Exploring High-Performance Architecture for Data Center Networks

As a critical infrastructure of cloud computing, data center networks (DCNs) directly determine the service performance of data centers, which provide computing services for various applications such as big data processing and artificial intelligence. However, current architectures of data center networks suffer from a long routing path and a low fault tolerance between source and destination servers, which is hard to satisfy the requirements of high-performance data center networks. Based on dual-port servers and Clos network structure, this paper proposed a novel architecture to construct high-performance data center networks. Logically, the proposed architecture is constructed by inserting a dual-port server into each pair of adjacent switches in the fabric of switches, where switches are connected in the form of a ring Clos structure. We describe the structural properties of in terms of network scale, bisection bandwidth, and network diameter. architecture inherits characteristics of its embedded Clos network, which can accommodate a large number of servers with a small average path length. The proposed architecture embraces a high fault tolerance, which adapts to the construction of various data center networks. For example, the average path length between servers is 3.44, and the standardized bisection bandwidth is 0.8 in (32, 5). The result of numerical experiments shows that enjoys a small average path length and a high network fault tolerance, which is essential in the construction of high-performance data center networks.     

Two secure file servers

In this paper, we describe the design and implementation of a two secure file servers which allow a trusted computer network to be built from untrusted computing bases. We begin with a brief review of recent results in the use of partial orderings for protection and administration of information networks, and introduce limited functionality, trusted computing base file servers as a means for allowing restricted information flow. We show the means by which such a server may be made provably secure. We consider the practicality of implementation and describe two prototype implementations for personal computers. We then summarizes results and point out possible extensions of this work.     

Cyclic stable matching for three-sided networking services

Three-sided relationship is very common in the social and economic area, e.g., the supplier–firm–buyer relationship, kidney exchange problem. The three-sided relationship can also be found in many scenarios of computer networking systems involving three types of agents, which we regard as three-sided networks. For example, in sensor networks, data are retrieved from data sources (sensors) and forwarded to users through a group of servers. In such three-sided networks, users always prefer to receive the best data services from data sources, data sources would choose servers that are more efficient to deliver their data, and servers try to satisfy more users. Such preferences form a specific cyclic relationship and how to optimally allocate network resources to satisfy preferences of all parties becomes a great challenge. In this paper, inspired by the three-sided stable matching, we model the Three-sided Matching with Size and Cyclic preference (TMSC) problem for data sources, servers and users, aiming to find a stable matching for them, where all their preferences are satisfied. TMSC is different from the traditional three-sided matching models, as each server may normally serve more than one users. We show that the problem of seeking an optimal stable matching with maximum cardinality is NP-hard and propose efficient algorithms for the restricted model of TMSC problem to find a stable matching. The effectiveness of the proposed algorithms is validated through extensive simulations.     

Online data storage using implicit security

It is advantageous to use implicit security for online data storage in a cloud computing environment. We describe the use of a data partitioning scheme for implementing such security involving the roots of a polynomial in finite field. The partitions are stored on randomly chosen servers on the network and they need to be retrieved to recreate the original data. Data reconstruction requires access to each server, login password and the knowledge of the servers on which the partitions are stored. This scheme may also be used for data security in sensor networks and internet voting protocols.     

Video placement and configuration of distributed video servers on cable TV networks

A large-scale, distributed video-on-demand (VOD) system allows geographically dispersed residential and business users to access video services, such as movies and other multimedia programs or documents on demand from video servers on a high-speed network. In this paper, we first demonstrate through analysis and simulation the need for a hierarchical architecture for the VOD distribution network.We then assume a hierarchical architecture, which fits the existing tree topology used in today's cable TV (CATV) hybrid fiber/coaxial (HFC) distribution networks. We develop a model for the video program placement, configuration, and performance evaluation of such systems. Our approach takes into account the user behavior, the fact that the user requests are transmitted over a shared channel before reaching the video server containing the requested program, the fact that the input/output (I/O) capacity of the video servers is the costlier resource, and finally the communication cost. In addition, our model employs batching of user requests at the video servers. We study the effect of batching on the performance of the video servers and on the quality of service (QoS) delivered to the user, and we contribute dynamic batching policies which improve server utilization, user QoS, and lower the servers' cost. The evaluation is based on an extensive analytical and simulation study.     

Discrete particle swarm optimization algorithms for two variants of the static data segment location problem

We consider the static data segment location problem in information networks. This problem was introduced by Sen et al. (Comput Oper Res, 62:282–295 2015). We consider the problem of optimally locating large volumes of digital content that is accessed via a distributed network. A database is pre-partitioned into multiple segments and the problem is one of placing these segments at servers located in different regions. We need to jointly consider four specific subproblems: (1) the problem of locating servers in the network, (2) the problem of allocating specific data segments to each of the servers, (3) the problem of assigning users to the servers based on their query patterns, and, (4) routing queries through the network. We consider two variants of this problem depending on the topology of the network through which the servers are connected: a mesh topology and a tree topology. In this paper, we develop a solution approach based on a discrete particle swarm optimization approach. We demonstrate the superiority of our approach by comparing its performance against solutions to benchmark instances obtained previously using a simulated annealing approach (Networks, 68(1):4–22 2016b).     

The MULTIBUS algorithm

Considered are product-form networks, in which some of the stations are of the MSCCC type (stations with multiple servers, in which two customers of the same group of classes cannot be served simultaneously). These networks can model parallel architectures with multiple buses. Usual product-form network algorithms do not apply to such networks, due to the complexity of the function associated to the MSCCC station. The MULTIBUS algorithm presented here yields an exact analysis of such networks.     

State diagrams and steady-state balance equations for open queuing network models

In this paper, the state diagrams and steady-state balance equations for two kinds of open queuing network models are presented. The first model comprises a network of single queues with single servers, while the second model comprises multiple servers for single queues. State diagrams are drawn for (2, 3) queuing networks with (i) single servers and (ii) multiple servers. Steady-state balance equations are derived from the state diagrams. The paper provides a method to solve open queuing networks by analyzing the stochastic process involved in the transition of states in a continuous time Markov chain which represents the state diagram of a queuing system.     

An efficient model for dimensioning an ATA-based virtual storage system

Internet Advanced Technology Attachment (iATA) is a block-level storage network protocol used by iATA servers to offer a storage solution for clients. With iATA, mobile users can access their valuable data through the network from anywhere and at anytime as if the storage device is attached locally. In the iATA architecture, iATA servers and iATA clients exchange necessary protocol messages over IP networks.     

BCDC: A High-Performance,Server-Centric Data Center Network

The capability of the data center network largely decides the performance of cloud computing. However, the number of servers in the data center network becomes increasingly huge, because of the continuous growth of the application requirements. The performance improvement of cloud computing faces great challenges of how to connect a large number of servers in building a data center network with promising performance. Traditional tree-based data center networks have issues of bandwidth bottleneck, failure of single switch, etc. Recently proposed data center networks such as DCell, FiConn, and BCube, have larger bandwidth and better fault-tolerance with respect to traditional tree-based data center networks. Nonetheless, for DCell and FiConn, the fault-tolerant length of path between servers increases in case of failure of switches; BCube requires higher performance in switches when its scale is enlarged. Based on the above considerations, we propose a new server-centric data center network, called BCDC, based on crossed cube with excellent performance. Then, we study the connectivity of BCDC networks. Furthermore, we propose communication algorithms and fault-tolerant routing algorithm of BCDC networks. Moreover, we analyze the performance and time complexities of the proposed algorithms in BCDC networks. Our research will provide the basis for design and implementation of a new family of data center networks.     

A decomposition approach to modelling high service time variability

The predictive ability of queueing network models can be greatly enhanced if these models include the effects of system characteristics such as high service time variability and simultaneous resource possession, which violate the assumptions required for their efficient exact solution. In this paper we present a new approximate solution technique for queueing networks that include Coxian servers to represent resources at which customers have high service time variability. Our approach is unique in several respects: it is based directly on the theory of near-complete decomposability, it is non-iterative (performance measures for the queueing network of interest are expressed as linear combinations of the performance measures of a set of separable queueing networks), and it is conceptually and computationally simple.     

基于用户鉴别的虚拟网络

几乎是伴随着网络的出现,许多组织就开始研究如何加强网络的安全性,以防止非法的网络入侵和访问。而除了文件服务器和大多数的应用软件早已经开始使用帐号／口令登录过程外,似乎一直没有一种真正的安全措施来保证网络资源本身的安全性。该文所探讨的基于用户鉴别的虚拟网络,就是试图通过在用户访问网络之前进行基于用户鉴别的登录,来加强的网络的安全性和可管理性。     

Circle of interacting servers: Spontaneous collective behavior in the case of large fluctuations

We consider large fluctuations and overload of servers in a network with dynamic routing of messages. The servers form a circle. The number of input flows is equal to the number of servers; the messages of a flow are distributed between two neighboring servers; upon its arrival, a message is directed to the least loaded of these servers. Under the condition that at least two servers are overloaded, the number of overloaded servers in such a network depends on the rate of input flows. In particular, there exists a critical level of the input rate above which all servers are most probably overloaded.     

移动自组网络高可用性服务的研究

Ad Hoe网络具有组网速度快、抗毁自愈能力强等优点，在军事和民用领域得到越来越广泛的应用．网络重构自恢复技术对于保证网络的可靠性、抗毁性与健壮性起着十分重要的作用．我们对Ad Hoe网络的重构自恢复进行研究，提出了一服务器组管理算法”．该算法采取主动冗余技术，通过增加、替换或删除服务器对服务器组进行维护和管理．以保证状态连续并减少服务中断，确保在提供服务的某些节点失效后整个系统仍然能够正常工作．仿真实验和数据分析表明，该算法提高了Ad Hoe网络的可用性，保证了网络的可靠性、抗毁性与健壮性．     

Optimal location query based on k nearest neighbours

Optimal location query in road networks is a basic operation in the location intelligence applications. Given a set of clients and servers on a road network, the purpose of optimal location query is to obtain a location for a new server, so that a certain objective function calculated based on the locations of clients and servers is optimal. Existing works assume no labels for servers and that a client only visits the nearest server. These assumptions are not realistic and it renders the existing work not useful in many cases. In this paper, we relax these assumptions and consider the k nearest neighbours (KNN) of clients. We introduce the problem of KNN-based optimal location query (KOLQ) which considers the k nearest servers of clients and labeled servers. We also introduce a variant problem called relocation KOLQ (RKOLQ) which aims at relocating an existing server to an optimal location. Two main analysis algorithms are proposed for these problems. Extensive experiments on the real road networks illustrate the efficiency of our proposed solutions.     

Securing UNIX-Based Networks

For many users and organizations, UNIX has become the operating system of choice for distributed systems, because of its networking capabilities and the availability of UNIX-based network protocols (e.g., TCP/IP). UNIX networks typically consist of workstations and one or more file servers linked together to form a local area network (LAN); these LANs may in turn be connected to other widely dispersed networks, thereby forming a wide area network (WAN). Protection of information on such networks can pose a serious challenge to security professionals. This article addresses the basic network security features available with most current versions of UNIX.     

Packet-switched optical networks

We describe a testbed to study both the theoretical aspects and physical implementation issues associated with high-bit-rate, multihop, packet-switched OTDM networks. We have found that using optical time-division-multiplexed (OTDM) techniques can greatly increase the bandwidth of a single-wavelength channel. Ultrafast OTDM networks are excellent candidates for meeting the system requirements for massively parallel processor interconnects, which include low latency, high bandwidth, and immunity to electromagnetic interference. High-bit-rate transparent optical networks (or TONs) for multiprocessor interconnects will be best realized with an OTDM network architecture. To fully use the bandwidth of optical fiber, we spaced the picosecond pulses closely together (about 10 ps) and typically applied a return-to-zero modulation format. While the total capacity of TDM and wavelength division multiplexing (WDM) networks may essentially be the same, TDM systems have better throughput delay performance. They also have faster, single-channel access times for high-data-rate end users such as HDTV video servers, terabyte-media data banks, and supercomputers     

Content delivery networks: status and trends

CDNs improve network performance and offer fast and reliable applications and services by distributing content to cache servers located close to users. The Web's growth has transformed communications and business services such that speed, accuracy, and availability of network-delivered content has become absolutely critical - both on their own terms and in terms of measuring Web performance. Proxy servers partially address the need for rapid content delivery by providing multiple clients with a shared cache location. In this context, if a requested object exists in a cache (and the cached version has not expired), clients get a cached copy, which typically reduces delivery time. CDNs act as trusted overlay networks that offer high-performance delivery of common Web objects, static data, and rich multimedia content by distributing content load among servers that are close to the clients. CDN benefits include reduced origin server load, reduced latency for end users, and increased throughput. CDNs can also improve Web scalability and disperse flash-crowd events. Here we offer an overview of the CDN architecture and popular CDN service providers.     

网络服务器的容错产品实例分析

本文重点分析了网络服务器的若干个容错产品的体系结构和组成等方面的容错机制。它们对于计算机网络中网络服务器、主机和通信节点机的容错设计都具有良好的参考价值。     

Measurement-based characterization and classification of QoS-enhanced systems

Quality-of-service mechanisms and differentiated service classes are increasingly available in networks and Web servers. While network and Web server clients can assess their service by measuring basic performance parameters such as packet loss and delay, such measurements do not expose the system's core QoS functionality such as multiclass service discipline. In this paper, we develop a framework and methodology for enabling network and Web server clients to assess system's multiclass mechanisms and parameters. Using hypothesis testing, maximum likelihood estimation, and empirical arrival and service rates measured across multiple time scales, we devise techniques for clients to: 1) determine the most likely service discipline among earliest deadline first, class-based weighted fair queuing, and strict priority; 2) estimate the system's parameters with high confidence; and (3) detect and parameterize non work-conserving elements such as rate limiters. We describe the important role of time scales in such a framework and identify the conditions necessary for obtaining accurate and high confidence inferences.