多约束主动路由协议及其性能分析

主动网络是一种新型的网络体系结构,能够快速地把新协议和新应用引入到正在运行的网络中。由于主动节点具有较高的计算能力,所以能够提供比传统网络更为有效的服务质量路由方案。该文尝试把服务质量路由引入到主动网络中,结合两者优点提出一种基于主动网络的多约束主动路由(MAR)协议。仿真结果表明MAR比目前其它的QoS路由机制更简洁、更灵活、更可控。     

Multicast delivery using explicit multicast over IPv6 networks

This article presents an alternative scheme, called Xcast6+, which is an extension of explicit multicast (Xcast) for an efficient delivery of multicast datagrams over IPv6 networks. The mechanism incorporates MLDv2 and a new control plane into existing Xcast6 (Xcast for IPv6) and not only does it provide the transparency of traditional multicast schemes to sources and recipients, but it also enhances the routing efficiency in networks. Since intermediate routers do not have to maintain any multicast states, it results in a more efficient and scalable mechanism to deliver traditional multicast datagrams. Furthermore, the seamless integration of Xcast6+ in Mobile IPv6 can support multicast efficiently for mobile nodes over IPv6 networks by avoiding tunnel avalanches and tunnel convergence. Our simulation results show distinct performance improvements of our approach. This approach can reduce network resources in many "medium size groups" multicast, particularly as the number of recipients in a subnet increases (i.e., "subnet-dense groups").     

Resource prediction and management in active networks

Active networks provide a programmable user–network interface that supports dynamic modification of the network's behavior. Network nodes, in addition to forwarding packets, perform customized computation on the messages flowing through them. Resources in an active network mainly consist of CPU and bandwidth. The inherent unpredictability of processing times of active packet poses a significant challenge in CPU scheduling. It has been identified that prior estimation of the resource requirements of a packet is very difficult since it is platform dependent and also depends on processing load at the time of execution, operating system scheduling, etc. An efficient allocation is required for the optimal utilization of resources. In this paper, resources are estimated using prediction techniques such as single exponential smoothing (SES), adaptive‐response‐rate single exponential smoothing (ARRSES) and Holt's two‐parameter estimation models. The estimated results agreed most with the actual requirements. The estimation models were compared with model criteria. An algorithm was also designed for the allocation of resources. Effectiveness of the algorithm was measured through simulation and achieved almost perfect fairness for all flows and also provided much superior delay guarantees under a highly dynamic environment. Copyright © 2008 John Wiley & Sons, Ltd.     

Managing QoS requirements for video streaming: from intra‐node to inter‐node

Streaming video over IP networks has become increasingly popular; however, compared to traditional data traffic, video streaming places different demands on quality of service (QoS) in a network, particularly in terms of delay, delay variation, and data loss. In response to the QoS demands of video applications, network techniques have been proposed to provide QoS within a network. Unfortunately, while efficient from a network perspective, most existing solutions have not provided end‐to‐end QoS that is satisfactory to users. In this paper, packet scheduling and end‐to‐end QoS distribution schemes are proposed to address this issue. The design and implementation of the two schemes are based on the active networking paradigm. In active networks, routers can perform user‐driven computation when forwarding packets, rather than just simple storing and forwarding packets, as in traditional networks. Both schemes thus take advantage of the capability of active networks enabling routers to adapt to the content of transmitted data and the QoS requirements of video users. In other words, packet scheduling at routers considers the correlation between video characteristics, available local resources and the resulting visual quality. The proposed QoS distribution scheme performs inter‐node adaptation, dynamically adjusting local loss constraints in response to network conditions in order to satisfy the end‐to‐end loss requirements. An active network‐based simulation shows that using QoS distribution and packet scheduling together increases the probability of meeting end‐to‐end QoS requirements of networked video. Copyright © 2005 John Wiley & Sons, Ltd.     

Cluster head election techniques for coverage preservation in wireless sensor networks

Coverage preservation is one of the basic QoS requirements of wireless sensor networks, yet this problem has not been sufficiently explored in the context of cluster-based sensor networks. Specifically, it is not known how to select the best candidates for the cluster head roles in applications that require complete coverage of the monitored area over long periods of time. In this paper, we take a unique look at the cluster head election problem, specifically concentrating on applications where the maintenance of full network coverage is the main requirement. Our approach for cluster-based network organization is based on a set of coverage-aware cost metrics that favor nodes deployed in densely populated network areas as better candidates for cluster head nodes, active sensor nodes and routers. Compared with using traditional energy-based selection methods, using coverage-aware selection of cluster head nodes, active sensor nodes and routers in a clustered sensor network increases the time during which full coverage of the monitored area can be maintained anywhere from 25% to 4.5×, depending on the application scenario.     

The Phoenix framework: a practical architecture for programmablenetworks

Programmable networks allow third parties to dynamically reprogram switches and routers in order to extend their functionality. This approach facilitates new capabilities such as dynamic reallocation of resources, automated healing from malfunctions and failures, customized information processing, and easier service creation. These capabilities enable rapid customization of the network by providing mechanisms to adapt to new applications such as multimedia, multicast, intrusion detection, and intranet firewalls. We describe Intel's framework for programmable networks, known as Phoenix. The objective of the Phoenix framework is to make it easier to deploy new network services that leverage the emerging trend toward use of reprogrammable network processors. To accomplish this goal the Phoenix framework defines an extensible mobile agent system and a set of device functionality abstractions for utilizing and extending network capabilities. We also discuss how the open interfaces provided by the Phoenix framework can be utilized to deploy new network services     

Active networks for efficient distributed network management

The emerging next generation of routers exhibit both high performance and rich functionality, such as support for virtual private networks and QoS. To achieve this, per-flow queuing and fast IP filtering are incorporated into the router hardware. The management of a network comprising such devices and efficient use of the new functionality introduce new challenges. A truly distributed network management system is an attractive candidate to address these challenges. We describe how active network techniques can be used to allow fast and easy deployment of distributed network management applications in IP networks. We describe a prototype system where legacy routers are enhanced with an adjunct active engine, which enables the safe execution and rapid deployment of new distributed management applications in the network layer. This system can gradually be integrated in today's IP network, and allows smooth migration from IP to programmable networks. This is done with an emphasis on efficient use of network resources, which is somewhat obscure by many of today's high-level solutions     

Optical services over the intelligent optical network

Optical networks are growing at unprecedented rates to accommodate the explosion in data traffic brought on by new Internet and enterprise applications. Coupled with this growth has been the introduction of client devices (e.g., routers, storage devices, and content servers) at the network edge operating at optical line rates. These two trends are changing the fundamental way in which optical transport networks are being architectured, deployed, and managed. Emerging intelligent optical networks address the traffic scaling challenge. Additionally, when combined with modern service management technologies, these networks open exciting opportunities for delivering new customized optical services directly to end-users, allowing carriers to fully exploit the economics of optical transport. This article presents a network framework for delivering optical services     

Core-stateless fair queueing: a scalable architecture to approximate fair bandwidth allocations in high-speed networks

Router mechanisms designed to achieve fair bandwidth allocations, such as fair queueing, have many desirable properties for congestion control in the Internet. However, such mechanisms usually need to maintain state, manage buffers, and/or perform packet scheduling on a per-flow basis, and this complexity may prevent them from being cost-effectively implemented and widely deployed. We propose an architecture that significantly reduces this implementation complexity yet still achieves approximately fair bandwidth allocations. We apply this approach to an island of routers - that is, a contiguous region of the network - and we distinguish between edge routers and core routers. Edge routers maintain per-flow state; they estimate the incoming rate of each flow and insert a label into each packet based on this estimate. Core routers maintain no per-flow state; they use first-in-first-out packet scheduling augmented by a probabilistic dropping algorithm that uses the packet labels and an estimate of the aggregate traffic at the router. We call the scheme core-stateless fair queueing. We present simulations and analysis on the performance of this approach.     

Accelerating hybrid and compact neural networks targeting perception and control domains with coarse-grained dataflow reconfiguration

Driven by continuous scaling of nanoscale semiconductor technologies,the past years have witnessed the progressive advancement of machine learning techniques and applications.Recently,dedicated machine learning accelerators,especially for neural networks,have attracted the research interests of computer architects and VLSI designers.State-of-the-art accelerators increase performance by deploying a huge amount of processing elements,however still face the issue of degraded resource utilization across hybrid and non-standard algorithmic kernels.In this work,we exploit the properties of important neural network kernels for both perception and control to propose a reconfigurable dataflow processor,which adjusts the patterns of data flowing,functionalities of processing elements and on-chip storages according to network kernels.In contrast to stateof-the-art fine-grained data flowing techniques,the proposed coarse-grained dataflow reconfiguration approach enables extensive sharing of computing and storage resources.Three hybrid networks for MobileNet,deep reinforcement learning and sequence classification are constructed and analyzed with customized instruction sets and toolchain.A test chip has been designed and fabricated under UMC 65 nm CMOS technology,with the measured power consumption of 7.51 mW under 100 MHz frequency on a die size of 1.8×1.8 mm^2.     

Managing IP services over a PACS Packet Network

We have developed a system and network architecture to provide IP services in the Personal Access Communications System (PACS). IP datagrams are delivered to PACS users through the PACS packet-mode data service, achieving more efficient usage of wireless resources and supporting multimedia applications such as MBone audio and video. The architecture presented in this article augments the PACS voice network with IP routers and backbone links, called the PACS Packet Network (PPN), and is connected to the global Internet via gateways. Compared to the cellular digital packet data (CDPD) network, which employs its own network-layer mobility protocol and thus supports roaming within the CDPD network only, we have incorporated Mobile IP into the PACS handoff mechanism to further achieve global IP mobility. We have also developed native PACS multicast and a group management scheme to efficiently handle dynamic IP multicast and MBone connectivity. These features seamlessly integrate PACS into the global Internet and provide standard-conforming IP services with global mobility     

大型网络中的桥接方式(1)

网桥与路由的功用是一样的,都能把数据传送到指定的目的地。可是对网络来说,选择网桥还是选择路由器的意义十分重大。由于网络用户越来越多,网桥和路由器传送数据的方式对网络的可靠性和效率有着直接的关系。为了便于说明,我们来分析一个简单的桥接网络。正如桥能把被河水隔断的一座城市连接在一起一样,网桥可以把网络的二段互连起来。来自网络一段的信息包被网桥传送到网络的另一段。     

SNMP‐based enterprise IP network topology discovery

Precise network topology information is required to perform management activities such as fault detection, root cause analysis, performance monitoring, and load balancing in enterprise networks. To accomplish these management tasks, both network discovery and connectivity information are essential. This paper examines various problems with the existing topology discovery mechanisms and proposes an SNMP‐based approach to discover physical as well as logical topology. We present algorithms for identifying network device types and discovering connectivity among them. The connectivity of end host and management information base (MIB)‐enabled devices with switches and routers is discussed and evaluated. We also present an algorithm for discovering logical topology, such as VLAN and subnet connectivity. Finally, we present a combination of graph and tree layouts, to visualize connectivity information. Copyright © 2010 John Wiley & Sons, Ltd.     

Secure quality of service handling: SQoSH

Proposals for programmable network infrastructures, such as active networks and open signaling, provide programmers with access to network resources and data structures. The motivation for providing these interfaces is accelerated introduction of new services, but exposure of the interfaces introduces many new security risks. We describe some of the security issues raised by active networks. We then describe our secure active network environment (SANE) architecture. SANE was designed as a security infrastructure for active networks, and was implemented in the SwitchWare architecture. SANE restricts the actions that loaded modules can perform by restricting the resources that can be named; this is further extended to remote invocation by means of cryptographic credentials. SANE can be extended to support restricted control of quality of service in a programmable network element. The Piglet lightweight device kernel provides a “virtual clock” type of scheduling discipline for network traffic, and exports several tuning knobs with which the clock can be adjusted. The ALIEN active loader provides safe access to these knobs to modules that operate on the network element. Thus, the proposed SQoSH architecture is able to provide safe, secure access to network resources, while allowing these resources to be managed by end users needing customized networking services. A desirable consequence of SQoSH's integration of access control and resource control is that a large class of denial-of-service attacks, unaddressed solely with access control and cryptographic protocols, can now be prevented     

Architecture for dynamic and fair distribution of bandwidth

The problem of fair distribution of available bandwidth among traffic flows or aggregates remains an essential issue in computer networks. This paper introduces a novel approach, called the E x act B andwidth D istribution S cheme (X‐BDS), for dynamic and fair distribution of available bandwidth among individual flows. In this approach, the edge routers keep per‐flow information, while the core routers maintain the aggregate flow requirements. The X‐BDS approach employs a distributed message exchange protocol for providing network feedback and for distributing aggregate flow requirements among the nodes in the network. Based on the obtained feedback, the edge routers employ the X‐BDS resource management unit to dynamically distribute available bandwidth among individual flows. The X‐BDS admission control and resource management units are responsible for fair resource allocation that supports minimum bandwidth guarantees of individual flows. This paper evaluates the Bandwidth Distribution Scheme through simulation and shows that the X‐BDS is capable of supporting per‐flow bandwidth guarantees in a dynamically changing network environment. Copyright © 2006 John Wiley & Sons, Ltd.     

A Model for Enhancing Connection Rerouting in Mobile Networks

In active networks (ANs) programs can be injected into routers and switches to extend the functionalities of the network. This allows programmers to enhance existing protocols and enables the rapid deployment of new protocols. The main objective of this paper is to show why ANs are ideal in solving the problem of connection rerouting and how current end-to-end based approaches can be enhanced. In this paper we propose a new model called active connection rerouting (ACR). In the ACR model, programs are dynamically injected into switches/routers in mobile networks to faciliate efficient connection rerouting during mobile host (MH) migration. We show how connection rerouting can be performed efficiently within the network. The ACR model uses a two stage optimization process: (i) path extension and (ii) lazy optimization. Unlike previous work on two stage connection rerouting ACR has the following properties: elimination of loops within switches/routers and incremental optimization which minimizes buffer requirements and maximized path reuse. ACR performs well in all topologies. Our experimental results show that ACR is efficient and scalable and it performs well in all topologies.     

Cooperating security managers: a peer-based intrusion detectionsystem

The need for increased security measures in computer systems and networks is apparent through the frequent media accounts of computer system and network intrusions. One attempt at increasing security measures is in the area of intrusion detection packages. These packages use a variety of means to detect intrusive activities and have been applied to both individual computer systems and networks. Cooperating security managers (CSM) is one such package. Applied to a network, CSM is designed to perform intrusion detection and reporting functions in a distributed environment without requiring a designated central site or server to perform the analysis of network audit data. In addition, it is designed to handle intrusions as opposed to simply detecting and reporting on them, resulting in a comprehensive approach to individual system and network intrusions. Tests of the initial prototype have shown the cooperative methodology to perform favourably     

Real-time payments for mobile IP

The mobile IP protocol has evolved from providing mobility support for portable computers to support for wireless handheld devices with high mobility patterns. A new category of micromobility protocols has been proposed to deal with the increased signaling loads that will be generated with large populations of such devices on a network. We argue that the authentication schemes presently employed in these networks do not scale well for large numbers of nodes, and that the lack of accounting procedures prevents the mass deployment of these networks. We envisage that future access networks will be operated by independent service providers, who will charge users for access to services in the fixed network but may not have long-term contractual relationships with them. These access networks may also employ a variety of micromobility protocols for fast handover support. We present a scheme based on hash chains, which allows for fast authentication of datagrams for secure updating of router entries within the access network, and real-time accounting of network usage by mobile nodes. Such a system will alleviate problems of fraud in mobile networks and eliminate the need for interoperator billing agreements.