Showing papers on "Packet loss published in 2007"

Contention Resolution Diversity Slotted ALOHA (CRDSA): An Enhanced Random Access Schemefor Satellite Access Packet Networks

Abstract: In this paper a new multiple access scheme dubbed contention resolution diversity slotted ALOHA (CRDSA) is introduced and its performance and implementation are thoroughly analyzed. The scheme combines diversity transmission of data bursts with efficient interference cancellation techniques. It is shown that CRDSA largely outperforms the classical lotted ALOHA (SA) technique in terms of throughput under equal packet loss ratio conditions (e.g. 17-fold improvement at packet loss ratio = 2 middot 10-2). CRDSA allows to boost the performance of random access (RA) channels in the return link of interactive satellite networks, making RA very efficient and providing low latency for the transmission of small size sparse packets. Implementation-wise it is shown that the CRDSA technique can be easily integrated in systems equipped with digital burst demodulators.

Robust $H_{\infty}$ Control for Networked Systems With Random Packet Losses

Abstract: In this paper, the robust Hinfin control problem Is considered for a class of networked systems with random communication packet losses. Because of the limited bandwidth of the channels, such random packet losses could occur, simultaneously, in the communication channels from the sensor to the controller and from the controller to the actuator. The random packet loss is assumed to obey the Bernoulli random binary distribution, and the parameter uncertainties are norm-bounded and enter into both the system and output matrices. In the presence of random packet losses, an observer-based feedback controller is designed to robustly exponentially stabilize the networked system in the sense of mean square and also achieve the prescribed Hinfin disturbance-rejection-attenuation level. Both the stability-analysis and controller-synthesis problems are thoroughly investigated. It is shown that the controller-design problem under consideration is solvable if certain linear matrix inequalities (LMIs) are feasible. A simulation example is exploited to demonstrate the effectiveness of the proposed LMI approach.

Characterizing residential broadband networks

Abstract: A large and rapidly growing proportion of users connect to the Internet via residential broadband networks such as Digital Subscriber Lines (DSL) and cable. Residential networks are often the bottleneck in the last mile of today's Internet. Their characteristics critically affect Internet applications, including voice-over-IP, online games, and peer-to-peer content sharing/delivery systems. However, to date, few studies have investigated commercial broadband deployments, and rigorous measurement data that characterize these networks at scale are lacking.In this paper, we present the first large-scale measurement study of major cable and DSL providers in North America and Europe. We describe and evaluate the measurement tools we developed for this purpose. Our study characterizes several properties of broadband networks, including link capacities, packet round-trip times and jitter, packet loss rates, queue lengths, and queue drop policies. Our analysis reveals important ways in which residential networks differ from how the Internet is conventionally thought to operate. We also discuss the implications of our findings for many emerging protocols and systems, including delay-based congestion control (e.g., PCP) and network coordinate systems (e.g., Vivaldi).

Upstream congestion control in wireless sensor networks through cross-layer optimization

Abstract: Congestion in wireless sensor networks not only causes packet loss, but also leads to excessive energy consumption. Therefore congestion in WSNs needs to be controlled in order to prolong system lifetime. In addition, this is also necessary to improve fairness and provide better quality of service (QoS), which is required by multimedia applications in wireless multimedia sensor networks. In this paper, we propose a novel upstream congestion control protocol for WSNs, called priority-based congestion control protocol (PCCP). Unlike existing work, PCCP innovatively measures congestion degree as the ratio of packet inter-arrival time along over packet service time. PCCP still introduced node priority index to reflect the importance of each sensor node. Based on the introduced congestion degree and node priority index, PCCP utilizes a cross-layer optimization and imposes a hop-by-hop approach to control congestion. We have demonstrated that PCCP achieves efficient congestion control and flexible weighted fairness for both single-path and multi-path routing, as a result this leads to higher energy efficiency and better QoS in terms of both packet loss rate and delay.

System and method for adjusting the window size of a tcp packet through network elements

Abstract: A system for adjusting the window size of a TCP packet on a packet network including a sending network element in communication with a receiving network element for transmitting and receiving data packets between the sending network element and the receiving network element on the packet network, wherein at least one of the sending network element and the receiving network element is configured to determine network performance information of the packet network; concatenate the network performance information into the data packets; and adjust the window size of the TCP packet based on the network performance information. A method for adjusting the window size of a TCP packet on a packet network is also included.

Minimising the effect of WiFi interference in 802.15.4 wireless sensor networks

Abstract: Interference from colocated networks operating over the same frequency range, becomes an increasingly severe problem as the number of networks overlapping geographically increases. Our experiments show that such interference is indeed a major problem, causing up to 58% packet loss to a multihop 802.15.4 sensor network competing for radio spectrum with a WiFi network. We present interference estimators that can be efficiently implemented on resource constrained motes using off-the-shelf radios and outline distributed algorithms that use these estimators to dynamically switch frequencies as interference is detected. Lastly, we evaluate the proposed algorithms in the context of a real-life application that downloads large amounts of data over multihop network paths. Our results show that the proposed approach successfully detects interference from competing WiFi channels and selects non-overlapping 802.15.4 channels. As a result, the proposed solution reduces end-to-end loss rate from 22% 58% to < 1%.

System and method for dynamically shaping network traffic

Abstract: A system for dynamically shaping data packet traffic on a packet network including at least one customer access node for communicating the data packets on the packet network; at least one customer premises equipment in communication with the at least one customer access node; at least one Internet gateway for communicating the data packets from an Internet, the at least one Internet gateway in communication with the at least one customer access node through the packet network; and at least one data packet rate shaper in communication with the at least one Internet gateway for shaping the rates of transmission of the data packets through the packet network based on network performance data transmitted by the at least one customer access node to the Internet gateway. A method for dynamically shaping data packet traffic on a packet network is also included.

Wireless Sensor/Actuator Network Design for Mobile Control Applications

Abstract: Wireless sensor/actuator networks (WSANs) are emerging as a new generationof sensor networks. Serving as the backbone of control applications, WSANs will enablean unprecedented degree of distributed and mobile control. However, the unreliability ofwireless communications and the real-time requirements of control applications raise greatchallenges for WSAN design. With emphasis on the reliability issue, this paper presents anapplication-level design methodology for WSANs in mobile control applications. Thesolution is generic in that it is independent of the underlying platforms, environment,control system models, and controller design. To capture the link quality characteristics interms of packet loss rate, experiments are conducted on a real WSAN system. From theexperimental observations, a simple yet efficient method is proposed to deal withunpredictable packet loss on actuator nodes. Trace-based simulations give promisingresults, which demonstrate the effectiveness of the proposed approach.

Preventing Cooperative Black Hole Attacks in Mobile Ad Hoc Networks: Simulation Implementation and Evaluation

Abstract: A black hole attack is a severe attack that can be easily employed against routing in mobile ad hoc networks. A black hole is a malicious node that falsely replies for any route requests without having active route to specified destination and drops all the receiving packets. If these malicious nodes work together as a group then the damage will be very serious. This type of attack is called cooperative black hole attack. In S. Ramaswamy et al. (2003), we proposed a solution to identifying and preventing the cooperative black hole attack. Our solution discovers the secure route between source and destination by identifying and isolating cooperative black hole nodes. In this paper, via simulation, we evaluate the proposed solution and compare it with other existing solutions in terms of throughput, packet loss percentage, average end-to-end delay and route request overhead. The experiments show that (1) the AODV greatly suffers from cooperative black holes in terms of throughput and packet losses, and (2) our solution proposed in S. Ramaswamy et al. (2003) presents good performance in terms of better throughput rate and minimum packet loss percentage over other solutions, and (3) our solution can accurately prevent the cooperative black hole attacks. The example findings are: (1) the proposed scheme presents 5 - 8% more communication overhead of route request; and (2) The secure route discovery delay slightly increases the packet loss percentage.

Dynamic Ethernet Link Shutdown for Energy Conservation on Ethernet Links

Abstract: Recent studies of network traffic utilization on campus networks have shown that data networks remain heavily under-utilized. Yet currently there is little attempt to save energy on network interfaces by using the low power modes available in Ethernet transceivers during periods of inactivity or low utilization. In this paper we design and evaluate a dynamic ethernet link shutdown (DELS) algorithm that utilizes current technology leading to significant benefits in energy savings with little noticeable impact on packet loss or delay. The algorithm uses buffer occupancy, the behavior of previous packet arrival times and a configurable maximum bounded delay to make sleeping decisions. The scheme was evaluated using simulations with inputs generated using a synthetic traffic generator for smooth and bursty traffic. The results show that the percentage of total time that a link can be shut down can be anywhere from 80% to 60% for traffic loads up to 5%.

System and method for enabling reciprocal billing for different types of communications over a packet network

Abstract: A system and method for determining inter-carrier network usage may be used. The method may include determining network usage of a first packet network managed by a first communications carrier by subscribers of a second communications carrier that manages a second packet network. The network usage may distinguish communications of data packets including real-time content and non-real-time content. Network usage of the second packet network by subscribers of the first communications subscriber may be determined. A network usage differential between the determined usages of the first and second packet networks may be determined, where the network usage information may distinguish communications of data packets including real-time and non-real-time content.

Radio transmission system and packet transmission terminal

Abstract: PROBLEM TO BE SOLVED: To prevent loss of data packets by rationalizing the transmission amount of the data packets. SOLUTION: A radio transmission system includes: a data packet transmission part 11 which transmits data packets to a packet reception terminal 2 by using a satellite line; an own station data packet reception part 12 which receives data packets transmitted from the data packet transmission part 11 and turned by a satellite; and a line band calculation part 13 which calculates an available band of a radio line from the reception quality of data packets received by the own station data packet reception part 12. A data transmission amount control part 18 controls the transmission amount of data packets transmitted from the data packet transmission part 11, in accordance with the available band calculated by the line band calculation part 13. COPYRIGHT: (C)2009,JPO&INPIT

Resource Allocation and Quality of Service Evaluation for Wireless Communication Systems Using Fluid Models

Abstract: Wireless systems offer a unique mixture of connectivity, flexibility, and freedom. It is therefore not surprising that wireless technology is being embraced with increasing vigor. For real-time applications, user satisfaction is closely linked to quantities such as queue length, packet loss probability, and delay. System performance is therefore related to, not only Shannon capacity, but also quality of service (QoS) requirements. This work studies the problem of resource allocation in the context of stringent QoS constraints. The joint impact of spectral bandwidth, power, and code rate is considered. Analytical expressions for the probability of buffer overflow, its associated exponential decay rate, and the effective capacity are obtained. Fundamental performance limits for Markov wireless channel models are identified. It is found that, even with an unlimited power and spectral bandwidth budget, only a finite arrival rate can be supported for a QoS constraint defined in terms of exponential decay rate

System and method for monitoring and optimizing network performance with user datagram protocol network performance information packets

Abstract: A method for monitoring and optimizing performance of a packet network utilizing user datagram protocol including determining network performance information between a sending user datagram protocol network element and a receiving user datagram protocol network element; concatenating the network performance information into data packets; transmitting the data packets to at least one non-user datagram protocol network device having transport layer capabilities; and controlling bandwidth of the at least one non-user datagram protocol network device to optimize the network utilizing the user datagram protocol based on the network performance information in the data packets. A system for monitoring and optimizing performance of a packet network utilizing user datagram protocol is also included.

Packet Loss Characterization in WiFi-Based Long Distance Networks

Abstract: Despite the increasing number of WiFi-based Long Distance (WiLD) network deployments, there is a lack of understanding of how WiLD networks perform in practice. In this paper, we perform a systematic study to investigate the commonly cited sources of packet loss induced by the wireless channel and by the 802.11 MAC protocol. The channel induced losses that we study are external WiFi, non-WiFi and multipath interference. The protocol induced losses that we study are protocol timeouts and the breakdown of CSMA over WiLD links. Our results are based on measurements performed on two real-world WiLD deployments and a wireless channel emulator. The two deployments allow us to compare measurements across rural and urban settings. The channel emulator allows us to study each source of packet loss in isolation in a controlled environment. Based on our experiments we observe that the presence of external WiFi interference leads to significant amount of packet loss in WiLD links. In addition to identifying the sources of packet loss, we analyze the loss variability across time. We also explore the solution space and propose a range of MAC and network layer adaptation algorithms to mitigate the channel and protocol induced losses. The key lessons from this study were also used in the design of a TDMA based MAC protocol for high performance long distance multihop wireless networks [12].

Speeding up parallel GROMACS on high-latency networks

Abstract: We investigate the parallel scaling of the GROMACS molecular dynamics code on Ethernet Beowulf clusters and what prerequisites are necessary for decent scaling even on such clusters with only limited bandwidth and high latency. GROMACS 3.3 scales well on supercomputers like the IBM p690 (Regatta) and on Linux clusters with a special interconnect like Myrinet or Infiniband. Because of the high single-node performance of GROMACS, however, on the widely used Ethernet switched clusters, the scaling typically breaks down when more than two computer nodes are involved, limiting the absolute speedup that can be gained to about 3 relative to a single-CPU run. With the LAM MPI implementation, the main scaling bottleneck is here identified to be the all-to-all communication which is required every time step. During such an all-to-all communication step, a huge amount of messages floods the network, and as a result many TCP packets are lost. We show that Ethernet flow control prevents network congestion and leads to substantial scaling improvements. For 16 CPUs, e.g., a speedup of 11 has been achieved. However, for more nodes this mechanism also fails. Having optimized an all-to-all routine, which sends the data in an ordered fashion, we show that it is possible to completely prevent packet loss for any number of multi-CPU nodes. Thus, the GROMACS scaling dramatically improves, even for switches that lack flow control. In addition, for the common HP ProCurve 2848 switch we find that for optimum all-to-all performance it is essential how the nodes are connected to the switch's ports. This is also demonstrated for the example of the Car-Parinello MD code.

Avoiding transient loops during the convergence of link-state routing protocols

Abstract: When using link-state protocols such as OSPF or IS-IS, forwarding loops can occur transiently when the routers adapt their forwarding tables as a response to a topological change. In this paper, we present a mechanism that lets the network converge to its optimal forwarding state without risking any transient loops and the related packet loss. The mechanism is based on an ordering of the updates of the forwarding tables of the routers. Our solution can be used in the case of a planned change in the state of a set of links and in the case of unpredictable changes when combined with a local protection scheme. The supported topology changes are link transitions from up to down, down to up, and updates of link metrics. Finally, we show by simulations that sub-second loop-free convergence is possible on a large Tier-1 ISP network.

Data structures and state tracking for network protocol processing

Abstract: Described are data structures, and methodology for forming same, for network protocol processing. A method for creating data structures for firewalling and network address translating is described. A method for creating data structures for physical layer addressing is described. A method for security protocol support using a data structure is described. A method for creating at least one data structure sized responsive to whether a firewall is activated is described. A data structure for routing packets is described. A method of forming hashing table chains is described. Additionally, method and apparatus for tracking packet states is described. More particularly, Transmission Control Protocol (“TCP”) tracking of states for packets is described. In an embodiment, a division between software states and hardware states is made as a packet is processed by both software and hardware. Additionally, method and apparatus for network protocol processing are described. For example, a packet for network address translation having a media access control header is obtained, from which information, including the media access control header, is obtained. The information is parsed into one or more data structures. It is determined whether a network processing unit is in a first round processing mode, or a second round pass-through mode.

Traffic Analysis and Modeling for World of Warcraft

Abstract: The popularity of MMOGs (massively multiplayer online games) has grown fast. This new type of online games uses a different type of protocol and has other limitations to delay and packet loss than the classical well established games like FPSs (first person shooters). This paper focuses on the traffic patterns generated by a MMOG named WoW (World of Warcraft). We analyzed IP layer information like packet size and rate from network traces and user level information like session durations. Finally we present a simple synthetic traffic generator for WoW traffic clients.

Performance analysis of ad-hoc networks under black hole attacks

Abstract: A wireless ad-hoc network is a temporary network set up by wireless nodes usually moving randomly and communicating without a network infrastructure. Due to security vulnerabilities of the routing protocols, however, wireless ad-hoc networks may be unprotected against attacks by the malicious nodes. In this study the effects of black hole attacks on the network performance was investigated. Black hole attacks were simulated in Network Simulator 2 (ns-2) and measured the packet loss in the network with and without a black hole. A simple solution was also proposed against black hole attacks. This solution improved the network performance in the presence of a black hole by about 19%.

Congestion-Aware Routing Protocol for Mobile Ad Hoc Networks

Abstract: Congestion in mobile ad hoc networks leads to transmission delays and packet loss, and causes wastage of time and energy on recovery. Routing protocols which are adaptive to the congestion status of a mobile ad hoc network can greatly improve the network performance. In this paper, we propose a congestion-aware routing protocol for mobile ad hoc networks which uses a metric incorporating data-rate, MAC overhead, and buffer delay to combat congestion. This metric is used, together with the avoidance of mismatched link data-rate routes, to make mobile ad hoc networks robust and adaptive to congestion.

Optimization of PDP context usage

Abstract: In a mechanism for controlling a communication connection with policy control, after the communication connection with policy control is established in a communication network between a user equipment and service providing network element via a network control element on the basis of an initial packet data protocol context, a modification of the initial packet data protocol context for the communication connection is requested or initiated at the network control element. When the modification is authorized, relevant resources for a modified packet data protocol context usable for signalling traffic and transmission of media stream data are set up.

System and method for controlling network bandwidth with a connection admission control engine

Abstract: A system and method for controlling network bandwidth. Network performance information that includes information regarding real-time data packets using performance information packet data packets is gathered. The network bandwidth is throttled for each of a number of customers in a communications network using one or more connection admission control (CAC) engines based on the network performance information and quality of service guarantees.

Opportunistic Network Coding for Wireless Networks

Abstract: Network coding is an emerging and powerful solution that can significantly improve the throughput and power efficiency of wireless networks by allowing mixing of various traffic flows via algebraic operations. With network coding, however, a packet has to wait to be network-coded with others given the stochastic nature of the packet arrival process of the various flows. This may result in large delay and packet-loss rate. To overcome this limitation, a novel network coding approach, which we shall refer to as opportunistic network coding (ONQ, is presented in this paper. In this proposed approach, whether a packet is transmitted with or without network coding is determined by the buffer's queue state at a given node. We shall derive ONC's performance in terms of delay, packet-loss, and power consumption by formulating a Markov Chain and a Hidden Markov Model for the delay and power analysis. More importantly, we will develop an optimal ONC strategy with minimal average delay and zero packet-loss rate. In particular, we will show that there exists a fundamental tradeoff between average delay and power, which characterizes the performance limit of ONC.

System and method for using distributed network performance information tables to manage network communications

Abstract: A system, method and network communications device including a processing unit configured to communicate data packets with one or more network communications devices. The data packets include network performance information generated by the one or more network communications devices in response to receiving a portion of the data packets. The network communications device further includes a memory in communication with the processing unit. The memory is configured to store a table containing network performance information associated with the node segments through which the data packets are communicated with the one or more network communications devices. The processing unit is further configured to process the data packets to store the network performance information in the table. The network performance information is utilized to alter future communications of the data packets through the node segments.

System and method for monitoring and optimizing network performance with vector performance tables and engines

Abstract: A system for monitoring and optimizing performance on a packet network with vector performance tables including a network element including an input/output (I/O) unit configured to communicate data packets with at least one other network element on the packet network the data packets including network performance information; a processing unit configured to receive the data packets from the at least one other network element; and a memory in communication with the processing unit and configured to store a vector performance table including a compilation of the network performance information contained in the data packets, the processor configured to process the data packets to store the network performance information in the vector performance table. A method for monitoring and optimizing performance on a packet network with vector performance tables is also included.

Practical Packet Analysis: Using Wireshark to Solve Real-World Network Problems

Abstract: It's easy to capture packets with Wireshark, the world's most popular network sniffer, whether off the wire or from the air. But how do you use those packets to understand what's happening on your network?With an expanded discussion of network protocols and 45 completely new scenarios, this extensively revised second edition of the best-selling Practical Packet Analysis will teach you how to make sense of your PCAP data. You'll find new sections on troubleshooting slow networks and packet analysis for security to help you better understand how modern exploits and malware behave at the packet level. Add to this a thorough introduction to the TCP/IP network stack and you're on your way to packet analysis proficiency.Learn how to: Use packet analysis to identify and resolve common network problems like loss of connectivity, DNS issues, sluggish speeds, and malware infections Build customized capture and display filters Monitor your network in real-time and tap live network communications Graph traffic patterns to visualize the data flowing across your network Use advanced Wireshark features to understand confusing captures Build statistics and reports to help you better explain technical network information to non-techies Practical Packet Analysis is a must for any network technician, administrator, or engineer. Stop guessing and start troubleshooting the problems on your network.