Real-time and scalable multicast services are of paramount importance to Industrial Internet of Things (IIoT) applications. To realize these services, the multicast algorithm should, on the one hand, ensure the maximum delay of a multicast session not exceeding its upper delay bound. On the other hand, the algorithm should minimize session costs. As an emerging networking paradigm, Software-defined Networking (SDN) can provide a global view of the network to multicast algorithms, thereby bringing new opportunities for realizing the desired multicast services in IIoT environments. Unfortunately, existing SDN-based multicast (SDM) algorithms cannot meet the real-time and scalable requirements simultaneously. Therefore, in this paper, we focus on SDM algorithm design for IIoT environments. To be specific, the paper first converts the multicast tree construction problem for SDM in IIoT environments into a delay-bounded least-cost shared tree problem and proves that it is an NP-complete problem. Then, the paper puts forward a shared tree (ST) algorithm called SDM4IIoT to compute suboptimal solutions to the problem. The algorithm consists of five steps: 1) construct a delay-optimal shared tree; 2) divide the tree into a set of subpaths and a subtree; 3) optimize the cost of each subpath by relaxing the delay constraint; 4) optimize the subtree cost in the same manner; 5) recombine them into a shared tree. Simulation results show that the algorithm can provide real-time support that other ST algorithms cannot. In addition, it can achieve good scalability. Its cost is only 20.56% higher than the cost-optimal ST algorithm. Furthermore, its computation time is also acceptable. The algorithm can help to realize real-time and scalable multicast services for IIoT applications.

Interactive multimedia applications (IMAs) require not only adequate bandwidth to support large volume data transmission but also bounded end-to-end transmission delay between end users. This study proposes a Delay and Degree constrained Multicasting Spanning Tree (D2MST) algorithm to build an any-to-any share tree for IMAs. D2MST comprises root selection and spanning tree generation. A weighting function is defined based on the novel concept of network center and gravity to choose the root of a share tree. From the root, a spanning tree is built by incrementally connecting nodes with larger "power" to the tree so that the degree constraint is satisfied. Simulation results show that D2MST can successfully generate a Δ-constraint MST in which a high percentage of nodes can interact within the bounded delay.

Cluster computation has been used in the applications that demand performance, reliability, and availability, such as cluster server groups, large-scale scientific computations, distributed databases, distributed media-on-demand servers and search engines etc. In those applications, multicast can play the vital roles for the information dissemination among groups of servers and users. This paper proposes a set of novel efficient fault-tolerant multicast routing algorithms on hypercube interconnection of cluster computers using multicast shared tree approach. We present some new algorithms for selecting an optimal core (root) and constructing the shared tree so as to minimize the average delay for multicast messages. Simulation results indicate that our algorithms are efficient in the senses of short end-to-end average delay, load balance and less resource utilizations over hypercube cluster interconnection networks.

In this paper, a new multicast routing method for layered streams is proposed. This method is an extension of the weighted greedy algorithm (WGA) and uses two kinds of weight values to refine the link distance. It can cope with dynamic change in the group members without multicast tree re-construction. The method is compatible with the RSVP and can be utilized in existing shared tree type routing protocols such as CBT and PIM sparse mode. The network resources can be utilized efficiently; furthermore, the loss rate of member's requests to receive more layers can be reduced by this routing method when a sufficient number of nodes have the packet filtering function and a sufficient number of hops is permitted.

The main issues of the next generation Internet are high performance multicast, security and QoS (Quality of Service). The network layer multicast is accepted as a powerful solution to reduce communication overhead in networks as well as hosts. Although a lot of multicast routing protocols have been developed and have worked for the current Internet, they have drawbacks in scalability, reliability and network load balancing. In this paper, we propose an enhanced multicast routing protocol called DCBT (Decentralized Core based Tree), which includes some features of CBT (Core Based Tree), PIM-SM (Protocol Independent Multicast-Sparse Mode) and BGMP (Border Gateway Multicast Protocol). Fundamentally DCBT differs from those in that it covers not only intra-region but also inter-region multicast. RNs (Regional networks) have their intra-region shared trees, which are interconnected by an inter-region shared tree for a multicast group. New two concepts are introduced: the one is RBTS (Region Based Tree Switching) to achieve network load balancing and the other is to redefine TOS (Type Of Service) byte to make special multicast routing decision. In addition, the effect of core location is given by changing its position within an RN. Finally we provide the performance evaluation of DCBT by OPNET network simulator over a real scale network model.