Register insertion bus architecture for fibre optic local area networks

A protocol for fibre optic local area networks, the register insertion bus (RIB), is proposed. RIB uses a folded-bus topology with an access scheme which includes the existence of two buffers in each station to hold packets that would conflict. Simulations have shown the access scheme to efficiently utilise the network with a minimum of overhead. RIB implements a fair access scheme at normal network loads but at high loads a priority scheme is implemented. An enhancement technique is discussed that will implement a fair access scheme by altering the time between transmissions based on the measured network load.<>     

A modular-network architecture for performance enhancement inextended local area network

A hierarchic-level bridged local area network (LAN) capable of interconnecting many LANs is presented. A routing strategy based on a spanning-tree-type algorithm which allows optimization of reconfiguration times, due to the possibility of selective network reconfiguration, is described. A limited extension of the filtering database is detailed. The solution enhances the standard spanning tree protocol by adding some important features which allow it to extend LAN bridging techniques to metropolitan or wider areas. The architecture is assessed using the Petri net theory. Performance indices allow assessment of mean amount of traffic lost following network reconfiguration, network availability, and network performance. The results are compared with those for a network of the same size, but managed by a standard spanning tree     

Experimental multiuser quantum key distribution network using a wavelength-addressed bus architecture

A six-user quantum key distribution network implemented on a bus topology is experimentally demonstrated. The network employs the BB84 protocol to transmit cryptographic keys encoded unto the phase states of highly attenuated laser light to distances of up to 31 km in a standard telecommunication-grade fiber. Each user on the network is assigned a unique wavelength for communication with the network server at a time. The measured quantum bit error rate and sifted key rate compare favorably with theoretical results.     

LOCNET--A local area network using optical switching

A wide-band local area network using optical switching is presently being developed by the Heinrich-Hertz-lnsitut in Berlin (West). To ensure high reliability the system will be implemented as a star type network, divided into two subsystems. All switching within the system will be done by optical switching techniques. The wide-band subsystem will use Lithium-Niobate switching matrix elements, interconnected as a multistage space switch. Thus bit rate independent channels will be available with the ability to establish various wide-band services of the in-house area. The second subsystem makes use of a single-mode star coupler. Distributed circuit switching with fast switching capability and flexible data rates will be implemented, utilizing a TDM frame, that supports 63 narrow-band connections and a capacity of 8 Mbit/s for fast data services. To prevent typical disadvantages of distributed switching like line tapping and system disturbance, caused by malfunctioning system components, LiNbO3switches will be installed in front of and behind the star coupler. The single-mode star coupler will be implemented by cascading 2 × 2 star couplers, which are available as 3-dB couplers.     

Spread spectrum fiber-optic local area network using optical processing

Spread spectrum code division multiple access (CDMA) allows asynchronous multiple access to a local area network (LAN) with no waiting. The additional bandwidth required by spread spectrum can be accommodated by using a fiber-optic channel and incoherent optical signal processing. New CDMA sequences are designed specifically for optical processing. It is shown that increasing the number of chips per bit, by using optical processing, allows an increase in capacity of a CDMA LAN. An experiment is performed demonstrating the performance of an optical CDMA LAN, operating at 100 Mbd with three users.     

A CDMA network architecture using optimized sectoring

We propose a network architecture for code-division multiple-access (CDMA) cellular systems based on adaptive sector coverage. We show that there is a capacity limit for a CDMA system, which for a soft limit is fairly hard. We also show that for nonhomogeneous traffic, changing the area of coverage for each sector in a sectored-cell can absorb the dynamics of the traffic. For a cell of a fixed radius, divided into n sectors, it is possible to select the angles of coverage of each sector in order to avoid excessive blocking due to temporary nonuniformity of traffic across the cell. This result is based on the fact that for a given set of system parameters (bandwidth, bit rates, E_b/N₀ etc.), a certain amount of area is covered. Hence, the exact shape of the cell/sector is not important. The idea presented is shown to be applicable to overlapping sectors     

利用ADSL实现局域网共享上网

ADSL采用“非对称数字用户线路”的技术，它以普通电话线路做为传输介质，具有很高的传输速率，独享带宽，安全可靠，安装快捷方便，价格实惠，上网打电话互不干扰等特点，正逐渐被人们认识和接受，应用越来越普及。目前ADSL多用于家庭上网，随着ADSL技术的不断成熟，应将ADSL的技术应用到不同的局域网网络。     

Ed-net; A multi-Protocol educational local area network

The last decade has witnessed tremendous productivity in the field of local area networks (LANs). The productivity has ranged from many different available commercial LANs to detailed technical analyses, performance evaluation models and simulation results. The need now arises for networks to teach students in university and engineers in industry how to build and design LANs. The purpose of this paper is to present the Ed-Net; a multi-protocol local area network for educational and design purposes. The network uses available VLSI chips that implement LAN protocols. The intelligent co-processors LAN controllers such as INTEL 82586 for the Ethernet and Western Digital WD 2840 for the token-passing are used. Also advanced encoder/decoder chips such as Seeq 8023 and Harris HD-6409 are utilized. Ed-Net can be configured as an Ethernet, or a tokenpassing bus. Number of experiments can be run on the network. These experiments range from: interfacing the main CPU to the LAN controller, memory sharing, FIFO and DMA operation, error detection, and synchronization to framing, data encryption and successful transmission and reception.     

Bandwidth utilization of a large local area network

DECnet Area 2, a local area network (LAN) that is part of Digital Equipment's worldwide Easynet, is described. It is comprised of several baseband Ethernet segments connected by local Ethernet repeaters and standard LAN Bridge 100 devices, which extend a LAN. Measurements carried out to determine whether the capacity of the Ethernet had been reached or exceeded are discussed. The measurements showed that the bandwidth was not reached or exceeded. They also showed that the measured traffic load and the numbers of devices connected to the Ethernet did not pose traffic throughput problems to the user community. In addition, it was found that a larger LAN configuration could be achieved by using Ethernet bridges and taking advantage of address filtering, which distributes and thus reduces traffic loads on specific segments     

A passive star-configured optical local area network using carrier sense multiple access with a novel collision detector

This work describes design and theoretical performance of a passive star-configured multimode optical fiber local area network that employs carrier sense multiple access with collision detection (CSMA/CD). We introduce a novel collision detection method that uses collision sequences constructed from cyclic error-correcting codes and a sequence weight violation rule. Each transmitter has its own unique sequence and all sequences have identical Hamming weight. The collision detection sequence is inserted in each packet header. Our method enables detection of collisions subject to a wider dynamic range variation than competing methods proposed up to now and is extremely simple. The collision detector consists of a counter which estimates the Hamming weight of the received collision detection sequence. It works both for non-return-to-zero and Manchester coding. The collision detector is analyzed for an avalanche photodiode receiver. The general performance analysis is done both with Gaussian approximations and with method of moments. A dynamic range of 17 dB seems possible for a transmitter with an extinction ratio of 100 and a simple receiver with a fixed threshold. An explicit table of 56 collision detection sequences based on the Golay code is presented.     

Optical local area network technologies

To utilize the large bandwidth of optical fiber, optical LANs must employ architectures that fundamentally differ from current single-channel LAN architectures. With computer processor speeds continuing to grow exponentially and multimedia applications growing even faster, there is a strong need for higher-speed local area networks (LANs) that can handle the traffic generated by tomorrow's LAN users. Optical fiber is well suited for high-speed traffic transport, but the busty nature of computer traffic and large number of users makes it difficult to utilize the fiber's capacity in LANs. The incorporation of multiple payload channels in future LANs is seen as a necessity; WDM is a good candidate for achieving this. The rapidly improving optical component technologies allow more flexible WDM architecture designs for various emerging applications     

Asynchronous fiber optic local area network using CDMA and optical correlation

An experimental fiber optic local area network utilizing code division multiple access (CDMA) and fiber optic delay-line signal processing is reported. The throughput-delay characteristics are compared to ALOHA and CSMA/CD. Since CDMA allows many users to access the network simultaneously, it can achieve higher throughput with no delay.     

A wireless local area network employing distributed radio bridges

This paper presents a novel distributed wireless local area network (WLAN) architecture, where each wireless terminal (WT) accesses a backbone local area network (LAN) segment via multiple radio bridges (RB's). We introduce a self-learning routing algorithm for the RB's, which automatically adapts to changes in terminal locations, and prevents multiple copies of each data frame from being forwarded over the backbone LAN segment. The distributed WLAN architecture eases the management of network topological changes and terminal mobility, compared to centralized cellular architectures. We consider the use of direct-sequence spread-spectrum (DS/SS) signaling and the slotted Aloha medium access control (MAC) protocol over the wireless links, with multiple uplink receivers and downlink transmitters at the RB's for each MAC frame. Simulation results for the uplink show that the multi-receiver site diversity and the capture effect of DS/SS signaling effectively combat multipath and multiaccess interference, resulting in high throughput capacity and stable operation for the channel. Under overload traffic, the system is able to maintain a high level of throughput with bounded delays. It is shown that the use of multiple receiver reduces the access fairness problem for WT's at different locations caused by the near-far effect.Parts of this paper were presented at IEEE Pacific Rim Conference, Victoria, B.C., May 1993, and IEEE International Conference on Selected Topics in Wireless Communications, Vancouver, B.C., June 1992. This work was partially supported by the Canadian Natural Sciences and Engineering Research Council under grant OGP-0044286.     

通过局域网透析网络安全

0 引言 随着互联网络(以下简称网络)化的普及和计算机信息化建设的飞速发展,计算机网络与日常工作、生活的每一个领域都已经密不可分,比如政府机关、学校、医院、金融、社区及家庭等等.但随之而来的是"安全",现今的安全不同往昔,随着网上银行、网上购物不断普及,网络是否安全威胁到的不只是虚幻的货币而是直接威胁到人们实质的财产.从而导致计算机网络安全受到前所未有的威胁,计算机病毒无处不在,黑客的猖獗,防不胜防.就现如今网络上存在多样的复杂的问题进行了深入探析,并提出了相应的改进和防范措施.     

Analysis of transport measurements over a local area network

Measurements of the end-of-end delay and maximum throughput are reported for a typical implementation of the bottom four layers of the Open Systems Interconnection (OSI) protocols. These comprise the transport, network, data link, and physical protocols. An overview of the four protocols is given, and the experimental environment is described. The measurement results are discussed, and some of the implementation factors that affect the performance of OSI protocols are identified     

无线局域网安全技术

简述了无线局域网安全技术的发展历程，并通过阐述有线局域网的缺点和弊端，查明了无线局域网的优势，依据无线局域网安全技术的发展历程，简要叙述并讲解了不同时期无线局域网安全领域所采用的技术，以及每一种技术的实现过程。