无线局域网帧数据流量研究

无线局域网中的信道要比有线局域网信道复杂的多,运载其上的流量研究成为评估和了解无线局域网行为模式的关键。比较了有线和无线局域网在体系结构和协议机制上的差异,进而分析了由于这种差异所导致的IP层数据包流量和MAC层帧数据流量不同之处,提出了无线局域网流量研究中存在的问题,探讨了无线局域网帧数据流量的研究内容和方向。     

A Unified Approach to Local Area Network Interconnection

An approach to local area network interconnection is presented Which combines the advances in static interconnection topologies, demand assignment multiple access protocols, and the availability of high-bandwidth fiber optic channels to create a cost-effective structure capable of interconnecting a large number of LAN's with heavy traffic. This approach is independent of the protocol implemented at each LAN. The structure is based on a hypercube topology where each vertex of the graph represents a LAN. Multiple access channels spanning all dimensional axes are used in this scheme. This approach is compared to a topology with direct point-to-point connections between all nodes sharing a common axis. Through the development of the degree, diameter, average distance, cost, and average packet delay, we show that using fewer high-capacity channels, a LAN interconnection network with excellent performance characteristics can be constructed, able to support a large number of LAN's with heavy traffic at a significant reduction in cost over the point-to-point case. The resulting structure has many of the desirable characteristics for static interconnection networks such as high fault tolerance, totally distributed packet routing in the interconnection network, low average distance for good performance, and low degree, resulting in low cost. For the total number of required LAN nodes and the expected amount of internode traffic, the structure is optimized for minimum cost.     

Design and evaluation of an Ethernet-based residential network

When the information superhighway arrives at the neighborhood, a residential network will connect home appliances to the community access network. These appliances include personal computers, printers, and video clients. Among all local-area network (LAN) protocols, Ethernet is the most economic and the most popular. The unique characteristics of residential networks call for new performance studies. A residential network typically has few nodes and runs different applications than business and academic LANs. Consequently, residential networks have traffic characteristics different from the subject of existing studies. We constructed a residential network testbed to collect typical application traffic statistics. Additional live traffic characterization was obtained from campus networks. Also, we investigated the suitability of Ethernet for video distribution through simulation. This paper discusses the design issues for residential networks and presents a network design that is based on Ethernet technology. Traffic models are established from the actual traffic traces and used for the performance evaluation of residential networks. Furthermore, several future data traffic scenarios are considered with bandwidth up to 6 Mb/s by scaling up current data traffic. The simulation results of the performance suggest that Ethernet can be used as a cost-effective residential network for video and data communications     

基于OPNET交换式局域网仿真建模与分析

常规局域网存在信道利用率不高、时延较大的问题,用户迫切需求使用一种方便快捷、性能良好的网络。针对这一问题,提出了常规局域网的一种改进方式---交换式局域网（ Switching LAN）。介绍了OPNET仿真软件的主要特性、建模机制及仿真步骤。采用OPNET网络仿真软件设计实验,根据2种网络特点建立不同的场景并进行仿真,并通过对比以太网时延、接收数据包流量、数据包冲突数目在不同场景时的变化,证明了交换式局域网的性能明显优于常规局域网。     

Experimental demonstration of an improved EPON architecture using OFDMA for bandwidth scalable LAN emulation

We propose and demonstrate an improved Ethernet passive optical network (EPON) architecture supporting bandwidth-scalable physical layer local area network (LAN) emulation. Due to the use of orthogonal frequency division multiple access (OFDMA) technology for the LAN traffic transmission, there is no need to change the existing EPON architecture. Only one receiver at each optical network unit (ONU) is required to detect both LAN traffic and EPON downstream traffic, which makes the proposed system simple and cost-effective. Moreover, flexible assignment of LAN traffic bandwidth is realized by allocating different number of subcarriers or using different modulation formats. The 250 Mb/s 4-quadrature amplitude modulation (4-QAM) and 500 Mb/s 16-QAM OFDM LAN traffic are successfully emulated with the EPON traffic in our experiment.     

PERFORMANCE ANALYSIS OF TRAFFIC CONTROL METHODS ON MIXED TRAFFIC CLASSES IN ATM LAN

We treat traffic control methods for the multimedia ATM LAN, in which two service classes are considered; one is for high-speed data transfer based on a fast reservation protocol (FRP service class) and the other is for the continuous bit rate (CBR) traffic such as motion video (CBR service class). Through an analytic method, the performance of the CBR service class traffic is shown to be heavily affected by the FRP service class traffic. Thus, we introduce a reserved bandwidth for the CBR service class to guarantee some appropriate level of performance for the CBR service class. With the reserved bandwidth for CBR service class, the performance of CBR service class can be preserved from being affected by the FRP class traffic load.     

File transfer in high-speed token ring networks: performanceevaluation by approximate analysis and simulation

A model of a multiple-token-ring backbone based on fiber-optic transmission, intended for LAN interconnection, is presented. Because it is one of the most important applications for inter-LAN communication, file transfer is selected for performance evaluation. A mixed traffic environment including interactive traffic is assumed. The suitability of multiple-token-access protocols is studied by approximate analysis and simulation, yielding results for both queue length and packet delay. Sensitivity with respect to medium length and station latency is considered. The results allow performance predictions for high-speed backbone networks     

Mini‐Slot‐Based Transmission Scheme for Local Customer Internetworking in PONs

We propose a new mini‐slot transmission scheme for a passive optical network (PON) in which each customer can be switched either to access mode or to internetworking mode dynamically. In this paper, we present the system implementation (called LAN‐PON) as well as the performance of the proposed transmission scheme to illustrate its feasibility and benefits. A mini‐slot scheme can rapidly reduce the queuing delay, which increases due to the flooding of the deflected packets in a deflection scheme. We evaluate the impact of mode switching time on the bandwidth gain (throughput) and delay of local area network (LAN) traffic in the LAN‐PON with a mini‐slot scheme. We also analyze a theoretical delay model of the proposed scheme. The simulation results demonstrate that switching time has an impact on LAN performance, and the average packet delay of the proposed scheme is significantly improved compared to that of the deflection scheme.     

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     

Cells-In-Frames: a system overview

Cells-In-Frames provides an efficient mechanism for integrating both voice and data traffic on an existing campus network that is currently supporting legacy LAN workstations. The solution suggested by this article is to export ATM services within standard LAN frames. Each frame will carry the traffic from one or more ATM cells, but any given LAN frame is associated with only one ATM virtual circuit. The widely different qualities of service required for voice and data traffic is achieved rough the use of AAL1 and AAL5 services. The AAL functions are split appropriately between the workstation and the LAN switch that interfaces to an ATM backbone network. With the use of the Q.2931 signalling protocols defined for ATM, Cells-in-Frames achieves a long-sought-after goal of providing switched networking services to LAN-attached workstations     

局域网流量自相似及相关性新特征分析研究

自相似业务量对计算机网络的管理和控制有着非常重要的影响。通过对一个中等规模局域网流量组成特征的分析,得出了流量组成、大小分布等特征;并通过计算流量主成分自相似参数,得出在当前网络流量组成环境下网络自相似行为新特征,确定影响自相似程度的诸多因素;通过计算诸协议间的相关性特征,得出网络流量趋势并分离出性能问题,为网络优化提供直接依据。     

Tokenless Protocols for Fiber Optic Local Area Networks

A family of LAN (Local Area Network) protocols is presented. The LAN consists of a pair of unidirectional fiber optic buses to which stations are connected via passive taps. The protocols provide round-robin bounded delay access to all stations. Contrary to most roundrobin access schemes, the protocols do not require transmission of special packets (tokens); rather, they simply rely on the detection of bus activity at each station. The performance of these protocols in various traffic conditions and system configurations is evaluated via analysis and simulation.     

Optimized routing for providing ethernet LAN services

Ethernet's-move into metropolitan and wide area networks is driving a rapidly growing market opportunity. Current Ethernet services come in two basic flavors, Ethernet line and LAN, providing point-to-point and multipoint connectivity, respectively. The LAN services, although more cost effective, are lagging behind in deployments due to associated QoS and bandwidth provisioning issues. The Ethernet service provider needs to provision the network to meet current and future traffic demands, where the traffic is unpredictable and bursty. The goal is to minimize. overprovisioning and complexity. To add to the challenge, Ethernet routing is based on simple self-learning and relies on spanning tree routing. In this article we propose an Ethernet-specific load balanced routing mechanism, which is robust to dynamic traffic demand. It significantly reduces overprovisioning, is simple and static, and requires only bandwidth profiles associated with service level agreements at the ingress and egress links. Our simulation results show that our scheme provides performance improvements over a recently proposed approach for switched Ethernet as well as a related load balancing approach for Ethernet over MPLS networks.     

Next generation local area networks

Many people now consider the local area network (LAN) to which their desktop personal computer (PC) is attached to be more important to them than the telephone network, resulting in a drive to increase both the performance and the reliability of LANs. This paper examines the key drivers for new LAN technologies, summarising LAN developments over previous years. It then looks at possible options for future LANs, which will need to evolve to meet changing traffic patterns brought about by widespread use of intranets and multimedia applications. This encompasses both new technologies such as Gigabit Ethernet, and new architectures such as virtual LANs (VLANs), multi-protocol over ATM (MPOA) and multi-protocol over LANs (MPOL).     

基于NS2的局域网路由器队列调度算法仿真分析

通过对一中等规模局域网流量分析,得出其流量组成、大小分布等特征;使用实际采集数据,用NS2模拟器模拟分析路由器在实施区分服务前后不同队列调度算法下的性能表现,发现了一些新的特征,由这些新特征可知在实际设备配置过程中,要充分考虑网络实际流量和应用需求,并非所用配置越复杂越好。     

A 622 Mb/s LAN/WAN gateway and experiences with wide area ATMnetworking

The use of similar technology in local and wide area networks enables geographically distributed high-performance applications. Key elements in achieving high performance are the appropriate use of traffic control and the development of efficient gateways between LANs and WANs. Even though the basic technology used on both sides of a gateway may be similar, the operational aspects of these elements are significantly different. A gateway has been developed and implemented not only to support communications between an ATM LAN and WAN at 622 Mb/s, but also to provide a platform for conducting network control and traffic research. In addition, the performance of the MAGIC WAN was evaluated, and bottlenecks were identified and analyzed. Techniques were developed and implemented, specifically ATM cell-level pacing, to eliminate these bottlenecks. Throughput performance close to the theoretical maximum was demonstrated. This article describes experiences with ATM over a WAN and how the gateway was developed, implemented, and evaluated. The results included show how high-speed LAN/WAN internetworking can be achieved and applied in many environments as appropriate control techniques and interfaces become ubiquitous     

基于流的校园局域网流量统计方案设计

文中系统介绍了流的概念,研究了Linux系统下基于Libpcap的流量采集原理。对校园局域网流量统计方法进行了分析,并提出了基于流的校园局域网流量统计方案,最后给出了方案的总体设计和算法实现。     

Local area network characteristics, with implications for broadbandnetwork congestion management

The authors examine the phenomenon of congestion to better understand the congestion management techniques that will be needed in high-speed, cell-based networks. The first step of this study is to use high time-resolution local area network (LAN) traffic data to explore the nature of LAN traffic variability. Then the data are used for a trace-driven simulation of a connectionless service that provides LAN interconnection. The simulation allows one to characterize what congestion might look like in a high-speed, cell-based network. When realistic data are applied to simple models of LAN interconnection, it is observed that during periods, congestion persists and losses can be significant; congestion losses cannot be avoided by modest increases in buffer capacity; consequences of misengineering can be serious; and, fortunately, most congested periods are preceded by signs of impending danger     

Embedding RMON in large LAN switches

A remote network monitoring management (RMON) agent monitors all traffic on a network segment. In a switched LAN, the only device where all traffic can be seen is the LAN switch. Thus, the most appropriate place to insert an RMON probe is in the LAN switch. In this article issues in implementing various RMON groups in a LAN switch are studied, and some approaches are proposed. The centralized solution turns out to be impractical because it is prohibitively expensive. A distributed design is presented that is suitable for implementation on multiprocessor switches. A simple analytical model is used to compare the alternatives. We investigate empirically the cost of performing typical filtering operations in an operational network. This shows that reverse filtering is often much more computationally efficient than forward filtering. We show that the distributed design can provide full RMON capability on all ports simultaneously at affordable cost     

基于自相似特性的局域网流量异常评估方法

针对现有的局域网评估模型不能提供局域网系统中数据传输安全的有效信息的缺陷,文中提出了一种通过分析局域网网关流量的自相似性变化,来对局域网系统的数据传输安全进行合理评估的方法.该方法通过选择合适的时间尺度,利用whittle估计器法计算多种测度的自相似系数,判断测度值是否偏离正常值范围来综合分析局域网流量的异常状况.在此基础上,提出了改进的局域网系统安全评估模型.实验证明,此方法能够反映网络攻击等多种原因导致的流量异常变化,提供给管理员直观的数据传输安全态势图.