Wide Area Network Environment Research Articles

User-space auto-tuning for TCP flow control in computational grids

With the advent of computational grids, networking performance over the wide-area network (WAN) has become a critical component in the grid infrastructure. Unfortunately, many high-performance grid applications only use a small fraction of their available bandwidth because operating systems and their associated protocol stacks are still tuned for yesterday's network speeds. As a result, network gurus undertake the tedious process of manually tuning system buffers to allow TCP flow control to scale to today's WAN environments. And although recent research has shown how to set the size of these system buffers automatically at connection set-up, the buffer sizes are only appropriate at the beginning of the connection's lifetime. To address these problems, we describe an automated and lightweight technique called Dynamic Right-Sizing that can improve throughput by as much as an order of magnitude while still abiding by TCP semantics. We show the performance of two user-space implementations of DRS: drsFTP and DRS-enabled GridFTP.

Operation, administration, and maintenance of Ethernet services in wide area networks

Recent developments in Ethernet technology, such as 10G Ethernet interfaces, Ethernet passive optical networks, and resilient packet rings are pushing Ethernet from the local area network environment to metropolitan and wide area network environments. For Ethernet service providers, managing Ethernet services efficiently is key to a sustainable business model. This article discusses issues in providing OAM features and capabilities to Ethernet services over metro and wide area networks. We analyze current Ethernet features that can be leveraged in an Ethernet OAM framework, and introduce requirements and new functionalities to support Ethernet services in wide area networks.

A framework of using cooperating mobile agents to achieve load sharing in distributed web server groups

This paper studies the issues of using mobile agents to achieve load sharing for network services in a wide-area network environment such as the Internet. Traditionally, load sharing algorithms are based on the message-passing paradigm. In this paper, we propose the use of mobile agents as an aid to design fully distributed and dynamic load-sharing mechanisms for wide-area network services, which provide several advantages over the pure message-passing-based approach. A framework (called MALS—mobile agent-enabled load-sharing) for structuring and designing load sharing in wide-area network services is presented. In particular, we describe the design of a mobile agent-enabled distributed dynamic load-sharing scheme within the MALS framework. A simulation environment of the load-sharing protocol is being implemented using Aglet™, a Java-compliant mobile agent platform from IBM. Preliminary experimental results demonstrated that the proposed framework is effective.

Data-centric networking using multiwavelength headers/labels in packet-over-wdm networks: a comparative study

In this paper, various issues related to packet transportation in dynamically reconfigurable networks are studied and techniques for transmitting the associated signaling are discussed. A novel transportation frame based on multisymbol coding is presented, its functionality is analyzed, and the various alternatives for transmitting multiwavelength label/headers are reviewed and benchmarked. A physical layer performance comparison between two multiwavelength schemes, i.e., the bit-parallel and the multilevel (M-ary) coded, is carried out using analytic modeling as well as simulation tools. It is shown that the multilevel coding is an interesting solution, particularly in a wide-area network environment deploying line rates higher than 10 Gb/s.

Document replication and distribution in extensible geographically distributed web servers

A geographically distributed web server (GDWS) system consists of multiple server nodes interconnected by a metropolitan area network (MAN) or a wide area network (WAN). It can achieve better efficiency in handling ever-increasing web requests than centralized web servers because its throughput will not be limited by available bandwidth connecting to a central server. The key research issue in the design of GDWS is how to replicate and distribute the documents of a website among the server nodes. This paper proposes a density-based replication scheme and applies it to our proposed Extensible GDWS architecture. We adopted a partial duplication scheme where document replication targets only at hot objects in a website. To distribute the replicas generated via the density-based replication scheme, we propose four different document distribution algorithms: Greedy-cost, Maximal-density, Greedy-penalty, and Proximity-aware. A proximity-based routing mechanism is designed to incorporate these algorithms for achieving better web server performance in a WAN environment. Simulation results show that the Greedy-penalty algorithm yields most stable load-balancing performance, and the Greedy-cost algorithm causes least internal traffic. Our scheme can achieve 80% of the performance of full-replication, with half the disk space.

An overview of the MultiMedia Communications eXchange (MMCX) and its performance characterization

MultiMedia Communications eXchange (MMCX), a new offering from Lucent Technologies, supports mixed media calling between end points on a local area network (LAN), such as Windows∗-based personal computers and any H.323 standards-compliant end point (for example, an Internet phone). The MMCX client/server architecture also provides access to the wide area network (WAN), allowing LAN end points to call users on other networks. The MMCX enables users to communicate and collaborate in a manner that best suits their needs by supporting multiparty conferencing with any type and combination of mixed media. MMCX calls can consist of any mix of voice, data, image, and video media types, with at least one of the calling/called parties directly connected to a packet transmission and/or switched network. A party to the call may be using one or more communications media, but it is not necessary for all parties on a multiparty conference call to be using the same media mix. For example, three parties may be communicating visually using LAN-connected desktop computers equipped with a videoconferencing option (audio and video), and a fourth party may be conferenced via a telephone, but he or she may only be able to speak and listen to the other parties on the call. To provide high-quality real-time mixed media collaboration in a LAN and WAN environment, important performance requirements for packet delays (such as call post-dialing delays) and media blocking must be met. This paper presents an overview of the MMCX and its performance analysis. A design tool based on our analysis has been developed to run in a PC/Windows-based environment that can be used interactively to design and reconfigure MMCX-based networks.

Limits of wide-area thin-client computing

While many application service providers have proposed using thin-client computing to deliver computational services over the Internet, little work has been done to evaluate the effectiveness of thin-client computing in a wide-area network. To assess the potential of thin-client computing in the context of future commodity high-bandwidth Internet access, we have used a novel, non-invasive slow-motion benchmarking technique to evaluate the performance of several popular thin-client computing platforms in delivering computational services cross-country over Internet2. Our results show that using thin-client computing in a wide-area network environment can deliver acceptable performance over Internet2, even when client and server are located thousands of miles apart on opposite ends of the country. However, performance varies widely among thin-client platforms and not all platforms are suitable for this environment. While many thin-client systems are touted as being bandwidth efficient, we show that network latency is often the key factor in limiting wide-area thin-client performance. Furthermore, we show that the same techniques used to improve bandwidth efficiency often result in worse overall performance in wide-area networks. We characterize and analyze the different design choices in the various thin-client platforms and explain which of these choices should be selected for supporting wide-area computing services.

Internet Resources

This project investigates the nature of electronic information available on the Internet and the problems associated with providing systematic access. By analyzing information resources, the project will (1) locate and identify types of electronic information available on the Internet, (2) produce a taxonomy of this information, and (3) assess the theoretical and applied problems libraries face in acquiring, cataloging, indexing, storing, retrieving, and disseminating this information and in providing research and reference services. The primary objective of the OCLC Internet Resources project is to analyze the textual information on the Internet to inform those interested in cataloging or otherwise describing and providing access to electronic resources in a wide-area network environment.

Teaching and learning in the wireless classroom

Wireless networks now support Web browsing, e-mail, real-time chat, and access to remote computing resources. With the increasing use of small portable computers, this emerging communications infrastructure will enable many new Internet applications. Two innovative projects at the University of North Carolina at Wilmington are currently exploring how educators can use portable handheld computers with wireless Internet access to improve teaching and learning in both local and wide area network environments.

Remote handling of TEXTOR diagnostics using CORBA as communication architecture

At the Forschungszentrum Jülich, an upgrade of the existing distributed system for data acquisition (DAS) at the fusion experiment TEXTOR94 is under development. DAS is currently restricted to VAX/VMS and DECNET based communications, but it is planned to add UNIX based systems, and to open the local network for an improved wide area network access for remote operations. Therefore, the DAS system is to be equipped with a suitable client/server interface, which is able to cope with the various computer platforms and operating systems involved. For this purpose, the common object request broker architecture (CORBA) will be used. CORBA is an object oriented, standardized architecture for distributed systems, which provides a high degree of modularity in software design and allows for flexible implementations. It is to act as a connecting link between the existing system and new extensions. In order to provide the desired client/server functionality for the data acquisition tasks, the components of the system (diagnostic, database, etc.) are modelled by CORBA interfaces. Processes for diagnostic control and data readout in the existing OpenVMS systems are aimed at to be accessible by CORBA server implementations. The corresponding client implementations will be developed for the operating system platforms most frequently used at TEXTOR94. Communication between clients and server will be based on TCP/IP and are to be managed by CORBA. By this standardized way, remote control of diagnostic instrumentation becomes possible in a multiplatform computer and wide area network environment. At a later stage it is intended to integrate the system into a ‘virtual control room’ environment, which should enable the participation of cooperating institutions in the full experimental program of TEXTOR94.

DJM: a global distributed virtual machine on the Internet

In this paper, we present the design and implementation of a novel model of distributed computing on the Internet and Intranet environment. Our model is called the Distributed Java Machine (DJM). It is a global distributed virtual machine used to realize the concept of ‘network is the computer’. DJM explores coarse-grained parallelism by using the under-utilized workstations on the network, combining the elements of object-oriented technology, distributed computing, World-Wide Web and Java programming. It can run on machines with heterogeneous hardware and software platforms without relinking or recompilation. DJM has two unique features. First, using an original applet helper mechanism, DJM allows machines without any DJM software and of different levels of ‘trust’ to work together. Secondly, DJM has implemented concurrency enhancement mechanisms (one-way message, future and redirected future) to increase the efficiency of method invocation. The prototype of DJM has been implemented and tested under both the Intranet and the Internet environments. Using the workstations from our teaching laboratories, which are already running under normal loading, experimental results show that we can achieve a speedup of about 5–8 times by 14 workstations in a Local Area Network (LAN) environment, and about 4.5 times speedup for eight workstations in a Wide Area Network (WAN) environment. © 1998 John Wiley & Sons, Ltd.

Characteristics of ABR explicit rate control algorithms in WAN environments and an ABR control algorithm suitable for public networks

This paper investigates the characteristics of available bit rate (ABR) explicit rate control algorithms in wide area network (WAN) environments. An ABR service is expected to make more effective bandwidth utilization possible through closed loop congestion control, and several control algorithms have been proposed. However, in WAN environments a long propagation control delay will affect the effectiveness of the control algorithms. Additionally, if a network supports a large number of connections, some of the algorithms may not work well. Thus we have categorized the control algorithms according to their purpose and mechanism and have evaluated their characteristics by simulation in WAN environments from the viewpoint of throughput, robustness, quickness, stability and fairness. Based on this analysis, we have developed an ABR control algorithm suitable for public networks. © 1998 John Wiley & Sons, Ltd.

Experiences with multimedia applications over native ATM

Asynchronous transfer mode (ATM) is a high-speed networking technology that has gained wide acceptance for wide area and local area network environments. In the last few years, many applications have been deployed to run over ATM. However, most of these implementations use TCP or UDP as transport layers, with IP-over-ATM providing the network layer. Real desktop multimedia applications running over native ATM are yet to be deployed. In this paper, we present raw data performance results for TCP-UDP/IP and native ATM on Windows NT 4.0. We also describe our performance experiences with native ATM implementations of multimedia applications such as video conferencing and medical visualization. Finally, we demonstrate the benefit of native ATM over TCP/IP on quality of service (QoS) parameters such as jitter, in cases when multiple multimedia applications run concurrently. It is hoped that the lessons and experiences gained will be useful to designers and implementers of native ATM services on popular operating system platforms such as Windows NT 4.0.1998 Academic Press

Effective control of traffic flow in ATM networks using fuzzy explicit rate marking (FERM)

We describe the fuzzy explicit fate marking (FERM) traffic flow control algorithm for a class of best effort service, known as available bit rate (ABR), proposed by the ATM Forum. FERM is an explicit rate marking scheme in which an explicit rate is calculated at the asynchronous transfer mode (ATM) switch and sent back to the ABR traffic sources encapsulated within resource management (RM) cells. The flow rate is calculated by the fuzzy congestion control (FCC) module by monitoring the average ABR queue length and its rate of change, then by using a set of linguistic rules. We use simulation to compare the steady-state and transient performance of FERM with EPRCA (a current favourite by the ATM Forum) in the presence of high priority variable bit rate (VBR) video and constant bit rate (CBR) in both a local-area network (LAN) and a wide-area network (WAN) environment. Our experiments show that FERM exhibits a robust behavior, even under extreme network loading conditions, and ensures fair share of the bandwidth for all virtual channels (VCs) regardless of the number of hops they traverse. Additionally, FERM controls congestion substantially better than EPRCA, offers faster transient response, leads to lower end-to-end delay and better network utilization.

ATM WAN performance tools, experiments, and results

Practical experiments in a wide-area ATM network environment are essential to gain a better understanding of the factors affecting ATM performance. This article summarizes the main lessons learned through the authors' practical experiences with ATM and how these can be applied to performance tuning. In order to achieve maximum performance from an ATM WAN, factors ranging from the transport protocol to the equipment used and the network conditions must be carefully taken into consideration. The authors also discuss some of the software-based throughput measurement tools available for the evaluation of high speed network performance, with particular emphasis on NetSpec.

Mariposa: a wide-area distributed database system

The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS.In this world, a single program performing global query optimization using a cost-based optimizer will not work well. Cost-based optimization does not respond well to site-specific type extension, access constraints, charging algorithms, and time-of-day constraints. Furthermore, traditional cost-based distributed optimizers do not scale well to a large number of possible processing sites. Since traditional distributed DBMSs have all used cost-based optimizers, they are not appropriate in a WAN environment, and a new architecture is required.We have proposed and implemented an economic paradigm as the solution to these issues in a new distributed DBMS called Mariposa. In this paper, we present the architecture and implementation of Mariposa and discuss early feedback on its operating characteristics.

A multimedia synchronization model and its implementation in transport protocols

An implementation of a synchronization mechanism in transport protocol to support multimedia applications over a packet or cell switched network is proposed. In designing such a mechanism for practical use, ease of implementation and capability of handling random delay of packets are two key issues for success. Since the random delay of packet or cell switched networks makes synchronization among media more complicated after the transmission across the network, a model which considers the random transmission delay is hence required to specify the temporal relationship among media. Therefore, a real-time synchronization model is presented to satisfy this requirement in the paper. Based on the proposed synchronization model, a transport protocol, namely the multimedia synchronization transport protocol (MSTP), is designed and implemented. We have implemented a prototype system using the MSTP protocol and built a simulation system for the wide area network (WAN) environment in order to evaluate the performance of the MSTP protocol.

Host migration transparency in IP networks

Increasing portability of computers will require users in the future to access the network regardless of location. Host migration transparency will be an essential feature of wide area network environments. We proposed the concept of virtual network and the propagating cache method to achieve host migration transparency [12]. We also established the feasibility of Virtual Internet Protocol (VIP), derived from Internet Protocol (IP), as an example of a virtual network protocol. In this paper, we define VIP in detail and describe how VIP achieves host migration transparency in IP networks. We also show two VIP implementation approaches: 1) VIP as a sublayer; and 2) VIP as an IP option. By modifying an operating systems kernel in each case, we implement VIP using both approaches. We then compare both implementations in terms of overhead, backward compatibility, and other metrics. The measured performance indicates that VIP can provide host migration transparency in IP networks with negligible overhead.

Control of resources in broadband networks with quality of service guarantees

The design principles of resource control algorithms based on asynchronous time-sharing (ATS) are addressed, together with their interaction and cooperation in a wide area network environment, and a framework for evaluating the overall performance of the system is presented. The basic concepts of the ATS framework are presented, along with an overview of an architecture for joint scheduling and admission control. Scheduling mediates the low-level competition for service between cells of different classes; admission control regulates the acceptance or blocking of incoming traffic on a call-by-call basis. The performance of the scheduling algorithms is evaluated and the interaction between scheduling and admission control is quantified. A reference model for broadband networks is presented. >