a new nonblocking self-routing network, called a multi-root binary tree, which may be used to interconnect the cores in multicore chips. The multi-root binary tree network differs from other binary tree-based networks in that the cores are placed at the roots rather than the leaves or the interior nodes of the trees. The self-routing property of a multi-root binary tree is built on the concept of replication and clustering. A new replication and clustering method, called the triangular shift pairing is given to connect the cores together over dedicated paths. It is shown that connecting cores in clusters requires at least n=2 columns of pairings for an n-core network in a grid layout model and triangular shift wiring method matches this lower bound. The replication and clustering concept leads to a simple self-routing scheme that pairs cores by decoding both unicast and multicast connection requests using lg n-bit cluster address bits. In particular, it is established that cores can identify the cluster with which they pair with other cores using simple modulo addition of their own ids and addresses of the targeted cores in 2lg n single bit-decoding steps. It is also shown that, if connection requests are uniformly distributed among the cores then blocking due to target conflicts can be avoided if cores serve connection requests at a small multiple of the frequencies with which they receive them.

Design and matrix analysis of optical switch with multicast function using general MZI

Based on the analysis of the LiNbO3 Mach-Zehnder interferometer (MZI), a MZI with three optical switch functions (direct connection, cross connection and multicast connection) is demonstrated in this paper. With this MZI, a 4×4 optical switch is then proposed. The optical switch not only switches optical signal from one channel to another (1:1), but also from one channel to several channels (1: k) with non-blocking and duplex communication. Later, a matrix analysis on the optical switch proposed is given. In the end of this paper, an example of the transmission path and the controlling state of the optical switch is demonstrated.

Performance Analysis of a Data-Driven Quality-of-Transmission Decision Approach on a Dynamic Multicast-Capable Metro Optical Network

The performance of a data-driven quality-of-transmission (QoT) model is investigated on a dynamic metro optical network capable of supporting both unicast and multicast connections. The data-driven QoT technique analyzes data of previous connection requests and, through a training procedure that is performed on a neural network, returns a data-driven QoT model that near-accurately decides the QoT of the newly arriving requests. The advantages of the data-driven QoT approach over the existing Q-factor techniques are that it is self-adaptive, it is a function of data that are independent from the physical layer impairments (PLIs) eliminating the requirement of specific measurement equipment, and it does not assume the existence of a system with extensive processing and storage capabilities. Further, it is fast in processing new data and fast in finding a near-accurate QoT model provided that such a model exists. On the contrary, existing Q-factor models lack self-adaptiveness; they are a function of the PLIs, and their evaluation requires time-consuming simulations, lab experiments, specific measurement equipment, and considerable human effort. It is shown that the data-driven QoT model exhibits a high accuracy (close to 92%–95%) in determining, during the provisioning phase, whether a connection to be established has a sufficient (or insufficient) QoT, when compared with the QoT decisions performed by the Q-factor model. It is also shown that, when sufficient wavelength capacity is available in the network, the network performance is not significantly affected when the data-driven QoT model is used for the dynamic system instead of the Q-factor model, which is an indicator that the proposed approach can efficiently replace the existing Q-factor model.

On control plane algorithms for Carrier Ethernet networks: Unicast, multicast provisioning and control traffic reduction

Carrier Ethernet systems are actively replacing SONET/SDH networks for transport of provider data. After much standardization in both the IEEE and the IETF, Carrier Ethernet has evolved as a rich carrier-class technology. The standards do not focus on specific implementation aspects of providing guaranteed service-oriented features that are intrinsic towards successful replacement of SONET/SDH by Carrier Ethernet solutions. In this paper, we consider the engineering aspects of the Carrier Ethernet software defined control plane for provisioning, managing and maintaining services. Specifically, we propose methods for provisioning guaranteed unicast services considering the underlying network state. The problem is difficult due to the complex nature of admission control coalesced with subjective user requirement that is not easy to rationalize across a network. We also investigate the problem of sub-50ms protection of multicast connections and propose a unique, tractable algorithm within the control plane for enabling carrier-class multicast services. Finally, we focus on overall control traffic reduction schemes. An intuitive merging algorithm is proposed that minimizes control traffic in Carrier Ethernet domains. A simulations study extensively evaluates the proposed techniques.

Designing, Operating, and Reoptimizing Elastic Optical Networks

Emerging services and applications demanding high bitrate and stringent quality of service requirements are pushing telecom operators to upgrade their core networks based on wavelength-division multiplexing (WDM) to a more flexible technology for the more dynamic and variable traffic that is expected to be conveyed. Finally, academy- and industry-driven research on elastic optical networks (EON) has turned out into a mature enough technology ready to gradually upgrade WDM-based networks. Among others, key EON features include flexible spectrum allocation, connections beyond 100 Gb/s, advanced modulation formats, and elasticity against time-varying traffic. As a consequence of the variety of features involved, network design and algorithms for EONs are remarkably more complex than those for WDM networks. However, new opportunities for network operators to reduce costs arise by exploiting those features; in fact, the classical network life cycle based on fixed periodical planning cycles needs to be adapted to greatly reduce overprovisioning by applying reoptimization techniques to reconfigure the network while it is in operation and to efficiently manage new services, such as datacenter interconnection that will require provisioning multicast connections and elastic spectrum allocation for time-varying traffic. This paper reviews and extends mathematical models and algorithms to solve optimization problems related to the design, operation, and reoptimization of EONs. In addition, two use cases are presented as illustrative examples on how the network life cycle needs to be extended with in-operation planning and data analytics thus adding cognition to the network.

A robust optimization approach for multicast network coding under uncertain link costs

Network coding is a technique that can be used to improve the performance of communication networks by performing mathematical operations at intermediate nodes. An important problem in coding theory is that of finding an optimal coding subgraph for delivering network data from a source node throughout intermediate nodes to a set of destination nodes with the minimum transmission cost. However, in many real applications, it can be difficult to determine exact values or specific probability distributions of link costs. Establishing minimum-cost multicast connections based on erroneous link costs might exhibit poor performance when implemented. This paper considers the problem of minimum-cost multicast using network coding under uncertain link costs. We propose a robust optimization approach to obtain solutions that protect the system against the worst-case value of the uncertainty in a prespecified set. The simulation results show that a robust solution provides significant improvement in worst-case performance while incurring a small loss in optimality for specific instances of the uncertainty.

Multicast Connections in Wireless Sensor Networks with Topology Control

The article explores the quality of multicast trees constructed by heuristic routing algorithms in wireless sensor networks where topology control protocols operate. Network topology planning and performance analysis are crucial challenges for wire and wireless network designers. They are also involved in the research on routing algorithms, and protocols for these networks. In addition, it is worth to emphasize that the generation of realistic network topologies makes it possible to construct and study routing algorithms, protocols and traffic characteristics for WSN networks.

Tabu Search for Low-Cost Dynamic Multicast Tree Generation with Quality of Service Guarantees

AbstractIn a communication network with a source node, a multicast tree is defined as a tree rooted at the source node and all its leaves being recipients of the multicast originating at the source. The tree or bandwidth cost is normally measured by its utilization of tree links along with the quality of service (QoS) measures such as delay constraint and end-to-end delay. However, if nodes are allowed to join or leave the multicast group at any time during the lifetime of the multicast connection, then the problem is known as dynamic multicast routing problem. In this article, we combine a greedy approach with static multicast routing using Tabu Search to find a low-cost dynamic multicast tree with desirable QoS parameters. The proposed algorithm is then compared with several static multicast routing algorithms. The simulation results show that, on a large number of events, i.e., where nodes are leaving or joining, the proposed algorithm is able to find multicast trees of lower cost and more desirable QoS properties.