In the original shared buffer memory switch, there exists inherent unfairness since multicast cells always own higher priority to be served such that unicast cells must endure longer delay time. We propose a multicasting balancing method to overcome this unfair phenomenon in which the service order for two kinds of cells is decided by a ratio of unicast queue length and multicast queue length for each output port. Performance results are provided to verify the effectiveness.

This paper studies routing methods for the complete broadcast multipoint-to-multipoint communication. For a Z-node (Z-site) of the participants of the connection, each site transmits one signal and receives Z-1 signals. The routing method based on connecting each participant by multiple directed point-to-point circuits uses wasteful bandwidth that the source-to-destination data may be duplicated needlessly. We propose routing methods that the connection approach is based on setting multicast tree routes that each participant (site) has one own multicast tree connecting to the other participants under two constraints: the delay-bounded constraint of source-destination path and the available constrained bandwidth for the service of links. For this routing approach, we propose both heuristic algorithm finding approximate solution and search enumeration based algorithm finding optimal solution, and compare the approximate solution with the optimal solution. This approach can lower costs for the subscribers and conserves bandwidth resources for the network providers.

By addressing design requirements for multicast ATM switching, this paper attempts to provide an integrated view of modular and expandable switch architectures suitable for both unicast and multicast switching for future B-ISDNs. Several large and modular multicast ATM switching architectures are discussed, each of which handles different traffic situations. These architectures consist of multiple shared-buffer copy network modules of adequate size suitable for fabrication on a single chip, and small output memory switch modules. A new modular link-grouped multistage interconnection network is proposed for interconnecting copy network modules and memory switch modules, so that future large multicast ATM switching networks can be built in a modular fashion. The described modular architectures can significantly facilitate signal synchronization in large-scale switching networks.

With the arrival of B-ISDN, widespread usage of multicast services such as TV broadcasting and video 900 services will increase the possibility of network congestion unless efficient multiple destination routing (MDR) algorithms are used. Current MDR algorithms using link cost based on bandwidth usage or distance to compute the minimum cost routing tree do not take into account the vast amount of information collected by intelligent network (IN) databases. In this paper, we propose a multicast routing algorithm which modifies the way the cost is calculated by using the predicted traffic statistics collected by IN databases. We also show that the traffic handling characteristics vastly improved over conventional MDR algorithms.

As promising copy networks of very large multicast switching networks for Broadband ISDN, multi-stage Recursive Copy Networks (RCN) have been proposed recently. In the multicast switch structure, the RCN precedes a point-to-point switch. At an RCN, all the copies of a master cell are generated recursively, i.e., a few copies of the master cell are made initially, and by considering each of these copies to be master cells, more copies are made which, in turn, are again considered to be master cells to make still more copies, the process thus progressing recursively till all the required copies are made. By this principle of recursive generation of copies, the number of copies that can be generated is independent of the hardware size of the RCN. A limitation of RCNs is that buffer sizes at all stages except the first stage have to be large so as to keep the cell loss due to buffer overflow within desired limits. This paper inspects a flow control scheme by which the probability of buffer overflow can be kept low, even though the buffer sizes at later stages are not large. Under this flow control procedure, a cell is not transmitted from a stage to the succeeding stage, if the occupancy level of the buffer of the succeeding stage exceeds a threshold. We study by simulation the performance aspects of such a flow control scheme in RCNs under cut-through switching scheme and under store-and-forward switching scheme. At high load intensities, the overflow probability can be reduced by an order of magnitude in 2-stage RCNs and by two orders of magnitude in 3-stage RCNs. To restrict the overflow probability within a given limit, the required buffer size is less under flow control than under no flow control. The implementation of the flow control is simple and the control overhead is small, thereby making the scheme attractive for implementation in high speed switching environments. Further, the proposed flow control scheme does not disturb the cell sequence.

With the arrival of B-ISDN, point-to-point routing alone is no longer adequate. A new class of computer and video related services, such as mass mailing, TV broadcasting, teleconferencing, and video 900 service, requires the network to handle multiple destination routing (MDR). Multiple destination routing enables widespread usage of multipoint services at a lower cost than networks using point-to-point routing. With this in mind, network providers are researching more into MDR algorithms. However, the MDR problem itself is very complex. Furthermore, its optimal solution, the Steiner tree problem, is NP-complete and thus not suitable for real-time applications. Recently, various algorithms which approximate the Steiner tree problem have been proposed and, in this invited paper, we will summarize the simulation results of these algorithms. But first, we will define the MDR problem, the issues involved, and the benchmark used to compare MDR algorithms. Then, we will categorize the existing MDR algorithms into a five-level classification tree. Lastly, we will present various published results of static algorithms and our own simulation results of quasi-static algorithms.

A high-speed data communication service such as inter-LAN is one of many services possible with ATM-based B-ISDN. Design objectives were to simplify the connection setup procedure, to ensure efficient utilization of network capacity, and to reduce delay in servers. These objectives were met in a B-ISDN service trial system featuring distributed connectionless servers connected by permanent virtual channels and cell-by-cell processing in the connectionless server. The system's eight connectionless servers accommodate up to 256 subscriber network interfaces. The authors discuss how multicast can be provided in ATM-based connectionless data networks for inter-LAN communications. Four possible configurations, distinguished by copy function (multicast/broadcast) and on functional arrangement in the inter-connectionless server network (centralized/distributed), are presented. The configurations are compared from perspectives of required hardware and network capacity. The distributed broadcast function is shown the most reasonable solution.

Two types of multicast error control protocols based on a product code structure with or without interleaving are considered. The performances of these protocols are analyzed on burst error channels modeled by Gilbert's two-state Markov chain. The numerical results reveal that the interleaving does not always succeed in improving the performance of the protocol proposed in Part .

A multicast error control protocol proposed by Metzner is generalized and the performance of the proposed protocol on random error channels (binary symmetric channels) is analyzed. The proposed protocol adopts an encoding procedure based on a product code structure, whith enables each destined user terminal to decode the received frames with the Reddy-Robinson algorithm. As a result, the performance degradation due to the re-broadcasting of the replicas of the previously transmitted frames can be circumvented. The numerical results for the analysis and the simulation indicate that the proposed protocol yields higher throughput and less degradation of throughput with an increase of the number of destined terminals.

This paper presents a new architecture of a copy network which employs the principle of recursive generation of copy cells. The proposed architecture achieves high utilization of the links and buffers of the copy network, and preserves the cell sequence. The architecture lends itself modularity so that large multicast ATM switches can be fabricated by employing the proposed copy network. Two different modular structures - one for reduced latency of the unicast cell and the master cell from which copies are made, and the other for reduced hardware overhead - for realizing large multicast ATM switches are configured. The hardware of functional elements of the copy network are the same as those of the functional elements of a modular point-to-point switch proposed earlier, thereby resulting in the modularity of functional elements as well. Simulation studies show that the proposed copy network achieves high throughput and low cell loss probability, and the required buffer sizes are small. The delay of cells is found to be very small for traffic loads up to 90%.