Showing papers on "Heterogeneous network published in 1984"

Local network performance

Abstract: Because the number of truly different local network configurations is manageably small, a comparative analysis of local network performance is possible. The question of performance is of concern in the design. or selection of a local network for a specific application. Given a certain c,ollection of devices, with certain traffic characteristics, a fundamental requirement is that the local network has adequate capacity for the expected load. Table I, based on studies by the IEEE 802 Local Network Standards Committee, indicates the type of load that may be offered to a local network by various devices. We would like the local network to be able to sustain a throughput that keeps up with the load, and does so without undue delays. This paper aims to show which factors are significant in determining local network. performance' and to summarize recent comparative studies. The first section below shows that two basic characteristics of a local network, propagation delay and data rate, set an upper bound on performance independent of the mediumaccess control protocol. Next, some simple models are developed for comparing three protocols: CSMA/CD, token bus, and token ring. These are protocols for which standards have been developed [2], and it is likely that most local network products will use a variant of one of them. Finally, some comparative studies are summarized. The results cover CSMA/CD, token bus, and token ring, as weil as two other ring protocols slotted ring and register insertion.

A local area network architecture overview

Abstract: HIS PAPER is a brief overview of existing Local Area Network (LAN) architectures and is intended as a guide for this special issue. It begins with an attempt to define an LAN, followed by some background information on the LAN environment and user needs. To provide some technical perspective, we next compare LAN's and conventional PBX's, and then we focus on current LAN architectures and the associated protocols and technology. i An LAN is a resource-sharing data-communications network , which is limited in geographic scope to the range of 0.1-10 km, provides high bandwidth communication (above 1 Mb/s) over inexpensive transmission media, and is usually privately owned. LAN's differ from conventional long-haul networks in transmission bandwidth, network protocols, and topologies. Usually, in long-haul networks, the transmission bandwidth is expensive and network design is focused on the link utilization efficiency. Designers of LAN's, unlike designers of long-haul networks, do not consider that optimizing bandwidth use is a critical issue, since bandwidth in an LAN environment is not a precious resource [1,2]. The economic and technical characteristics of LAN's offer simple solutions for network problems. Complicated routing and control algorithms for long-haul networks are not needed for LAN's with their wide bandwidth and short-delay attributes. With their small geographic scope, any one of several different LAN topologies and resource sharing mechanisms can be selected to provide economic communications for their users. The typical environments where LAN's are applicable today include [3]: Offices where integrated voice and data communications support office automation functions such as electronic mail, text processing, document distribution, and voice storage; Universities that need to provide a communications network for accessing central or distributed processing facilities and special-purpose application software such as word processing; Factories that are increasingly moving toward automation , including automated manufacturing techniques such as CAD/CAM, robotics, and numerically controlled manufacturing processes; Laboratories that need networks to support distributed computing and distributed process control for experiments; Hospitals where communications are crucial for patient file retrieval, status monitoring, and diagnostics; Distribution and sales where communications links are needed for order entry and inventory control systems. The ,LAN's primary purpose is to provide connectivity and switching functions for premises equipment [4] (such as terminals, workstations, personal computers, and shared resources like disk storage and high-speed printers), thus allowing users to efficiently accomplish required tasks. Such tasks include accessing databases or application software residing in a mainframe, distributing files, mailing …

A new local area network architecture using a centralized bus

Abstract: LOCAL AREA NETWORKS are currently enjoying tremendous popularity as a means for providing wideband interconnection and communications among data terminals, host computers and other types of digital equipment located throughout a single building or a campus of buildings. Such networks are typically based on bus, ring, or star architectures, each of which manifests its own set of advantages and disadvantages. In this paper, an architectural approach is described that draws upon and integrates the advantages found separately in these three different architectures, while avoiding the major disadvantages found in any one. This new architecture employs a centrally located short bus that provides an extremely efficient packet-switching service to the devices attached to the network. Bandwidth on the short bus is dynamically allocated in response to instantaneous demands by means of a highly efficient but flexible prioritybased bus contention scheme. The approach permits multiple priority classes with fair allocation of bandwidth within each class, along with a capability for integrated circuit and packet switching. The architecture can also make use of existing twisted-pair building wiring, and at the same time take advantage of emerging optical-fiber technology. In addition, the architecture provides a means to expand the network beyond a local area, resulting in a wide-area network capability.

Effectiveness assessment of the metanet demonstration

Abstract: A quantitative methodology for analyzing the effectiveness of evolving systems that will undergo a series of demonstrations is presented. Emphasis is placed on the design of the demonstration by assessing the effectiveness of alternative system configurations. While the methodology has been motivated by METANET, a network of heterogeneous networks, the approach is illustrated through a simple network that consists of heterogeneous components.

An integrate aproach to a generalized computer mail in a distributed system

Abstract: This paper describes a computer mail system that solves integratetly some distributed software functions in a heterogeneous network It offers services to deliver messages between network's users (that can be people, devices, tasks or files), services to autentiphy users codes and locate facilities and services for data securing and holding distributed information coherency The implementation is distributed in the sense that there can be many “Message Proces Center” (MPC) in one or in several computers of the network, each of them controlling part of the users mailbox and allowing deliveries in the same MPC or in a diferent one The first part of this paper describes the generalized computer mail system The second part describes the algorithm to mantain a multiple-copied file distributed on several computers in the network environment