基于移动代理技术的移动IP网络中链路快速建立方法

提出了一种新型移动IP漫游切换过程中链路建立方法,通过在移动主机中集成移动代理,并结合MPLS来完成链路建立时的自动信令和自主建立过程,可以改变目前移动IP网络中树状的网络体系结构,使得切换时建立新链路的信令过程大大简化,显著减小切换时延。给出了链路建立过程和性能分析,通过仿真模拟可以减少时延27%~41%。     

一种基于快速重路由的域内节能路由算法

降低互联网的能耗成为亟待解决的一个科学问题,已有的路由节能方案存在会不同程度地降低网络性能,如网络拥塞、路由振荡、路由可用性和流量分布不均匀等问题,以及需要网络的实时流量信息,从而导致算法复杂度较高的问题。设计一种基于快速重路由的绿色节能方案EEIPFRR,兼顾节能、网络性能和算法复杂度。实验结果表明,与DLF算法比较,EEIPFRR算法不仅可以降低网络能耗,并且具有较小的路径拉伸度、较低的算法复杂度和较小的最大链路利用率。     

IP protection and restoration

Protection and restoration together connote an additional layer of reliability, availability and integrity wherever they are applied. Protection ensures that the desired service will not be permanently disrupted in the event of a component failure. Restoration ensures the desired service will be returned following a component failure. For many years, IP has provided a form of protection and restoration by enabling packets to be dynamically rerouted around link or node failures. Coupled with TCP's reliable transport service, it is easy to see how TCP/IP based networking has achieved a reputation for robustness. The temporal dimension to this IP rerouting mechanism could, however, limit its usefulness for applications with real-time service-level requirements. It takes an IP network some time (usually tens of seconds) to detect a failure, propagate the information to other routers around the network, and then have each router compute a new path. The paper considers how efforts are under way in the research and vendor communities to develop faster and more robust protection and restoration mechanisms for IP networks     

网络内部链路报文丢失率的推测

提出了一种网络内部链路报文丢失率的推测方法。利用端到端测量得到的路径累积生成函数,可以推测链路的累积生成函数,从而得到链路的报文丢失率。基于链路累积生成函数保留的统计信息,运用切尔洛夫界限定理,可以判断报文丢失严重的链路,从而判断链路瓶颈。仿真实验结果验证了方法的有效性。     

IP multicast group management for point-to-point local distribution

We examine the applicability of existing IP multicast mechanisms for point-to-point links such as wired and wireless telephone lines. We identify problems such as overhead due to IGMP leave latency and unnecessary probing of hosts, both important issues for power constrained mobile hosts and low bandwidth wireless links. We propose alternative mechanisms that preserve the IP multicasting model, but employ join–leave messages to track group membership. We describe the implementation requirements of our mechanisms and compare them to existing ones with respect to performance, mobile power efficiency, interoperability, robustness and implementation complexity, demonstrating that the join–leave approach is uniformly superior for this environment.     

Fast reroute from single link and single node failures for IP multicast

The rise in multicast implementations has seen with it an increased support for fast failure recovery from link and node failures. Most recovery mechanisms augment additional services to existing protocols causing excessive overhead, and these modifications are predominantly protocol-specific. In this paper, we develop a multicast failure recovery mechanism that constructs protocol independent fast reroute paths to recover from single link and single node failures. We observe that single link failure recovery in multicast networks is similar to recovering unicast traffic, and we use existing unicast recovery mechanisms for multicast traffic. We construct multicast protection trees that provide instantaneous failure recovery from single node failures. For a given node x, the multicast protection tree spans all its neighbors and does not include itself. Thus, when the node fails, the neighbors of the node are connected through the multicast protection tree instead of node x, and forward the traffic over the multicast protection tree for the duration of failure recovery. The multicast protection trees are constructed a priori, without the knowledge of the multicast traffic in the network. Based on simulations on three realistic network topologies, we observe that the multicast protection trees increase the routing table size only by 38% on average and the path length between any source–destination pair by 13% on average.     

Autoconfiguration for IP networking: enabling local communication

IP hosts and network infrastructure have historically been difficult to configure, but emerging networking protocols promise to enable hosts to establish IP networks without prior configuration or network services. Even very simple devices with few computing resources will be able to communicate via standard protocols wherever they are attached. Current IETF (Internet Engineering Task Force) standardization efforts, such as those in the Zeroconf Working Group, aim to make this form of networking simple and inexpensive. In this tutorial, I examine the background, current status and future prospects for zero-configuration networking     

Delay and link utilization aware routing protocol for wireless multimedia sensor networks

Wireless Multimedia Sensor Networks (WMSNs) consist of networks of interconnected devices involved in retrieving multimedia content, such as, video, audio, acoustic, and scalar data, from the environment. The goal of these networks is optimized delivery of multimedia content based on quality of service (QoS) parameters, such as delay, jitter and distortion. In multimedia communications each packet has strict playout deadlines, thus late arriving packets and lost packets are treated equally. It is a challenging task to guarantee soft delay deadlines along with energy minimization, in resource constrained, high data rate WMSNs. Conventional layered approach does not provide optimal solution for guaranteeing soft delay deadlines due to the large amount of overhead involved at each layer. Cross layer approach is fast gaining popularity, due to its ability to exploit the interdependence between different layers, to guarantee QoS constraints like latency, distortion, reliability, throughput and error rate. The paper presents a channel utilization and delay aware routing (CUDAR) protocol for WMSNs. This protocol is based on a cross-layer approach, which provides soft end-to-end delay guarantees along with efficient utilization of resources. Extensive simulation analysis of CUDAR shows that it provides better delay guarantees than existing protocols and consequently reduces jitter and distortion in WMSN communication.     

太赫兹高时隙利用率快速定向MAC协议

为解决移动场景下现有定向MAC协议存在冗余单节点扇区时段分配、波束赋形训练开销过大以及用时过长等问题,提出了一种太赫兹无线个域网高时隙利用率快速定向MAC协议(High Slot Utilization Rate and FastDirectional MAC Protocol, HUFD-MAC)。HUFD-MAC协议采用冗余单节点扇区传输下行数据以及基于时间信息减少发送波束训练帧数量的机制,有效提高时隙利用率,减少网络开销,降低波束赋形用时。仿真结果表明,相比于IEEE 802. 15. 3c和ACAP-MAC协议, HUFD-MAC的网络开销降低约3. 23%, MAC层吞吐量提升约8. 50%。     

融合链接文本的增量联合主题模型*

在基于链接的概率隐含语义分析的基础上提出一种融合文本链接的增量方法进行主题建模。首先在原有网页集上进行主题建模;然后随着网页的结构和内容动态变化,利用一种合理的更新机制更新模型参数,从而高效快速地处理在线网页流的动态变化。此外,提出一个自适应非对称学习方法融合文本与链接模态的隐含主题。对于每个网页,它在两种模态上的主题分布通过加权进行融合,而权值由该网页的特征词分布的熵值确定。由于融合之后的概率结构合理地关联了链接模态和文本模态的信息,故能得到很好的建模效果。两种类型的数据集上的实验结果显示该算法可以有效地节省时间,并对网页分类有较大性能的提高,此外还提供了由本文模型生成的主题显示结果。     

A novel approach for securing IPv6 link local communication

ABSTRACT

Link local communication is one of the predominant components and intrinsic features of Internet Protocol Version 6 (IPv6) networks. IPv6 nodes utilize link local communication for ascertaining the presence of other nodes on the link, for resolving their link local addresses, and for determining the reachability information of the other nodes. To achieve link local communication, IPv6 nodes employ the services of Neighbor Discovery Protocol (NDP). The protocol also suffices and forms the fundamental core in IPv6 mobile communication, enabling multihop communication. The NDP presumes that the network consists of trusted nodes; however, with the genesis of public unsecured wireless networks, any random node with minimum authentication can affix itself to the link and launch various attacks. As in the case of NDP Stateless Address Auto Configuration (SLAAC), there is no inclusion of central address configuration servers, thereby making the process vulnerable to denial-of-service (DoS) attacks on duplicate address detection (DAD). Also, in the case of the NDP address resolution process, man-in-the-middle attacks (MITM) can be launched, whereby the attackers impersonate the legitimate nodes address. Thus access to the link can be obstructed and network traffic can be redirected without the knowledge of users. To vanquish these problems, the Internet Engineering Task Force (IETF) proposed the use of cryptographically generated addresses (CGAs), which are an intrinsic element of the Secure Neighbor Discovery (SEND) protocol. The use of CGAs ensures message integrity, authentication, and address impersonation mitigation, but at the cost of higher computation and resource utilization. This article proposes some novel approaches for securing IPv6 link layer communication operations. These techniques are implemented programmatically for securing DoS on IPv6 DAD and MITM attacks and used as an alternate approach for CGAs and the SEND protocol.     

Approximate bounds and expressions for the link utilization of shortest-path multicast network traffic

Multicast network traffic is information with one source node, but many destination nodes. Rather than setting up individual connections between the source node and each destination node, or broadcasting the information to the entire network, multicasting efficiently exploits link capacity by allowing the source node to transmit a small number of copies of the information to mutually-exclusive groups of destination nodes. Multicasting is an important topic in the fields of networking (video and audio conferencing, video on demand, local-area network interconnection) and computer architecture (cache coherency, multiprocessor message passing). In this paper, we derive approximate expressions for the minimum cost (in terms of link utilization) of shortest-path multicast traffic in arbitrary tree networks. Our results provide a theoretical best-case scenario for link utilization of multicast distribution in tree topologies overlaid onto arbitrary graphs. In real networks such as the Internet MBONE, multicast distribution paths are often tree-like, but contain some cycles for purposes of fault tolerance. We find that even for richly-connected graphs such as the shufflenet and the hypercube, our expression provides a good prediction of the cost (in terms of link utilization) of multicast communication. Thus, this theoretical result has two applications: (1) a lower bound on the link capacity required for multicasting in random tree topologies, and (2) an approximation of the cost of multicasting in regular LAN and MAN topologies.     

分布式WSN联合概率覆盖节点调度算法

利用概率覆盖探测模型,提出了一种分布式的基于联合概率覆盖的节点调度算法。节点在本地通过与其一跳邻节点的信息交互,获取本地节点所在区域的所有覆盖匹配集,根据邻节点的工作状态判断本地所在区域被概率覆盖情况;最后,节点将根据判断结果调度本地节点进入工作状态或休眠状态。仿真结果表明,该算法执行效率高于CCP和DPCP算法,能够在保证网络概率覆盖前提下,关闭大量冗余节点,保证网络工作节点数目稳定,延长了网络寿命。     

An efficient critical protection scheme for intra-domain routing using link characteristics

In recent years, there are substantial demands to reduce packet loss on the Internet. Among the proposed schemes, finding backup paths in advance is considered to be an effective method to reduce the reaction time. Very commonly, a backup path is chosen to be the most disjoint path from the primary path, or on the network level, a backup path is computed for each link (e.g., IPFRR). The validity of this straightforward choice is based on two things. The first thing is all the links may have the equal likelihood to fail; the second thing is, facing the high protection requirement today, it just looks weird to have links not protected or to share links between the primary and backup paths. Nevertheless, many studies have confirmed that the individual vulnerability of the links on the Internet is far from being equal. In addition, we have observed that full protection schemes (In this paper, full protection schemes means schemes (1) in which backup path is a most disjoint path from the primary path; or (2) which compute backup path for each link.) may introduce high cost (e.g., computation).In this paper, we argue that such approaches may not be cost-efficient and therefore propose a novel critical protection scheme based on link failure characteristics. Firstly, we analyze the link failure characteristics based on real world traces of CERNET2 (China Education and Research NETwork 2). The analysis results clearly show that the failure probabilities of the links in CERNET2 backbone are heavy-tailed, i.e., a small set of links causing most of the failures. Based on this observation, we find out two key parameters which strongly impact link criticality and propose a critical protection scheme for both single link failure situation and multi-link failure situation. We carefully analyze the implementation details and overhead for backup path schemes of the Internet today; the problem is formulated as an optimization problem to guarantee the routing performance and minimize the backup cost. This cost is special as it involves computational overhead. Based on this, we propose a novel Critical Protection Algorithm which is fast itself for both the single link failure and the multi-link failure versions. A comprehensive set of evaluations with randomly generated topologies, real world topologies and the real traces from CERNET2, shows that our scheme gains significant achievement over full protection in both single link failure situation and multi-link failure situation. It costs only about 30–60% of the full protection cost when the network relative availability increment is 90% of the full protection scheme.     

A survey of IP and multiprotocol label switching fast reroute schemes

One of the desirable features of any network is its ability to keep services running despite a link or node failure. This ability is usually referred to as network resilience and has become a key demand from service providers. Resilient networks recover from a failure by repairing themselves automatically by diverting traffic from the failed part of the network to another portion of the network. This traffic diversion process should be fast enough to ensure that the interruption of service due to a link or node failure is either unnoticeable or as small as possible. The new path taken by a diverted traffic can be computed at the time a failure occurs through a procedure called rerouting. Alternatively the path can be computed before a failure occurs through a procedure called fast reroute. Much attention is currently being paid to fast reroute because service providers who are used to the 50-ms failure recovery time associated with SONET networks are demanding the same feature from IP and MPLS networks. While this requirement can easily be met in SONET because it operates at the physical layer, it is not easily met in IP and MPLS networks that operate above the physical layer. However, over the last few years, several schemes have been proposed for accomplishing 50-ms fast reroutes for IP and MPLS networks. The purpose of this paper is to provide a survey of the IP fast reroute and MPLS fast reroute schemes that have been proposed.     

CFA local binary patterns for fast illuminant-invariant color texture classification

Journal of Real-Time Image Processing - This paper focuses on the classification of color textures acquired by single-sensor color cameras under various illuminants. Local binary patterns (LBPs)...     

Iterated fast local search algorithm for solving quadratic assignment problems

This paper concentrates on multi-row machine layout problems that can be accurately formulated as quadratic assignment problems (QAPs). A genetic algorithm-based local search approach is proposed for solving QAPs. In the proposed algorithm, three different mutation operators namely adjacent, pair-wise and insertion or sliding operators are separately combined with a local search method to form a mutation cycle. Effectiveness of introducing the mutation cycle in place of mutation is studied. Performance of the proposed iterated approach is analyzed and the solution qualities obtained are reported.     

A fast algorithm for local feature selection in data classification

Typical feature selection methods select a global feature subset that is applied over all regions of the sample space. In localized feature selection (LFS), each region of the sample space is associated with its own optimized feature subset. This allows the feature subset to adapt to local variations in the sample space. Feature subsets are selected such that within a localized region, within‐class distances are minimized and between‐class distances are maximized. LFS outperforms global feature selection methods. LFS is solved using a randomized rounding approach when weights of regions are fixed. Randomized rounding is a too time‐consuming algorithm. In this paper, we show that LFS has a closed‐form solution when weights of regions are fixed. Using this closed‐form solution can decrease the runtime of solving LFS substantially. Experimental results on real datasets confirm that the classification error rate of our proposed method and the randomized rounding‐based method are the same; the runtime of our proposed method is much better than that of the randomized rounding‐based method; and the classification error rate of our proposed method and the randomized rounding‐based method outperforms the state‐of‐the‐art feature selection methods.