High-speed Metropolitan Area Networks Research Articles

Multicast capacity of optical ring network with hotspot traffic: The bi-directional WDM packet ring

Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic.

A single-fiber bidirectional self-healing WDM multihop mesh network with all-optical cyclic deflection routing for link restoration

In this letter, we propose and demonstrate a single-fiber bidirectional self-healing wavelength-division-multiplexing multihop mesh network architecture for high-speed metropolitan area networks. With the novel network node design, fiber link restoration is achieved by the proposed all-optical cyclic deflection routing scheme.

Dynamic p i-persistent protocol with reduced station hardware

The p i -persistent protocol has received a lot of attention from the research community and is considered to be a very suitable candidate for multiple-access communication over high-speed metropolitan area networks (MANs). The p i -persistent is a unit-capacity and distance-insensitive protocol. Further, it is a very fair protocol. In order to make the p i -persistent protocol adaptive to changing load conditions, the inventors of the protocol proposed a novel dynamic algorithm that continuously adjusts the stations' probabilities p i 's at their proper levels as governed by the offered traffic. While this dynamic algorithm achieves extremely good results, it requires N + 1 counters at the interface of each station to the network for an N-station network. Moreover, it requires a large processing time for updating the p i 's of all stations which can have a big effect on the behavior of the protocol. In this paper, we propose a variant of this dynamic algorithm that solves these two problems while yielding exactly the same results as the original algorithm. Our new algorithm requires only a constant of 4 counters per station no matter how many stations are attached to the network. Further, the processing time for updating the p i 's is a lot less than that of the original dynamic algorithm. Thus, with our new algorithm, the p i -persistent protocol seems to be the ideal candidate for future generation MANs.

ORMA: a high-performance MAC protocol for fiber-optic LANs/MANs

Emerging B-ISDN applications are accelerating the demand for high-speed and high-performance fiber optic local and metropolitan area networks (LANs and MANs). Most of the networks proposed for such an environment are based on either a folded bus or dual unidirectional bus technology, primarily due to the unidirectional nature of the fiber optic medium, their cost effectiveness, and their ability to carry asynchronous transfer mode (ATM) cells. Consequently, the design of the medium access control (MAC) protocols is the most crucial aspect for these networks since the decisions made at this level will determine the capabilities and the hardware cost of the network. The author proposes a novel MAC-layer protocol, called Optical Reservation Multiple Access (ORMA), which is suitable for data traffic on fiber optic folded bus MANs and LANs. Its main feature is an efficient optical reservation technique to allow stations to reserve transmission slots, which is attractive for use in fiber optic networks. Unlike conventional protocols. Where reservation is mostly done using software, ORMA performs its reservation using simple and effective optical circuits. Complete descriptions of the ORMA protocol and the associated nodes are given. Then the performance of ORMA is investigated as a function of the throughput, mean packet delay, and fairness among stations using analytical and simulation results. Our protocol is shown to achieve high throughput and small transmission delays while preserving the fairness of the whole network. Moreover, it compares favorably with related state-of-the-art networks. Thus, the ORMA protocol lends itself well to future-generation high-speed MANs and LANs.

The fair distributed queue (FDQ) protocol for high-speed metropolitan-area networks

A new protocol, fair distributed queue (FDQ), suitable for very high-speed metropolitan-area networks (MANs), is presented. FDQ is a slotted system implemented on a unidirectional fiber bus. It has similarities to distributed queue dual bus (DQDB), the IEEE 802.6 Standard for MANs, including the bus topology and same nodal hardware. Like DQDB, FDQ achieves full throughput efficiency independent of the bus length, the transmission speed, and the number of nodes. Unlike DQDB, FDQ allocates equal bandwidth under heavy load to all active users in a time period less than or equal to the round-trip propagation delay without wasting bandwidth. Its delay characteristics are studied via simulation and compared to DQDB. FDQ has lower average delays under Poisson load than DQDB with or without the bandwidth balancing (BWB) mechanism. Two distinct implementations of priority levels are given and their characteristics are discussed. It is shown that FDQ's delay and throughput characteristics are little affected with increasing distances or transmission rates. Thus, FDQ possesses excellent scalability properties which allow its total length to extend over 100 km and transmission rate well above 1 Gb/s.

MAC protocols and fairness control in WDM multirings with tunable transmitters and fixed receivers

The paper illustrates novel proposals for medium access control protocols in all-optical packet networks based on WDM multichannel ring topologies where nodes are equipped with one fixed-wavelength receiver and one wavelength-tunable transmitter. Such networks provide separate slotted channels for disjoint subsets of destination nodes. Three access protocols based on local status information are described. A channel inspection capability is assumed to be available for the implementation of the access protocols. Global fairness control algorithms derived from those adopted in the Metaring high-speed metropolitan area network are also proposed. Access delays and throughputs are taken as performance Indices for a simulation-based comparison of the proposed protocols, in the case of a 16-node multiring with either balanced or unbalanced traffic. Simulation results show that the throughput limitations and the fairness problems inherent in the network topology can be overcome with relatively simple protocols.

A load-controlled scheduling scheme for integrated voice-data communication on high-speed LANs/MANs

A new dynamic bandwidth-allocation (or rate-control) strategy that can be employed for integrating multimedia traffic on a class of high-speed fiber optic local and metropolitan area networks (LANs/MANs) is investigated. This new scheme is adapted from the original work by Limb on load-controlled-scheduling-of-traffic (LOCOST) mechanism, which employs channel feedback for proper distributed control operation. Although the mechanism is quite general for integrating diverse traffic types, the specific focus of this paper is on the integration of packet voice with data. The medium access control is simple, and is fully asynchronous and distributed which make it easy to implement. The necessary control functions are performed locally and independently at each data station based on a single parameter called its packet allowance, while each voice station can transmit a voice packet whenever it can. A gated global queue model is formulated to approximately analyze this system, and simulation results are also included to study the protocol's performance.

Bandwidth allocation in fair distributed queue (FDQ) networks

Fair distributed queue (FDQ) is a high speed metropolitan area network 3,5. It has been shown 3,5 that FDQ has fair throughput and delay characteristics and is a highly scalable protocol, in that its performance is little affected by growing network sizes and/or transmission speeds. FDQ allocates equal bandwidth to all active nodes. In this paper, we focus on dividing the capacity arbitrarily among the active nodes. Under heavy load, this results in nodes achieving throughput rates equal to their allocated bandwidths. Under normal load conditions, we aim to provide equal Quality of Service (QoS) to the nodes in terms of message delay, if their arrival rates turn out to be equal to their allocated bandwidths. We present the bandwidth allocation FDQ (BA-FDQ) protocol, which achieves this objective subject to propagation delays. The delay characteristics of BA-FDQ are compared via simulation with FDQ, DQDB and DQDB with BWB under symmetric load (an important special case in the absence of known arrival rates). We also consider arbitrary bandwidth allocations and study the delay characteristics of BA-FDQ by simulation. Our studies show that BA-FDQ makes the mean message delays of individual nodes close to each other (as intended) for transmission on one of the buses when the arrival rates match allocated bandwidth.

Route discovery for multistage fabrics in ATM switching nodes

This paper presents an intra-node Route Discovery Protocol (RDP) applicable to multistage switch fabrics in nodes of ATM Local Area Networks (LANs), as well as in transit nodes of future high-speed Metropolitan or Wide Area Networks (MANs or WANs). The proposed RDP automatically builds and periodically updates routing tables in each network adapter. These routing tables contain the mapping between the logical adapter addresses and the currently available physical routes through the multistage switch fabric to all other adapters attached to the node. In addition, functional entities located at specific adapters are detected and associated with physical routes in the routing tables. Detecting all routes during system startup is the basis for fast connection setup with low latency. By periodically monitoring all possible table entries, our protocol provides continuous supervision of the node's internal link status and can support possible higher-layer extensions to perform load balancing over alternative routes. Small control buffers in network adapters, which are typical for practical implementations, may lead to overflow conditions and, thus, to incompletely updated routing tables. An effective stochastic solution to this problem is presented and it will be shown through probabilistic analysis that reasonably small buffer sizes suffice for executing RDP with sufficient robustness.

An approximate performance fairness analysis of the p/sub i/-persistent protocol with destination release

Sufficient conditions are derived for achieving the two most important fairness criteria in the design of access protocols for high-speed metropolitan area networks (MAN), the delay and throughput fairness criteria, a probabilistic scheduling scheme, known as the p/sub i/-persistent protocol is considered, which has been shown to be suitable for applications requiring large bandwidth over long repeater-free distances and also amenable to an approximate analytical performance evaluation. It is found that the throughput fairness criterion is easier to achieve than its delay counterpart. The delay fairness, when achieved, induces approximate throughput fairness. The current practice in the field of protocol design for unidirectional bus MANs appears to focus almost exclusively on the throughput fairness. For example, in the DQDB protocol, although a bandwidth balancing function exists, balancing delay performance has never been dealt with.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Input rate flow control for high-speed communication networks: Blocking and delay at the access points

Abstract We present queueing models to study the system performance at the access points of a high-speed communication network. An input rate control mechanism, using a Leaky Bucket type scheme (also identified as a Credit Manager Algorithm), is applied to regulate traffic from end-user stations to the network. For the performance analysis, we select a sub-network topology which consists of a network switch (such as a fast packet or cell switch in high-speed metropolitan or wide area networks) and a number of regulated source stations. To reduce packet or cell loss probabilities at the access switch, each user station implements locally a replica of the input regulation scheme. The output traffic streams from the source stations feed into the switch, which is modeled as a multiple-server queueing system. An efficient recursive method is introduced to characterize the output traffic streams from the source stations as Markov Modulated Processes. We demonstrate the ensuing tradeoffs between message delays incurred at source stations due to the input rate control mechanism and the message delays incurred at the switch as affected by the statistical multiplexing of the input message streams. Performance curves are presented to illustrate the statistical behavior of the queue-size and message delays. Using our results, the system designer can properly select the parameters of the flow control scheme to guarantee acceptable limits of queue sizes and message delays at the source stations and at the network switches.

Media access techniques: The evolution towards terabit/s LANs and MANs

Abstract Multimedia services, teleconferencing, high-performance visualization and open-system connectivity are expected to accelerate the demand for high-speed and high-performance Local and Metropolitan Area Networks (LAN/ MANs). These must be able to span large geographical areas and to serve large populations. This paper tracks the evolution of the diverse media access techniques used in standardized, experimental and proposed networks through three technology generations. Full exploitation of technological advances has been an ongoing challenge. The first generation, which includes Ethernet, Token Ring, and Token Bus, predominantly covers bit rates of some 10 Mbit/s. The second generation comprises a large variety of network configurations and access mechanisms in the speed range from 100 Mbit/s up to multi-Gbit/s. A remarkable number of basic access schemes and numerous variations reflect the difficulty of simultaneously achieving high throughput, low delay, fairness and scalability. In the third technology generation, architectural and experimental network designs have begun taking advantage of the tremendous transmission bandwidth of more than 20 THz of the optical medium. The intent of this paper is to track this evolution, giving a concise characterization of the diverse access protocols and providing pointers to the related literature.

On the performance of topologies and access protocols for high-speed LANs and MANs

Abstract The performances of several topologies and access protocols proposed for high-speed local and metropolitan area networks (LANs and MANs) are compared using simulation models. First, FDDI (Fiber Distributed Data Interface), DQDB (Distributed Queue Dual Bus), CRMA (Cyclic Reservation Multiple Access), and CRMA-II (the latest evolution of CRMA) are compared in a uniform traffic scenario. Second, the slot reuse technique is studied for DQDB and CRMA, showing that remarkable gains in performances can be obtained, particularly in the case of non-uniform traffic distributions. Finally, meshed topologies that allow a further exploitation of spatial reuse are considered, focusing on Manhattan Street Networks (MSNs). Numerical results indicate that the massive exploitation of spatial reuse permits significant advantages in terms of user throughput and access delay to be obtained, with a node complexity comparable to that of bus or ring topologies.

The Manhattan Street Network: a high performance, highly reliable metropolitan area network

Abstract In this paper we introduce the Manhattan Street Network (MS_Net) and show it to be a strong candidate architecture for a high-speed Metropolitan Area Network (MAN). We compare the MS_Net to other MAN architectures, specifically FDDI and DQDB, and show it to be superior in terms of reliability, throughout and privacy of communications. We discuss the failure recovery mechanisms in each of these networks and their operation under multiple failures. A comparison of the throughout performance under uniform and non-uniform traffic scenarios is provided. We also compare the abilities of these three networks to provide secure service and privacy. Finally, we discuss a number of outstanding problems in the MS_Net and the proposed solutions for them.

A comparison of linear and mesh topologies-DQDB and the Manhattan street network

The authors make a performance and reliability comparison of two networks that have been proposed for use as high-speed metropolitan area networks (MANs)-the Manhattan street network (MSNet) and the distributed queue dual bus (DQDB) network. Both networks use slotted access protocols and have the same number of links, transmitters, and receivers per node. The DQDB network has been adopted by the IEEE 802.6 committee as the metropolitan area network (MAN) standard. The authors demonstrate the relative superiority of the MSNet over the DQDB network. They show that the MSNet provides a much higher network throughput for a variety of traffic patterns-uniform and nonuniform. They also look at the reliability of both networks and show that the MSNet can survive more failures than the DQDB network and that failures cause a lesser performance degradation in the MSNet. It is also shown that higher-level mechanisms are required in the DQDB network to recover from link failures whereas deflection routing is sufficient in the MSNet.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Slot reuse in MAC protocols for MAN's

Most of the medium-access control (MAC) sublayer protocols recently proposed for application in very high-speed local and metropolitan area networks (LANs and MANs) are based on a slotted transmission scheme. Slotting guarantees very good throughput efficiencies, but further gains are possible if slots can be freed after reaching their destination, thus being available for repeated use as they propagate in the network. The authors describe a simulation-based quantitative analysis of the performance gains obtained by introducing slot reuse in distributed-queue dual-bus (DQDB) and cyclic reservation multiaccess (CRMA) MANs. CRMA-II, the latest evolution of CRMA, naturally incorporates slot reuse in the MAC protocol operations and is considered in the study for comparison purposes. In the case of the standard DQDB protocol, some existing proposals are considered. In the case of CRMA, both a previous IBM proposal and a novel approach, leading to very good performances, are studied. >

Load-controlled scheduling of traffic on high-speed metropolitan area networks

An access protocol is described that is particularly appropriate for high-speed local and metropolitan area networks. It permits efficient use of the shared transmission medium, in particular where the electrical length of the medium may be many times the duration of an average packet, as well as sharing of the medium in an almost arbitrary manner among a number of competing traffic types or user classes. Each station independently measures the traffic flow on the medium and adjusts its own transmission rate according to the measured rate. The scheduling algorithm has been tested on slotted unidirectional buses and rings. By simulation the performance of the algorithm is compared to other efficient algorithms. The algorithm can control the admitted traffic of a particular type to within 2% (of full load) of the target value.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Knockout Switch for Variable-Length Packets

The Knockout Switch is a new packet switch architecture recently proposed for high-speed local and metropolitan area networks, multiprocessor interconnects, and local or toll switches for integrated traffic loads. We describe an approach to extend the original Knockout Switch to work with variable-length packets. This new architecture employs an input broadcast bus arrangement to achieve complete interconnection of the inputs and outputs. Consequently, there is no congestion in the switch fabric other than the unavoidable conflict of multiple simultaneous packets destined for the same output. It is with this output contention that the Knockout principle is fully utilized to efficiently concentrate and store contending packets while maintaining the first-in first-out discipline of the packet sequence; and yet the fabric speed required is no more than the input/output line speeds, Under these design goals, no switch can yield better delay/ throughout performance. These are the most important attributes that have been preserved in the current proposal from the original Knockout Switch. For an N \times N switch configuration, the variable-length packet Knockout Switch consists of N input broadcast buses, and an N:L concentrator ( L \ll N ) and a shared buffer for each output. The design of each subsystem is discussed with emphasis on possible VLSI realization. Using today's technology, we should be able to implement the proposed switch with both input/output lines and internal hardware operating at 50 Mbits/s. The dimension of the switch ( N \times N ) can grow modularly from say 32 × 32 to 1024 × 1024, rendering a total throughput in the range of tens of gigabits per second. Future upgrading of the line interfaces to much higher speed without modification to the internal switch hardware is also possible with a modest restriction on the minimum length of new packets.

A HIGH-Speed Packet-Switching Network for CATV Systems

A high-speed packet-switched metropolitan area network can be built on a residential cable television (CATV) system. The-goal of such a system is to extend the local area network environment from the office to the home. This paper presents an overview of communications to the home via CATV and proposes specific methods of utilizing the residential CATV system to bring high performance communication to the home.