The rapid development of Asynchronous Transfer Mode technology in the last 10-15 years has stimulated renewed interest in the design and analysis of switching systems, leading to new ideas for system designs and new insights into the performance and evaluation of such systems. As ATM moves closer to realizing the vision of ubiquitous broadband ISDN services, the design of switching systems takes on growing importance. This paper seeks to clarify the key architectural issues for ATM switching system design and provides a survey of the current state-of-the-art.

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Architectural choices in large scale ATM switches

Two simple models of queueing on an N ?? N space-division packet switch are examined. The switch operates synchronously with fixed-length packets; during each time slot, packets may arrive on any inputs addressed to any outputs. Because packet arrivals to the switch are unscheduled, more than one packet may arrive for the same output during the same time slot, making queueing unavoidable. Mean queue lengths are always greater for queueing on inputs than for queueing on outputs, and the output queues saturate only as tbe utilization approaches unity. Input queues, on the other hand, saturate at a utilization that depends on N , but is approximately (2 - ?>2) = 0.586 when N is large. If output trunk utilization is the primary consideration, it is possible to slightly increase utilization of the output trunks??-??upto(1 - e -1 ) ?? 0.632 as N ?> ?>??-??by dropping interfering packets at the end of each time slot, rather than storing them in the input queues. This improvement is possible, however, only when the utilization of the input trunks exceeds a second critical threshold??-??approximately 1n (1 + ?>2) = 0.881 for large N .

Input Versus Output Queueing on a SpaceDivision Packet Switch

Computer networks are undergoing a remarkable transformation. The widespread use of optical fiber to transmit data has made tremendous increases in network bandwidth. Furthermore, greater CPU power, increasing disk capacity, and support for digital audio and video are creating demand for a new class of network services. For example, video-on-demand, distant learning, distant diagnosis, video conferences, and many others applications have popped up one after another in recent years. Many of these services have one thing in common. They all require that the same piece of data be sent to multiple recipients. Even in traditional networks, this operation, called multicasting, can not be handled easily and cheaply. When scaled up to high speed ATM-based networks, the situation could be worse. Multiple streams of data travel around ATM networks. Each tries to send to many different destinations simultaneously. Therefore, designing economical ATM network switches which can support multicasting operations easily is very important in the future generation high speed networks. In the past twelve years or so, many designs for multicasting ATM switches are proposed. It seems about time to do a historical survey. It is hoped that by learning from the wisdom of the previous authors, new spark or angle can be found and exploited to design new multicasting ATM switches. Without easy and inexpensive multicasting, all the exciting services may become unaffordable. This will in turn lead to the diminishing of customer bases and finally will hinder the full-scale deployment of high speed networks.

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Multicast ATM switches: survey and performance evaluation

Principles of Broadband Switching and Networking explains the design and analysis of switch architectures suitable for broadband integrated services networks, emphasizing packet-switched interconnection networks with distributed routing algorithms. The text examines the mathematical properties of these networks, rather than specific implementation technologies. Although the pedagogical explanations in this book are in the context of switches, many of the fundamental principles are relevant to other communication networks with regular topologies.

Principles of Broadband Switching and Networking

A signal monitoring apparatus and method involving devices for monitoring signals representing communications traffic, devices for identifying at least one predetermined parameter by analyzing the context of the at least one monitoring signal, a device for recording the occurrence of the identified parameter, a device for identifying the traffic stream associated with the identified parameter, a device for analyzing the recorded data relating to the occurrence, and a device, responsive to the analysis of the recorded data, for controlling the handling of communications traffic within the apparatus

Signal monitoring apparatus analyzing voice communication content

The paper describes several improvements to a nonblocking copy network proposed previously for multicast packet switching. The improvements provide a complete solution to some system problems inherent in multicasting. The input fairness problem caused by overflow is solved by a cyclic running adder network (CRAN), which can calculate running sums of copy requests starting from any input port. The starting point can change adaptively in every time slot based on the overflow condition of the previous time slot. The CRAN also serves as a multicast traffic controller to regulate the overall copy requests. The throughput of a multicast switch can be improved substantially if partial service of copy request is implemented when overflow occurs. Call-splitting can also be implemented by the CRAN in a straightforward manner. Nonuniform distribution of replicated packets at outputs of the copy network may affect the performance of the following routing network. This output fairness problem due to underflow is solved by cyclically shifting the copy packets in every time slot. An approximate queueing model is developed to analyze the performance of this improved copy network. It shows that if the loading on each output of the copy network is maintained below 80%, the average packet delay in an input buffer would be less than two time slots. >

Jae W. Byun

Papers

The design and analysis of an ATM multicast switch with adaptive traffic controller