High-performance implementation of in-network traffic pacing for small-buffer networks

Demands on data communication networks continue to drive the need for increasingly faster link speeds. Optical packet switching networks promise to provide data rates that are sufficiently high to satisfy the needs of the future Internet core network. However, a key technological problem with optical packet switching is the very small size of packet buffers that can be implemented in the optical domain. Existing protocols, for example the widely used Transmission Control Protocol (TCP), do not perform well in such small-buffer networks. To address this problem, we have proposed techniques for actively pacing traffic at edge networks to ensure that traffic bursts are reduced or eliminated and thus do not cause packet losses in routers with small buffers. We have also shown that this traffic pacing can improve the performance of conventional networks that use small buffers (e.g., to reduce the cost of buffer memory on routers). A key challenge in this context is to develop systems that can perform such packet pacing efficiently and at high data rates. In this paper, we present the design and prototype of a hardware implementation of our packet pacing technique. We discuss and evaluate design trade-offs and present performance results from an prototype implementation based on a NetFPGA fieldprogrammable gate array system. Our results show that traffic pacing can be implemented with few hardware resources and without reducing system throughput. Therefore, we believe that traffic pacing can be deployed widely to improve the operation of current and future networks.     

主动网络技术综述

Internet的迅速发展和用户需求的不断增长,使得Internet上新业务的提供成为瓶颈。主动网络的目的是让网络有计算能力,使得灵活加载新业务成为可能,这为Internet的发展开辟了新的方向。文章首先介绍了主动网络的概念与意义,然后给出了主动节点的结构以及密封囊的传输、加载和执行机制,介绍了国内外研究动态与进展。最后提出主动网络的一个实际应用。     

Traffic measurement and analysis in an ATM-based internet backbone

This paper reports our measurements and analysis of traffic characteristics in an Internet backbone ATM network. In order to utilize network resource efficiently while satisfying the quality of service requirement, it is important to understand the traffic characteristics. We therefore monitored the traffic from the flow or application level to the cell level on a link between NTT's Open Computer Network (OCN) and the Science Information Network (SINET), which are two of the largest Internet backbone ATM-based networks in Japan. Using the monitored traffic, we also evaluated the performance of the aggregate traffic by real-time simulation. Results show that the performance (cell loss ratio) greatly depended not only on link utilization but also on the number of flows, flow size, and traffic composition in terms of applications. We also found that the degree of self-similarity in the Internet backbone was not large. In addition, we clarified that more statistical multiplexing gain could be obtained in the Internet backbone when more flows were multiplexed onto a link.     

Splitting and merging of packet traffic: Measurement and modelling

This paper concerns the modelling of Internet packet traffic. In previous work we showed that a Bartlett–Lewis point process, as a model of packet arrivals on backbone links, enjoys strong physical backing and can predict key features. It is based on the surprising empirical observation that flows can often be considered independent for the purpose of modelling packet arrival times. We extend this work in two ways by using a unique dataset obtained from an experiment where all the packets crossing a backbone router are captured. First, this enables an examination of the validity of the fundamental assumptions underlying the model across several links, covering a large range of bandwidths and utilization levels. Second, we extend the model from links to a network node, by examining the merging and splitting properties of the (sub)streams through the router, and mapping these to the merging and splitting properties of the model. We show how the model can, in most cases, capture the observed multiplexing and demultiplexing behaviour of the router, opening up the possibility of its use for understanding traffic flows in networks. We show that failures in the model cannot be accounted for simply through considering utilisation levels, and explain how they can in fact be used as a detector of upstream bottlenecks and traffic shaping.     

Programming pervasive spaces

With the invention of the PC and emergence of the network, we realized we need new concepts and capabilities to program networks of computers. Standards such as TCP/IP and IEEE 802 played a major role in transforming the first computer network concept (Arpanet) to the Internet we know today. However, we also had to invent new computing models such as the client-server model, transactions, distributed objects, Web services, disconnected operation, and computing grids. Furthermore, we had to invent various middleware to support these emerging models, hiding the underlying system's complexity and presenting a more programmable view to software and application developers. Today, with the advent of sensor networks and pinhead-size computers, we're moving much closer to realizing the vision of ubiquitous and pervasive computing. However, as we create pervasive spaces, we must think ahead to consider how we program them, just as we successfully programmed the mainframe and, later on, the Internet.     

物联网中移动Sensor节点漫游的组合安全认证协议

物联网包含感知子网和传输骨干网,其感知子网中节点能力受限,往往利用移动的传感器节点跨区域访问来获取信息;而其传输骨干网络需要依托现有Internet的基础设施,并利用其提供的强大服务.在这种情况下,移动节点的漫游带来了新的安全问题,一方面移动节点在感知子网间跨区域漫游,虽和MANET中一样需要保证移动节点漫游时高效安全地加入新的拜访域,但因传感节点资源极端受限而对轻量级有更高数量级的要求;另一方面资源受限的感知子网间移动节点漫游仅能提供轻量级安全,但是在接入骨干传输网时,不可因此降低骨干网络已有的安全性,即轻量级的安全协议和传统骨干网协议综合运用时,需具有组合安全性.本文针对这种基于骨干传输网的移动节点漫游问题,提出了一个新的随机漫游认证协议(RMRAP),兼顾安全性和实际应用的可行性,实现了漫游的轻量级身份认证,保护了漫游节点的隐私,同时实现了具有前向安全性,会话密钥对;并针对衔接骨干网和感知子网的基站进行了组合安全性的认证测试,验证了RMRAP的安全性;最后,从理论分析和实验仿真两个方面,分析了RMRAP协议的性能,并和相近工作进行了对比,对比表明,具有组合安全性的RMRAP在计算、通信开销方面,依然具有和同类协议可比较的相近性能.     

Cost-effective mobile ad hoc networks management

As there are more and more mobile devices in use, different mobile networking models such as ad hoc or mesh are attracting a large research interest. Self-organizing mobile ad hoc networks (MANET) allow devices to share their services and resources without any central administration or Internet support. In this respect they can become the backbone of the wireless grid or the gateway to existing grids. To achieve these goals, MANET management must be as effective as that of wired networks. This is, however, a challenging task due to network features like mobility, heterogeneity, limited resources of hosts and feeble communication. This paper presents a set of simple, cost-effective and resilient procedures for the basic tasks of MANET creation and management.     

HSIR: hybrid architecture for sensor identification and registration for IoT applications

Internet of things is the backbone of the smart applications, which attracts many types of research on the state-of-the-art network applications. Enormous research on sensor networks left more devices that are sensible in the day-to-day life. Hence, implementing new sensor networks for smart applications is not necessary. Many researchers have accepted and utilized existing networks for their request. In this case, techniques for identifying and registering existing sensible things are on demand. This paper proposed a hybrid framework for sensor identification and registration (HSIR) for new IoT applications. This research proposing HSIR as a framework aimed for user-friendliness in the IoT as well as addressed toward the scalability requirement of IoT applications. This model uses content- and context-based multicast communication instead of broadcast to reduce energy and time consumption in sensor identification. HSIR also proposed a public key to register the new network for application requirements. The behaviour of the proposed model has been assayed in realistic with simulations and proved by comparing other models.

     

Congestion control in high-speed communication networks using the Smith principle

High-speed communication networks are characterized by large bandwidth-delay products. This may have an adverse impact on the stability of closed-loop congestion control algorithms. In this paper, classical control theory and Smith’s principle are proposed as key tools for designing an effective and simple congestion control law for high-speed data networks. Mathematical analysis shows that the proposed control law guarantees stability of network queues and full utilization of network links in a general network topology and traffic scenario during both transient and steady-state condition. In particular, no data loss is guaranteed using buffers with any capacity, whereas full utilization of links is ensured using buffers with capacity at least equal to the bandwidth-delay product. The control law is transformed to a discrete-time form and is applied to ATM networks. Moreover a comparison with the ERICA algorithm is carried out. Finally, the control law is transformed to a window form and is applied to Internet. The resulting control law surprisingly reveals that today's Transmission Control Protocol/Internet Protocol implements a Smith predictor for congestion control. This provides a theoretical insight into the congestion control mechanism of TCP/IP along with a method to modify and improve this mechanism in a way that is backward compatible.     

Hyperbolic trees for efficient routing computation

Complex system theory is increasingly applied to develop control protocols for distributed computational and networking resources. The paper deals with the important subproblem of finding complex connected structures having excellent navigability properties using limited computational resources. Recently, the two-dimensional hyperbolic space turned out to be an efficient geometry for generative models of complex networks. The networks generated using the hyperbolic metric space share their basic structural properties (like small diameter or scale-free degree distribution) with several real networks. In the paper, a new model is proposed for generating navigation trees for complex networks embedded in the two-dimensional hyperbolic plane. The generative model is not based on known hyperbolic network models: the trees are not inferred from the existing links of any network; they are generated from scratch instead and based purely on the hyperbolic coordinates of nodes. We show that these hyperbolic trees have scale-free degree distributions and are present to a large extent both in synthetic hyperbolic complex networks and real ones (Internet autonomous system topology, US flight network) embedded in the hyperbolic plane. As the main result, we show that routing on the generated hyperbolic trees is optimal in terms of total memory usage of forwarding tables.

     

IP flow identification for IP traffic carried over switched networks

Today much of the Internet backbone traffic is carried over switched networks. Switching within these backbone networks is done primarily by using permanent virtual circuits to interconnect internal routers. To improve efficiency, schemes have been suggested that involve identifying IP data flows at the edge of the switched network, and then carrying these flows over a virtual connection through the switched network. To interface with the Internet as it is today, there must be a way to identify flows that are long enough to economically warrant setting up a switched connection. Shorter flows would still be routed on a segment by segment basis. In this paper we look at the effectiveness of several flow identification algorithms, and compare them to the effectiveness of an optimum scheme. We recommend a flow definition based on client–server connections (C–S flow) that results in the lowest SVC setup rate and allows QoS to be applied based on the application.     

复杂网络研究进展:模型与应用

作为研究各种复杂系统的一种通用工具,复杂网络已经在许多学科中产生了深刻地影响,引起了各领域学者的广泛关注.本文全面地介绍复杂网络的各种主要统计特性和最具有代表性的网络模型,并且对计算机科学中关注的语言网络,Internet和P2P这些现实网络,从复杂网络的角度进行分析,展示了复杂网络理论和方法在这些领域中的应用和得到的重要结果.     

HyMN-injection-based multimedia content distribution in hybrid wireless networks

Infrastructured networks typically employ centralized approaches for group management and information provisioning. In contrast to that, in multi-hop ad hoc networks each node acts as a router as well as sender and receiver. In pure ad hoc networks, no Internet access is available. An additional challenge is to deal with mobility that causes network partitioning and re-organizations. Technically, these problems can be tackled by providing additional uplinks to a backbone network. Those can be used to access resources in the Internet as well as to inter-link multiple ad hoc network partitions, creating a hybrid wireless network. In this paper, we present HyMN, a prototypically implemented hybrid wireless network system optimized for multimedia content providing. Within the ad hoc network, adequate devices are elected to maintain uplinks to a backbone, which can provide for instance multimedia news from certain sports events like Football Championships, Olympic Games and alike. In order to efficiently manage the ad hoc communicating devices, a weighted clustering algorithm is employed. Based on an article presented at the 2nd ACM Workshop on Wireless Multimedia Networking and Performance Modeling, WMuNeP 2006, Torremolinos, Málaga, Spain, October 2006.     

Traffic engineering of MPLS backbone networks in the presence of heterogeneous streams

Heterogeneous streams (due to issues such as disparate traffic characteristics of each stream, or competing customers’ traffic) raise the issue of whether to multiplex (some of) these streams. In an MPLS network, such multiplexing can be considered by putting different streams into a tunnel identified by a single label-switched path (LSP), assuming that the different LSPs are assigned a reserved share of the resources. This issue becomes even more important in the traffic engineering of a backbone network when a decision needs to be made on which streams to multiplex when there are constraints on tunneling and capacity along with routing requirements for tunnels. In this paper, we introduce a distortion factor due to heterogeneous streams in traffic engineering of MPLS backbone networks in the presence of tunneling and capacity constraints by formulating a distortion-aware non-linear discrete optimization problem. Furthermore, we present a two-phase heuristic approach to solve this formulation efficiently. In the first phase, the problem is decoupled into two subproblems and in the second phase we show how the non-linear problem (for one of the subproblems) can be simplified. We then present numerical results for both small and large networks to show where and how our approach helps to determine when and which streams to multiplex depending on whether the tunneling and/or capacity constraint is dominant; furthermore, by comparing our distortion-aware traffic engineering model with a distortion-ignorant traffic engineering model, we show the benefits of our approach.     

实现BT数据流控制的集中管理和节点分组算法

在BitTorrent(简称BT)系统,节点利用"上行"带宽[1]来互传文件,然而这种系统中的节点之间连接所产生的数据流却消耗掉大量的主干网带宽,因此提出集中管理和节点分组(CMAPC)策略全局管理这种数据流.通过网络距离的测量,将所有节点与自己临近的节点分在一组,同组节点建立连接.实验结果显示:在不影响BT的其它性能的情况下,CMAPC能较高比例地将数据流限制在本子网中.所以得出结论:把数据流限制在本子网内来减小主干网的负载是一种较好的技术途径.     

Analysis of a rate-based feedback control strategy for long haul data transport

Digital communication has become fast enough so that the speed of light has become a bottleneck. For example, the round trip transcontinental [USA] delay through a fiber link is approximately 0.04 s; at 150 Megabit/s, a source needs to transmit approximately 8,000,000 bits during one round trip time to utilize the bandwidth fully. As the service rates of queues get large, the time scales of congestion in those queues decrease relative to the round trip time, making the dual goals of keeping buffers small and utilizations high even more difficult to achieve. In this paper we analyze a class of delayed feedback schemes that achieve these goals despite propagation delays and regardless of network rates. We analyze the delayed feedback schemes as a system of delay-differential equations, in which we model the queue-length process and the rate at which a source transmits data as fluids. We assume that a stream of acknowledgements carries information about the state of a bottleneck queue back to the source, which adapts its transmission rate according to any monotone function of that state. We show stability for this class of schemes, in that their rate of transmission and queue length rapidly converge to a small neighborhood of the designed operating point. We identify the appropriate scaling of the model's parameters, as a function of network speed, for the system to perform optimally: with a deterministic service rate of μ at the bottleneck queue, the steady state utilization of the queue is and steady state delay is . We also describe the transient of behavior of the system as another source suddenly starts competing for the bandwidth resources at the bottleneck queue. This work directly applies to the adaptive control of Frame Relay and ATM networks, both of which provide feedback to users on congestion.     

Throughput Region of Finite-Buffered Networks

Most of the current communication networks, including the Internet, are packet switched networks. One of the main reasons behind the success of packet switched networks is the possibility of performance gain due to multiplexing of network bandwidth. The multiplexing gain crucially depends on the size of the buffers available at the nodes of the network to store packets at the congested links. However, most of the previous work assumes the availability of infinite buffer-size. In this paper, we study the effect of finite buffer-size on the performance of networks of interacting queues. In particular, we study the throughput of flow-controlled loss-less networks with finite buffers. The main result of this paper is the characterization of a dynamic scheduling policy that achieves the maximal throughput with a minimal finite buffer at the internal nodes of the network under memory-less (e.g., Bernoulli IID) exogenous arrival process. However, this ideal performance policy is rather complex and, hence, difficult to implement. This leads us to the design of a simpler and possibly implementable policy. We obtain a natural trade-off between throughput and buffer-size for such implementable policy. Finally, we apply our results to packet switches with buffered crossbar architecture     

A Lagrangean Approach to Network Design Problems

Network design is a very important issue in the area of telecommunications and computer networks, where there is a large need for construction of new networks. This is due to technological development (fiber optics for telecommunication) and new ways of usage (Internet for computer networks). Optimal design of such networks requires formulation and solution of new optimization models. In this paper, we formulate several fixed charge network design models, capacitated or uncapacitated, directed or undirected, possibly with staircase costs, and survivability requirements. We propose a common solution approach for all these problems, based on Lagrangean relaxation, subgradient optimization and primal heuristics, which together form a Lagrangean heuristic. The Lagrangean heuristic can be incorporated into a branch-and-bound framework, if the exact optimal solution must be found. The approach has been tested on problems of various structures and sizes, and computational results are presented.     

Network-based multicomputers: a practical supercomputerarchitecture

Multicomputers built around a general network are an attractive architecture for a wide class of applications. The architecture provides many benefits compared with special-purpose approaches, including heterogeneity, reuse of application and system code, and sharing of resources. The architecture also poses new challenges to both computer system implementers and users. First, traditional local-area networks do not have enough bandwidth and create a communication bottleneck, thus seriously limiting the set of applications that can be run effectively. Second, programmers have to deal with large bodies of code distributed over a variety of architectures, and work in an environment where both the network and nodes are shared with other users. Our experience in the Nectar project shows that it is possible to overcome these problems. We show how networks based on high-speed crossbar switches and efficient protocol implementations can support high bandwidth and low latency communication while still enjoying the flexibility of general networks, and we use three applications to demonstrate that network-based multicomputers are a practical architecture. We also show how the network traffic generated by this new class of applications poses severe requirements for networks     

Stability Analysis of a Max-Min Fair Rate Control Protocol (RCP) in a Small Buffer Regime

In this note we analyse various stability properties of a max-min fair rate control protocol (RCP) operating with small buffers. We first tackle the issue of stability for networks with arbitrary topologies. We prove that the max-min fair RCP fluid model is globally stable in the absence of propagation delays, and also derive a set of conditions for local stability when arbitrary heterogeneous propagation delays are present. The network delay stability result assumes that, at equilibrium, there is only one bottleneck link along each route. Lastly, in the simpler setting of a single link, single delay model, we investigate the impact of the loss of local stability via a Hopf bifurcation.