. With the increasing use of distributed hard real-time systems, the ability of computer networks to handle hard real-time message traffic is becoming more important. For traditional networks, maximizing the throughput or minimizing the average message delay is the most important performance criteria. In the hard real-time domain, however, concern focuses on satisfying the time constraints of individual messages. This paper examines recent developments in hard real-time communication in local area multiple-access networks. Two general strategies are used in hard real-time communication: the guarantee strategy and the best-effort strategy. In the former, messages are guaranteed to meet their deadlines during normal operation of the network. In the best-effort strategy, the network will attempt to send messages before their deadlines, but no guarantees are given. Real-time message traffic can be distinguished according to whether it is best suited for the guarantee strategy or the best-e...

We provide a comprehensive survey of packet-switched ring metro WDM networks.

All-optical networks that employ wavelength division multiplexing (WDM) are an attractive architecture for future high-speed networks. Through WDM, multiple channels are created on a single ber, and an aggregate network bandwidth far greater than the peak electronic processing speed can be realized. This paper provides a review and an extensive bibliography of proposed media access control (MAC) protocols for local area and metropolitan area single-hop broadcast-and-select WDM networks. 1 Introduction All-optical networks, where the entire path between end nodes is optical, represent the third generation in the use of ber in communication systems [1, 2]. In this generation, ber is used for its unique properties instead of merely as a replacement for copper. Wavelength division multiplexing (WDM) can be used to provide multiple channels on a single ber, each operating at a maximum data rate set by electronic technology [3, 4]. This technique avoids the electronic bottleneck d...

SONET/SDH ring networks, which are currently the dominant type of metropolitan area network, carry the increasingly bursty and and asymmetric traffic in the dynamically evolving metro area only inefficiently, resulting in the so-called “metro gap”. Therefore, metro WDM networks, which have typically either a star or ring topology, have recently received significant interest. In this paper we provide a comprehensive survey of ring metro WDM networks. We first review the current standardization and testbed activities and then provide a categorization for ring WDM networks. We categorize the networks according to the employed medium access control (MAC) protocols. Throughout we pay close attention to the key factors that govern the throughput-delay performance of the networks, such as the source vs destination stripping of the data packets from the ring and the a priori or a posteriori access strategies. We also consider the fairness aspects and the QoS support in the networks.