Abstract: The design problem of networked control systems (NCS) with constant and random network delay in the forward and feedback channels, respectively, is considered in this paper. A novel networked predictive control (NPC) scheme is proposed to overcome the effects of network delay and data dropout. Stability criteria of closed-loop NPC systems are presented. The necessary and sufficient conditions for the stability of closed-loop NCS with constant time delay are given. Furthermore, it is shown that a closed-loop NPC system with bounded random network delay is stable if its corresponding switched system is stable. Both simulation study and practical experiments show the effectiveness of the control scheme

Abstract: A system and methodologies are disclosed for determining the geographic location of an Internet host. A first method infers host location based on the DNS names of the host of interest or other nearby network nodes. A second method employs network delay measurements from geographically distributed locations to triangulate the coordinates of the host. A third method couples partial host-to-location mapping information obtained from one or more sources with BGP or other routing information in order to infer location of the host of interest.

Abstract: A system and method for diagnosing a problem on a packet network. Network performance information associated with data packet communications over a packet network may be collected. A network performance information parameter may be monitored and a determination that the network performance information parameter crosses a threshold value may be made. In response to determining that the network performance information parameter crossed the threshold value, diagnostics may be initiated to determine a cause of the network performance information parameter crossing the threshold value.

Abstract: In a wireless communication network having a plurality of devices operating at different data rates that contend for access to the network, a method is provided that assigns network access parameters to one or more of the devices so as to control throughput on the network. Examples of network access control parameters are the maximum data packet size and the contention window size. Generally, the network access control parameter for slower data rate users is configured so that they do not occupy the network a disproportionate amount of time compared to faster data rate users.

Abstract: Network tomography has been regarded as one of the most promising methodologies for performance evaluation and diagnosis of the massive and decentralized Internet It can be used to infer unobservable network behaviors from directly measurable metrics and it does not require cooperation between the network internal elements and the end users For instance, the Internet users may estimate the link level characteristics such as loss and delay from end-to-end measurements, whereas the network operators can evaluate the Internet path-level traffic intensity based on link-level traffic measurements In this paper, we present a novel estimation approach for the network tomography problem Unlike previous likelihood based methods, our approach is based on characteristic functions, ie the Fourier transform, of the distributions of observed measurements We focus on network delay tomography and develop a Fourier domain inference algorithm based on flexible mixture models of link delays Through extensive model simulation and simulation using real Internet trace, we are able to demonstrate that the new algorithm is computationally more efficient and yields more accurate estimates than previous methods, especially for a network with heterogeneous link delays In addition, we obtain some identifiability results that can be applied to general distribution models for link delays

Abstract: A system and method for collecting network performance information from network communications devices may include requesting, from a network communications device operating on a packet network, a counter value generated from counting a network performance information parameter. The request may cause the counter value to be reset prior to overflowing.

Abstract: Network delays and delay variations are two of the most important network performance metrics directly impacting real-time applications such as voice over IP and time-critical financial transactions. This importance is illustrated by past work on understanding the delay constancy of Internet paths and recent work on predicting network delays using virtual coordinate systems. Merely understanding currently observed delays is insufficient, as network performance can degrade not only due to traffic variability but also as a result of routing changes. Unfortunately this latter effect so far has been ignored in understanding and predicting delay related performance metrics of Internet paths. Our work is the first to address this short coming by systematically analyzing changes in network delays and jitter of a diverse and comprehensive set of Internet paths. Using empirical measurements, we illustrate that routing changes can result in roundtrip delay increase of converged paths by more than 1 second. Surprisingly, intradomain routing changes can also cause such large delay increase. Given these observations, we develop a framework to analyze in detail the impact of routing changes on network delays between end-hosts. Using topology information and properties associated with routing changes, we explain the causes for observed delay fluctuations and more importantly identify routing changes that lead to predictable effects on delay-related metrics. Using our framework, we study the predictability of delay and jitter changes in response to both passively observed interdomain and actively measured intradomain routing changes.

Abstract: A system for centrally controlling packet network communications may include an input/output (I/O) unit configured to communicate data packets over a packet network with multiple network communications devices, a processing unit in communication with the I/O unit and configured to communicate with the network communications devices via respective node segments, and a memory in communication with the processing unit and configured to store a table. The processing unit may be configured to receive and store network performance information of node segments generated by the network communications devices. The network performance information may be stored in the table in association with indicia representative of the node segments, respectively. The processing unit may further be configured to control network communications by the network communications devices over the node segments based on the network performance information stored in the table.

Abstract: A system and method for monitoring performance of an asynchronous network may include communicating a first network performance data packet including a first indicia over an asynchronous network from a first network node to a second network node. A second network performance data packet including a second indicia may be communicated from the first network node to the second network node. At least one communications data packet may be communicated from the first network node to the second network node between communicating the first and second network performance data packets. At least one performance manager counter at the second network node may be incremented in response to receiving each communications data packet between the first and second network performance data packets.

Abstract: Delay is one of the network performance parameters that are often measured using passive or active techniques along with packet loss, bandwidth, etc. If used appropriately, these parameters can indicate performance status of the network, and they can be used in fault and performance management, network provisioning, traffic engineering, and performance prediction. However, it is difficult to extract sufficient information from original measurement data to derive precise results. In this paper, we show that the PDF (probability distribution function) of delay data can indicate network load situation. We also show that Pareto distribution can model end-to-end delay appropriately in a statistical manner and demonstrate some statistical characteristics of end-to-end delay using Pareto distribution.

Abstract: A network endpoint system and related method and computer program product for use in a network to support enhanced end-to-end QoS in the network. The network endpoint system is adapted to receive network data of varying priority on behalf of a data consumer operating at the application layer of a network protocol stack implemented by the network endpoint system. The network endpoint system includes a network interface controller adapted to receive network frames containing the network data, plural network data handling channels each having an associated priority, and priority processing logic adapted to transfer the network data from the network interface controller to the plural data handling channels on a prioritized basis according to the network data priority. Also disclosed are a network interface controller and a network node to support enhanced end-to-end QoS in a network.

Abstract: Two of the major challenges in networked haptic telepresence and teleaction systems are the time delay associated with the data transmission over the network and the limited communication resources. Sophisticated control methods are available for the stabilization in the presence of time delay. The reduction of haptic network traffic, however, is only poorly treated in the known literature. Data reduction approaches for time delayed haptic telepresence are not available at all. This article presents a novel approach to reduce the network traffic in haptic telepresence systems with constant (unknown) time delay. With the proposed deadband control approach data are sent only if the signal to transmit changes more than a given threshold value. In order to guarantee stability with time delay and data reduction a well-known time delay approach, the scattering transformation, is extended. Experimental user studies show that an average network traffic reduction up to 96% is achieved without significantly impairing the perception of the remote environment compared to the standard approach with time delay.

Abstract: A method for evaluating access rules violations, the method includes: receiving, a model of a computer network; and determining security metrics associated with a violation of an access rule in response to: the model of the computer network, multiple network nodes of the computer network accessible according to at least one violated access rule or according to the network model, at least one vulnerability associated with the multiple network nodes, and damage associated with an exploitation of the at least one vulnerability.

Abstract: An ad-hoc network approach for addressing ad-hoc network address assignment, name resolution, and service discovery in ad-hoc networks. The size of the ad-hoc network may be limited to a selected number of ad-hoc network stations. A first portion of the ad-hoc network address assigned to stations joining the ad-hoc network may be fixed and a second portion of the ad-hoc network address may be selected dynamically, as each new station joins the ad-hoc network. A station may generate an information element that may be included in ad-hoc network messages. An exemplary information element may include a last byte of the ad-hoc network address associated with the transmitting station, a 4-byte timestamp field which indicates a number of milliseconds since the station claimed the network address, a user-friendly name to identify the station, a universally unique identifier (UUID) for each service offered by the transmitting station, and a network-address-in-use bitmap.

Abstract: A method for acquiring and disseminating network node characteristics to enable policy decisions including receiving a resolution request from one or more clients in a network environment. Information, for example, network address, is then acquired from one or more sources regarding a specific location in a network, for example, a network node. A list of the network addresses is then generated and ranked based on one or more parameters that merit making traffic handling decisions. The network addresses are then associated with a host name on at least one directory server and then propagated to the one or more clients.

Abstract: A technique dynamically responds to non-network events at a network device in a computer network. According to the novel technique, one or more sensors automatically detect (sense) one or more non-network events, and notifications of the non-network events are then transmitted over the network. One or more network devices (e.g., data centers, servers, routers, etc.) detect the notifications of the network events, and dynamically respond to the non-network events based on one or more associated policies. For example, one or more network-based policies may be defined that modify one or more network configuration parameters in response to the non-network events. Alternatively or in addition, one or more physical-based policies may be defined that instruct one or more network-attached physical control devices to modify one or more physical parameters.

Abstract: We study the scaling law governing the delay gains of network coding as compared to traditional transmission strategies in unreliable wireless networks. We distinguish between two types of traffic, namely elastic and inelastic, where the elasticity of a flow is based on the delay constraints associated with it. This novel formulation is useful in that it allows for the modeling of real-time traffic more accurately. Considering the limited availability of feedback in such systems, we focus on strategies with minimal acknowledgement requirements. Under both traffic types, we provide an extensive analysis of the gains of network coding as compared to traditional transmission strategies in a single-hop setting, and show that the gains are significant in general and can be considerably large in some cases. We further provide a method for realizing these gains in multi-hop networks with general topologies using the analysis of the single hop scenario.

Abstract: Logical channels in a network are automatically be configured by using measured network parameters. The measured network parameters are determined in cooperation with the network elements without interruption of active communication services. The network parameters include upstream or downstream modulation error ratio (MER), upstream or downstream signal to noise ratio (SNR), upstream or downstream microreflections, upstream transmit level, downstream receive power level, cable modem type (DOCSIS 1.0,1.1,2.0), functional capabilities (e.g., VoIP, 256QAM, etc), network element location with in a cable plant (e.g., node location or amplifier cascade depth), network element manufacturer, or type of services provided by the network element (including telephony versus data). An interactive display is provided to an operator which enables analysis of communication parameters, including modulation profiles and channel performance.

Abstract: The Mirrored Server (MS) architecture uses multiple mirrored servers across multiple locations to alleviate the bandwidth bottleneck in the Client/Server (C/S) architecture. Each mirror receives and multicasts player updates to the others, simulates the game, and disseminates the new game state to players. However, keeping the game state consistent between mirrors in the presence of network delay, and maintaining game responsiveness requires each server in MS to simulate the game multiple times for each game update, and additional times in the event of costly rollbacks. In this paper we propose the Enhanced Mirrored Server (EMS) architecture. Like in the Peer-to-Peer architecture, EMS allows peers to exchange updates directly, resulting in a higher tolerance to delay at the mirrors. We propose using bucket synchronization in the mirrors so that each server in EMS simulates the game only once for each update and does not require rollbacks. The server dissenates updates to clients only in the event of inconsistency, and thus its outgoing bandwidth is lower than in MS. Our EMS uses cryptographic techniques to provide security equivalent to C/S, and prevents the timestamp cheat possible in MS. Our analytical analysis and simulations show the advantages of EMS over MS.

Abstract: Many techniques have been proposed in the last few years to address performance degradations in end-to-end congestion control. Although these techniques require parameter tuning to operate in different congestion scenarios, they miss the challenging target of both minimizing network delay and keeping goodput close to the network capacity. In this paper we propose a new mechanism, called Active Window Management (AWM), which addresses these targets by stabilizing the queue length in the network gateways. AWM acts on the Advertised Window parameter in the TCP segment carrying the acknowledge, but it does not affect the TCP protocol. The proposed technique is implemented in the network access gateways, that is, in the gateways through which both the incoming and outgoing packets related to a given TCP connection are forced to go, whatever the routing strategy used in the network. We show that when the access gateways implementing AWM are the bottleneck in the networks, TCP performance is very close to that of a pseudo constant bit rate protocol providing no loss, while network utilization is close to one.

Abstract: A packet scheduler reduces or 'compresses' the packet transmission delay jitter or delay range where packets experience little or no scheduling delay before transmission. As a result, the number of packets that experience little or no delay is reduced. A preferred example way of compressing the packet transmission delay jitter is to reduce the transmission priority of low delay packets. Compressing the delay jitter is particularly desirable for services like VoIP that require low packet transmission delay jitter.

Abstract: Networks need to accommodate diverse applications with different quality-of-service (QoS) requirements. New ideas at the physical layer are being developed for this purpose, such as diversity embedded coding, which is a technique that combines high rates with high reliability. We address the problem of how to fully utilize different rate-reliability characteristics at the physical layer to support different types of traffic over a network and to jointly maximize their utilities. We set up a new framework based on utility maximization for networks with composite links, meaning that each link consists of sub-links that can attain different rate-reliability characteristics simultaneously. We incorporate delay, in addition to rate and reliability, into the utility functions. To accommodate different types of traffic, we propose distributed algorithms for the optimal rate-reliability-delay tradeoff based on capacity division and priority queueing. Numerical results show that compared with traditional codes, the new codes can provide higher network utilities for all traffic types simultaneously. The results also show that priority queueing achieves higher network utility than capacity division.

Abstract: Remote control over wireless multi-hop networks is considered. Time-varying delays for the transmission of sensor and control data over the wireless network are caused by a randomized multi-hop routing protocol. The characterstics of the routing protocol together with lower-layer network mechanisms give rise to a delay process with high variance and stepwise changing mean. A new predictive control scheme with a delay estimator is proposed in the paper. The estimator is based on a Kalman filter with a change detection algorithm. It is able to track the delay mean changes but efficiently attenuate the high frequency jitter. The control scheme is analyzed and its implementation detailed. Network data from an experimental setup are used to illustrate the efficiency of the approach.

Abstract: A methodology and network tool for evaluating one-way directional delays in a packet network is described. The invention provides for a discrimination of the directional components of the delay experienced by packets travelling between nodes in a network. This identification of the directional delay component assists in an understanding of network behaviour and can be represented on a graphical user interface. Such methodologies are achieved without requiring clock synchronisation between clocks at each of the nodes.

Abstract: We address the problem of allocating transmission rates to a set of network sessions with end-to-end bandwidth and delay requirements. We give a unified convex programming formulation that captures both average and probabilistic delay requirements. Moreover, we present a distributed algorithm and establish its convergence to the global optimum of the overall rate allocation problem. In our algorithm, session sources selfishly update their rates as to maximize their individual benefit (utility minus bandwidth cost), the network partitions end-to-end delay requirements into local per-link delays, and the links adjust their prices to coordinate the sources' and network's decisions, respectively. This algorithm relies on a network utility maximization (NUM) approach, and can be viewed as a generalization of TCP and active queue management (AQM) algorithms to handle end-to-end QoS. We extend our results to deterministic delay requirements when nodes employ Packet-level Generalized Processor Sharing (PGPS) schedulers.

Abstract: The invention proposes a method for handing over a session between a source network which provides a first connection type domain and a target network which provides the first connection type domain and a second connection type domain, comprising informing a network node (e.g., a user equipment (UE)), before performing a handover from the source network to the target network, a preferred transfer domain in the target network. The invention also proposes a corresponding network node and a network control element.

Abstract: Haptic tele-mentoring refers to an educational technique in which the mentor can teach the mentee, in a hand-by-hand manner over communication networks, through the coupling of two haptic devices Essentially, the realization of tele-mentoring relies on the efficient transmission of haptic information, such that either end of the network can sense and/or impart forces A few of obstacles in developing the tele-mentoring applications over the internet are network delay, jitter, and packet loss These impairments potentially affect the stability of the tele-mentoring system and degrade the feeling of guiding This paper analyzes the design and implementation constraints of the system, as well as the simulation and experimental results To compensate for the network latency, a novel approach based on the behaviors of the human arm trajectory is proposed to lower the overshoot so as to improve the overall system stability The experimental results show the effectiveness of the anti-overshoot algorithm

Abstract: The paper is concerned with the design and stability analysis of networked control systems with random network delay, which are described in a state-space form. It presents a new control scheme, which is termed networked predictive control. This scheme mainly consists of the control prediction generator and network delay compensator. The control prediction generator provides a set of future control predictions to make the closed-loop system achieve the desired control performance and the network delay compensator removes the effects of the network transmission delay. The stability criteria of the closed-loop networked predictive control systems are analytically derived for fixed. In case of random network delay, a switched system's method has been proposed, which solves the stochastic problem in a deterministic way.

Abstract: In this paper, a delay tolerant network environment is considered where the source is in full control of the two-hop spreading mechanism by setting key parameters such as the number of copies allowed to be spread in the network and the delay bound of the messages. The analysis allows for a differentiation between the source of the message and the intermediate nodes (in terms of e.g. transmission power or speed). Analytical expressions for the cumulative distribution function (cdf) of the delivery delay and the induced overhead are extracted, taking into account the fact that the source node may continue spreading copies after the message delivery. In addition, a fairly accurate approximate expression for the cdf of the delivery delay is also derived and validated through simulations.