A proposal of a minimal-state processing search algorithm for isochronous channel reuse problems in DQDB networks

The IEEE 802.6 MAC standard protocol defines the distributed-queue dual bus (DQDB) for metropolitan area networks (MANs). The isochronous channel reuse problem (ICRP) has been studied for the efficient use of DQDB. Given a set of established connections and a set of connection requests, the goal of ICRP is to maximize the number of satisfied requests by finding a proper channel assignment, such that no established connection is not only reassigned a channel, but also any pair of active connections does not interfere each other. We propose a minimal-state processing search algorithm for ICRP (MIPS/sub -/ICRP). The simulation results show that MIPS/sub -/ICRP always provides near-optimum solutions

Optical-drop wavelength assignment problem for wavelength reuse in WDM ring metropolitan area networks

This paper presents a formulation of the optical-drop wavelength assignment problem (ODWAP) and its heuristic algorithm for WDM ring networks. The wavelength-division multiplexing (WDM) technology has been popular in communication societies for providing very large communication bands by multiple lightpaths with different wavelengths on a single optical fiber. Particularly, a double-ring optical network architecture based on the packet-over-WDM technology such as the HORNET architecture has been studied as a next generation platform for metropolitan area networks (MANs). Each node in this architecture is equipped with a wavelength-fixed optical-drop and a tunable transmitter so that a lightpath can be established between any pair of nodes without wavelength conversions. In this paper, we formulate ODWAP for efficient wavelength reuse under heterogeneous traffic in this network. Then, we propose a simple heuristic algorithm for ODWAP. Through extensive simulations, we demonstrate the effectiveness of our approach in reducing waiting times for packet transmissions when a small number of wavelengths are available to retain the network cost for MANs

High speed protocols for dual bus and dual ring network architectures

In this dissertation, two channel access mechanisms providing fair and bandwidth efficient transmission on dual bus and dual ring networks with high bandwidth-latency product are proposed. In addition, two effective priority mechanisms are introduced to meet the throughput and delay requirements of the diverse arrays of applications that future high speed networks must support. For dual bus architectures, the Buffer Insertion Bandwidth Balancing (BI_BWB) mechanism and the Preemptive priority Bandwidth Balancing (P_BI_BWB) mechanism are proposed. BI_BWB can significantly improve the delay performance of remote stations. It achieves that by providing each station with a shift register into which the station can temporarily store the upstream stations\u27 transmitted packets and replace these packets with its own transmissions. P_BI_BWB, an enhancement of BI_BWB, is designed to introduce effective preemptive priorities. This mechanism eliminates the effect of low priority on high priority by buffering the low priority traffic into a shift register until the transmission of the high priority traffic is complete. For dual ring architectures, the Fair Bandwidth Allocation Mechanism (FBAM) and the Effective Priority Bandwidth Balancing (EP_BWB) mechanism are introduced. FBAM allows stations to reserve channel bandwidth on a continuous basis rather than wait until bandwidth starvation is observed. Consequently, FBAM does not have to deal with the difficult issue of identifying starvation, a serious drawback of other access mechanisms such as the Local and Global Fairness Algorithms (LFA and GFA, respectively). In addition, its operation requires a significantly smaller number of control bits in the access control field of the slot and its performance is less sensitive to system parameters. Moreover, FBAM demonstrates Max-Min flow control properties with respect to the allocation of bandwidth among competing traffic streams, which is a significant advantage of FBAM over all the previously proposed channel access mechanisms. EP_BWB, an enhancement of FBAM to support preemptive priorities, minimizes the effect of low priority on high priority and supports delay-sensitive traffic by enabling higher priority classes to preempt the transmissions of lower priority classes. Finally, the great potential of EP_BWB to support the interconnection of base stations on a distributed control wireless PCN carrying voice and data traffic is demonstrated

Extremely high data-rate, reliable network systems research

Significant progress was made over the year in the four focus areas of this research group: gigabit protocols, extensions of metropolitan protocols, parallel protocols, and distributed simulations. Two activities, a network management tool and the Carrier Sensed Multiple Access Collision Detection (CSMA/CD) protocol, have developed to the point that a patent is being applied for in the next year; a tool set for distributed simulation using the language SIMSCRIPT also has commercial potential and is to be further refined. The year's results for each of these areas are summarized and next year's activities are described

Fair and efficient transmission over GBPS dual ring networks

The advances in fiber optics technology provide large bandwidth and enable the support of a wide variety of services. New network architectures have been proposed, such as Metaring and Distributed Queue Dual Bus (DQDB), that try to take advantage of the new capabilities. Because of the very small packet transmission time relative to the feedback time a challenging issue in high speed networks is the efficient and fair share of the channel bandwidth among the competing users. In this thesis we first investigate and compare the performance of the Global and Local Fairness Mechanisms (GFM and LFM, respectively). They have been proposed recently for fair bandwidth allocation in high speed dual ring networks employing destination release. (a slot that has been read by its destination is immediately released and can be used again by other nodes). We show the sensitivity of both mechanisms to various system parameters, such as channel bandwidth and ring latency. We introduce the Dynamic Medium Access Control Mechanism (DMAC) which does not suffer from the limitations of GFM and LFM, introduces fairness in a very effective and efficient way, and is insensitive to the network parameters

Medium access control mechanisms for high speed metropolitan area networks

In this dissertation novel Medium Access Control mechanisms for High Speed Metropolitan Area networks are proposed and their performance is investigated under the presence of single and multiple priority classes of traffic. The proposed mechanisms are based on the Distributed Queue Dual Bus network, which has been adopted by the IEEE standardization committee as the 802.6 standard for Metropolitan Area Networks, and address most of its performance limitations. First, the Rotating Slot Generator scheme is introduced which uses the looped bus architecture that has been proposed for the 802.6 network. According to this scheme the responsibility for generating slots moves periodically from station to station around the loop. In this way, the positions of the stations relative to the slot generator change continuously, and therefore, there are no favorable locations on the busses. Then, two variations of a new bandwidth balancing mechanism, the NSW_BWB and ITU_NSW are introduced. Their main advantage is that their operation does not require the wastage of channel slots and for this reason they can converge very fast to the steady state, where the fair bandwidth allocation is achieved. Their performance and their ability to support multiple priority classes of traffic are thoroughly investigated. Analytic estimates for the stations\u27 throughputs and average segment delays are provided. Moreover, a novel, very effective priority mechanism is introduced which can guarantee almost immediate access for high priority traffic, regardless of the presence of lower priority traffic. Its performance is thoroughly investigated and its ability to support real time traffic, such as voice and video, is demonstrated. Finally, the performance under the presence of erasure nodes of the various mechanisms that have been proposed in this dissertation is examined and compared to the corresponding performance of the most prominent existing mechanisms

A Topology-Aware Collision Resolution Algorithm

A new collision resolution algorithm called the Space Division Multiple Access protocol (SDMA) is presented. SDMA gains a performance advantage over similar protocols by using information about the positions of stations on the network. The protocol can operate asynchrononsly on a broadcast bus, allowing variable sized packet traffic. Through simulation the protocol is demonstrated to have better performance than Ethernet and the Capetanakis Tree protocol, a similar collision resolution protocol, under some traffic conditions. In particular, under heavy loads, SDMA displays better average throughput and lower variance of delay than Ethernet. The protocol demonstrates a performance bias based on the location of stations, but in most cases this bias is less sei\u3eere than that experienced by Ethernet

Full utilization, fairness and bounded access delay on high speed bus networks

Caption title.Includes bibliographical references (p. 31-32).Supported by ARPA. MDA972-92-J-1038Angela L. Chiu, Robert G. Gallager

Fiber optic networks: fairness, access controls and prototyping

Fiber optic technologies enabling high-speed, high-capacity digital information transport have only been around for about 3 decades but in their short life have completely revolutionized global communications. To keep pace with the growing demand for digital communications and entertainment, fiber optic networks and technologies continue to grow and mature. As new applications in telecommunications, computer networking and entertainment emerge, reliability, scalability, and high Quality of Service (QoS) requirements are increasing the complexity of optical transport networks.;This dissertation is devoted to providing a discussion of existing and emerging technologies in modern optical communications networks. To this end, we first outline traditional telecommunication and data networks that enable high speed, long distance information transport. We examine various network architectures including mesh, ring and bus topologies of modern Local, Metropolitan and Wide area networks. We present some of the most successful technologies used in todays communications networks, outline their shortcomings and introduce promising new technologies to meet the demands of future transport networks.;The capacity of a single wavelength optical signal is 10 Gbps today and is likely to increase to over 100 Gbps as demonstrated in laboratory settings. In addition, Wavelength Division Multiplexing (WDM) techniques, able to support over 160 wavelengths on a single optical fiber, have effectively increased the capacity of a single optical fiber to well over 1 Tbps. However, user requirements are often of a sub-wavelength order. This mis-match between individual user requirements and single wavelength offerings necessitates bandwidth sharing mechanisms to efficiently multiplex multiple low rate streams on to high rate wavelength channels, called traffic grooming.;This dissertation examines traffic grooming in the context of circuit, packet, burst and trail switching paradigms. Of primary interest are the Media Access Control (MAC) protocols used to provide QoS and fairness in optical networks. We present a comprehensive discussion of the most recognized fairness models and MACs for ring and bus networks which lay the groundwork for the development of the Robust, Dynamic and Fair Network (RDFN) protocol for ring networks. The RDFN protocol is a novel solution to fairly share ring bandwidth for bursty asynchronous data traffic while providing bandwidth and delay guarantees for synchronous voice traffic.;We explain the light-trail (LT) architecture and technology introduced in [37] as a solution to providing high network resource utilization, seamless scalability and network transparency for metropolitan area networks. The goal of light-trails is to eliminate Optical Electronic Optical (O-E-O) conversion, minimize active switching, maximize wavelength utilization, and offer protocol and bit-rate transparency to address the growing demands placed on WDM networks. Light-trail technology is a physical layer architecture that combines commercially available optical components to allow multiple nodes along a lightpath to participate in time multiplexed communication without the need for burst or packet level switch reconfiguration. We present three medium access control protocols for light-trails that provide collision protection but do not consider fair network access. As an improvement to these light-trail MAC protocols we introduce the Token LT and light-trail Fair Access (LT-FA) MAC protocols and evaluate their performance. We illustrate how fairness is achieved and access delay guarantees are made to satisfy the bandwidth budget fairness model. The goal of light-trails and our access control solution is to combine commercially available components with emerging network technologies to provide a transparent, reliable and highly scalable communication network.;The second area of discussion in this dissertation deals with the rapid prototyping platform. We discuss how the reconfigurable rapid prototyping platform (RRPP) is being utilized to bridge the gap between academic research, education and industry. We provide details of the Real-time Radon transform and the Griffin parallel computing platform implemented using the RRPP. We discuss how the RRPP provides additional visibility to academic research initiatives and facilitates understanding of system level designs. As a proof of concept, we introduce the light-trail testbed developed at the High Speed Systems Engineering lab. We discuss how a light-trail test bed has been developed using the RRPP to provide additional insight on the real-world limitations of light-trail technology. We provide details on its operation and discuss the steps required to and decisions made to realize test-bed operation. Two applications are presented to illustrate the use of the LT-FA MAC in the test-bed and demonstrate streaming media over light-trails.;As a whole, this dissertation aims to provide a comprehensive discussion of current and future technologies and trends for optical communication networks. In addition, we provide media access control solutions for ring and bus networks to address fair resource sharing and access delay guarantees. The light-trail testbed demonstrates proof of concept and outlines system level design challenges for future optical networks

Performance Improvements for FDDI and CSMA/CD Protocols

The High-Performance Computing Initiative from the White House Office of Science and Technology Policy has defined 20 major challenges in science and engineering which are dependent on the solutions to a number of high-performance computing problems. One of the major areas of focus of this initiative is the development of gigabit rate networks to be used in environments such as the space station or a National Research and Educational Network (NREN). The strategy here is to use existing network designs as building blocks for achieving higher rates, with the ultimate goal being a gigabit rate network. Two strategies which contribute to achieving this goal are examined in detail.1 FDDI2 is a token ring network based on fiber optics capable of a 100 Mbps rate. Both media access (MAC) and physical layer modifications are considered. A method is presented which allows one to determine maximum utilization based on the token-holding timer settings. Simulation results show that employing the second counter-rotating ring in combination with destination removal has a multiplicative effect greater than the effect which either of the factors have individually on performance. Two 100 Mbps rings can handle loads in the range of 400 to 500 Mbps for traffic with a uniform distribution and fixed packet size. Performance is dependent on the number of nodes, improving as the number increases. A wide range of environments are examined to illustrate robustness, and a method of implementation is discussed