Stub Networks Research Articles

A 4-port flexible MIMO antenna with isolation enhancement for wireless IoT applications

This paper presents a conformal, miniaturized, and geometrically simple monopole antenna designed for Vehicle–to–Everything (V2X) communications. The antenna consists of a flexible substrate, radiating patch, ground, and metallic stubs. Meandered lines are added to the U-shaped radiator to achieve the required bandwidth of the antenna. The antenna has |S11|< −10 dB magnitude from 5.06 to 7.24 GHz, attaining a peak low magnitude of–68 dB. The antenna is configured into a 4-port Multiple–Input–Multiple–Output (MIMO) setup to minimize the mutual coupling between its elements. The proposed flexible MIMO antenna offers bandwidth from 5.37 to 7.34 GHz and a peak moderate gain of 4.63 dBi with omnidirectional stable radiation patterns. To improve the mutual coupling, two hollow concentric circular structures, in combination with a pair of stub networks are integrated between the elements of the MIMO system. The transmission coefficient and surface current analysis confirm the effectiveness of the decoupling structure. The presented MIMO antenna is characterized by high isolation, a low envelope correlation coefficient (ECC), and high diversity gain, suitable for V2X MIMO communication scenarios.

Bartolomeu: An SDN rebalancing system across multiple interdomain paths

Bartolomeu is a solution to enable stub networks to perform adaptive egress traffic load balancing across multiple interdomain routes by spreading the traffic across available paths according to a passive measurement of their performance. It defines a BGP-SDN architecture that increases the number of BGP routes that can be used by stub networks. Bartolomeu measures the available capacity of each path to any destination prefix, and allocates to each path a number of large flows that is proportional to its capacity. This strategy reduces the mean sojourn time, i.e., mean time to flow completion, compared to state-of-the-art traffic balancing techniques as ECMP. We develop a mathematical model to compute this time and compare with ECMP and single path (fast path) selection. An analysis of the traffic traces of two content providers was performed to ensure that our solution is deployable. An experiment with traffic exchange over the Internet is used to show that Bartolomeu can provide gains with real interfering traffic. A discrete-event simulator fed with the traces captured is used to asses Bartolomeu’s gains with prefixes with different number of flows, and flows with different sizes and arrival time. We observe in this experiment that Bartolomeu can reduce the sojourn time, compared to ECMP, by half when path rates differ in a factor of 3, or to a sixth when path rates differ in a factor of 10. We compute the maximum number of per-flow entries and the maximum entry change request rate to show that the resources required fit in with the specifications of the current generation of SDN switches.

High Gain Dipole Antenna with Simple Geometry and Material for Multiband Applications

In general an antenna is act as a transceiver for transmitting and receiving signals with high frequency. It is very important in real time and portable high data rate applications. The parameters decide the characterize of the antenna, the perfectness of antennae are the source resistance of the excitation source that feeds the antennae, characteristic impedance of the transmission line that feeds the antennae, the geometry of the antennae itself, the Voltage Standing Wave Ratio, the Reflection Coefficient, the Directivity, Horizontal Gain, Vertical Gain, Total Gain, radiation pattern, the magnitude of the electric field, efficiency, the current distribution and voltage distribution in the geometry of the antenna. The main parameters to be optimized for wideband portable application are the Gain, Directivity and Efficiency. Dipole antenna transmits the signal in a particular direction only. This work addresses the problem of Gain and Directivity by cascading multiple geometrical structures as well as changing the metal by which the geometrical structure is manufactured. By cascading simple structures it is possible to obtain the same directivity and gain provided by complex structures. The work identifies the second problem of efficiency by using stub or electrical networks as resonators. The stubs are designed by using impedances and admittances information provided by Smith chart at a particular frequency. The tool used for simulation is 4nec2 which stands for Numerical Electromagnetic Code. The frequency of operation used for analysis 300MHz. The wavelength in this frequency of operation is 1m.

Measuring, Characterizing, and Avoiding Spam Traffic Costs

Spam messages propagate malware, disseminate phishing exploits, and advertise illegal products. Those messages generate costs for users and network operators, but it's difficult to measure the costs associated with spam traffic and determine who actually pays for it. Here, the authors provide a method to quantify the transit costs of spam traffic, identifying the routes traversed by spam messages collected at five honeypots. Combining the volume of spam traffic with traceroute measurements and a database of internetwork business relationships, they show that stub networks are systematically subject to high spam traffic costs. They also show that some networks profit from spam traffic and might not be interested in filtering it. Finally, a simple-but-effective algorithm is presented to identify the networks that would benefit from cooperating to filter spam traffic at the origin, to reduce transit costs.

Fast Flux Watch: A mechanism for online detection of fast flux networks

Fast flux networks represent a special type of botnets that are used to provide highly available web services to a backend server, which usually hosts malicious content. Detection of fast flux networks continues to be a challenging issue because of the similar behavior between these networks and other legitimate infrastructures, such as CDNs and server farms. This paper proposes Fast Flux Watch (FF-Watch), a mechanism for online detection of fast flux agents. FF-Watch is envisioned to exist as a software agent at leaf routers that connect stub networks to the Internet. The core mechanism of FF-Watch is based on the inherent feature of fast flux networks: flux agents within stub networks take the role of relaying client requests to point-of-sale websites of spam campaigns. The main idea of FF-Watch is to correlate incoming TCP connection requests to flux agents within a stub network with outgoing TCP connection requests from the same agents to the point-of-sale website. Theoretical and traffic trace driven analysis shows that the proposed mechanism can be utilized to efficiently detect fast flux agents within a stub network.

A Study on Routing Protocol of Wireless Sensor Network

Wireless sensor network is one of the supporting technologies of the Internet of Things, composed of both communication ability and wireless sensors with limited power, WSN is responsible for sensing information and transmission of stub networks. On the basis of analyzing the reason for generating uncertain information such as information fusion and random load in wireless sensor networks, transmission model is the emphasis of research and design. Besides this, a multiple-path routing protocol with minimum transmission is put forward.

군 하이브리드 네트워크에서 생존성 향상을 위한 다중 경로 멀티캐스팅

In this paper, we propose a multi-path construction scheme to improve the survivability of a multicast session in military hybrid networks. A military hybrid network consists of a static backbone network and multiple mobile stub networks where some nodes are frequently susceptible to be disconnected due to link failure and node mobility. To improve the survivability of multicast sessions, we propose a construction scheme of <TEX>${\kappa}$</TEX> redundant multi-paths to each receiver. In order to take account of different characteristics of static and mobile networks, we propose quite different multi-path setup approaches for the backbone and stub networks, respectively, and combine them at the boundary point called gateway. We prove that our proposed scheme ensures that each receiver of a multicast session has <TEX>${\kappa}$</TEX> redundant paths to the common source. Through simulations, we evaluate the performance of the proposed schemes from three aspects : network survivability, recovery cost, and end-to-end delay.

Edge router selection and traffic engineering in LISP-capable networks

Recently, one of the problems with the Internet is the is- sue of scalability. To this end, locator/identifier separation protocol (LISP), which separates end-system identifiers and routing locators, has been proposed as a solution. In the LISP deployed network, the ingress and egress nodes of inter-AS traffic is determined by edge router selection (ERS) and endpoint identifier-routing locator mapping assignment (ERMA). In this paper, joint optimizations of ERS and ERMA for stub networks with and without pre- determined link weights are studied and the mixed integer linear programming (MILP) formulations for the problems are given. To make the problem with optimizable link weights tractable, a re- vised local search algorithm is also proposed. Simulation results show that joint optimization of ERS and ERMA enables better net- work performance.

De-ossifying internet routing through intrinsic support for end-network and ISP selfishness

We present the S4R supplemental routing system to address the constraints BGP places on ISPs and stub network alike. Technical soundness and economic viability are equal first class design requirements for S4R. In S4R, ISPs announce links connecting different parts of the Internet. ISPs can selfishly price their links to attract maximal amount of traffic. Stub networks can selfishly select paths that best meet their requirements at the lowest cost. We design a variety of practical algorithms for ISP and stub network response that strike a balance between accommodating selfishness of all participants and ensuring efficient and stable operation overall. We employ large scale simulations over realistic scenarios to show that S4R operates at a close-to-optimal state and that it encourages broad participation from stubs and ISPs.

K-Fault tolerance of the Internet AS graph

Internet disruptions such as the Northeast Blackout (2003) and the Taiwan earthquake (2006) highlight the fragility of today’s Internet. Our goal in this paper is to investigate the robustness of inter-domain communication at the level of autonomous systems (ASes), taking into account both topological connectivity and compliance to routing policies. To this end, we introduce the concept of k-fault tolerance for Type-of-Relationship (ToR) graphs, which requires that any two nodes (ASes) remain reachable from each other even after removing arbitrary k nodes from the AS graph. Our main contribution is theoretical and concerns the complexity of the k-fault tolerance decision problem. Drawing on strong evidence about the hierarchical structure of the Internet AS graph, we derive sufficient and necessary conditions for determining whether the graph is k-fault tolerant or not in polynomial time. We then apply this theoretical result to study the network-wide resilience properties of AS-level topology instances, as inferred from large-scale experimental data sets. We find that even single-node failures can disconnect up to hundred of ASes and that approximately 1500 ASes do not avail any real redundancy for their global reachability despite having two or more upstream links. Augmenting AS-level graphs for 1-fault tolerance improves overall resilience to failures, but requires a considerable number of AS-level edges (>7000) to be added. Interestingly, such additional upstream links are mainly needed at stub networks rather than at transit ASes, pointing out the need for multi-homing at stub networks.

ILBO: Balance Inbound Traffic Dynamically in Multihomed Stub Networks

Multihoming load balancing improves network performance and makes better use of network resource by leveraging the traffic among the access links in a multihomed network. Currently, no effective load balancing system is available to handle the inbound traffic in a multihomed stub network, where the traffic volume is unknown to the network and the route of the traffic is hard to control. In this paper, we propose ILBO, an inbound traffic load balancing mechanism to effectively balance the inbound traffic in a multihomed stub network. ILBO predicts and schedules the inbound traffic based on outbound traffic. It adopts a two-step traffic predictor to increase the prediction accuracy and also provides an inbound traffic control scheme that can guarantee the successful execution of the traffic scheduling. We have evaluated the effectiveness of ILBO in a trace driven simulation with real world traffic traces collected from multihomed stub networks.

Achieving Sub-50 Milliseconds Recovery Upon BGP Peering Link Failures

Recent measurements show that BGP peering links can fail as frequently as intradomain links and usually for short periods of time. We propose a new fast-reroute technique where routers are <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">prepared</i> to react quickly to interdomain link failures. For each of its interdomain links, a router precomputes a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">protection tunnel</i> , i.e., an IP tunnel to an alternate nexthop which can reach the same destinations as via the protected link. We propose a BGP- based auto-discovery technique that allows each router to learn the candidate protection tunnels for its links. Each router selects the best protection tunnels for its links and when it detects an interdomain link failure, it immediately encapsulates the packets to send them through the protection tunnel. Our solution is applicable for the links between large transit ISPs and also for the links between multi-homed stub networks and their providers. Furthermore, we show that transient forwarding loops (and thus the corresponding packet losses) can be avoided during the routing convergence that follows the deactivation of a <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">protection tunnel </i> in BGP/MPLS VPNs and in IP networks using encapsulation.

A Survey of Multihoming Technology in Stub Networks: Current Research and Open Issues

Multihoming technology can be traced back to the 1980s or even earlier, but it seldom drew much attention from the research community. Recently, with the explosive deployment of multihoming on the Internet, researchers have started to investigate the issues that were raised by multihoming networks. This article draws an overall picture of multihoming technology, presents current research on multihoming networks, and discusses the issues that must be studied in the future

Multihoming route control among a group of multihomed stub networks

In recent years, commercial “multihoming route control” devices are used by multihomed stub networks to optimize the routing of their Internet traffic. Previous studies have shown that “multihoming route control” can improve the Internet communication performance of the multihomed stub networks significantly. In this work, we study “multihoming route control” among a group of multihomed stub networks that may belong to an organization and exchange large amount of data regularly. We show that greedy “multihoming routing control” schemes could lead to oscillations. We propose a user-optimal routing based “multihoming routing control” scheme that improves routing performance without causing oscillations. The proposed scheme is simpler to implement than optimal routing based approaches. We show through simulations that the proposed scheme achieves performance close to optimal routing and works well in various network conditions.

On Global Multicast Networks Using Satellite Unidirectional Links

IP Multicast network deployment is still lagging far behind the Internet. Meanwhile, satellite links have been considered as the links that can deliver multicast traffic efficiently because of their broadcast nature. This paper analyzes the deployment of global multicast networks using satellite unidirectional links assuming that the Internet's backbone networks become the UDL feeds, and regional and stub networks become the receivers. The main objective is to understand how and how much satellite unidirectional links benefit the deployment of global multicast networks. We simulate deployment scenarios on several instances of the Internet topology taken from the RouteViews BGP routing table snapshots, where each scenario consists of UDL feeds and receivers placement strategies. The performance of each deployment scenario is measured using the multicast link count, cumulative multicast out-degree, and the expected number of downstreams per UDL receiver. Our simulations demonstrate that such a deployment gives an advantage over deployment using the existing links on the Internet.

Charging support for ad hoc stub networks

Wired equivalent security is difficult to provide in ad hoc networks due to high dynamics, wireless link vulnerability, and the requirement of complete decentralization. Especially mutual authentication among nodes in a self-organized mode of ad hoc network, where a single definition of trust is hard to build, is very difficult. This leads to several loopholes in previously established security architectures and intrusion detection systems if employed to ad hoc networks. Also, typical to ad hoc routing major security lacks are unfair participation of nodes in the system, and frequent attacks to the routing protocols by ad hoc nodes that do not want to forward foreign packets but use other nodes to forward their own packets. Contrary to detection-based approaches to tackle this situation, we propose a motivation-based approach, which does not require mutual authentication. We enable this by providing (a) a realistic architecture of ad hoc access network to an Internet Service Provider, (b) a workable business model for charging in this architecture and (c) a necessary security protocol to implement the charging scheme. For the latter we give a formal validation.

Performance evaluation of the architecture for end-to-end quality-of-service provisioning

Real-time communications services over the Internet need a new architecture to meet their required quality. From a viewpoint of quality of service provisioning architecture, the Internet can mainly be divided into three types of subnetworks: domain networks, access networks, and stub networks. In this article we focus on issues arising in the former two networks for end-to-end QoS provisioning. First, the access networks are of rather low-speed links, so delay is still of major concern. We examine the statistical delay bound through numerical results derived from our analysis. Schemes to reduce delay are proposed, and their performance is evaluated. Next, domain networks are likely to be of very high-speed links, which can accommodate a huge number of voice flows of low bit rates. Thus, effective flow management will be of major concern because per-flow management is a very costly proposition. Therefore, we pay attention to a flow aggregation scheme, and evaluate its performance by analyzing its blocking probability.

Empirically derived analytic models of wide-area TCP connections

Analyzes 3 million TCP connections that occurred during 15 wide-area traffic traces. The traces were gathered at five networks and two internetwork gateways, providing a diverse look at wide-area traffic. The author derives analytic models describing the random variables associated with TELNET, NNTP, SMTP, and FTP connections. To assess these models the author presents a quantitative methodology for comparing their effectiveness with that of empirical models such as Tcplib [Danzig and Jamin, 1991]. The methodology also allows to determine which random variables show significant variation from site to site, over time, or between stub networks and internetwork gateways. Overall the author finds that the analytic models provide good descriptions, and generally model the various distributions as well as empirical models. >