Abstract: Consider a setting in which a group of nodes, situated in a large underlying network, wishes to reserve bandwidth on which to support communication. Virtual private networks (VPNs) are services that support such a construct; rather than building a new physical network on the group of nodes that must be connected, bandwidth in the underlying network is reserved for communication within the group, forming a virtual “sub-network.”Provisioning a virtual private network over a set off terminals gives rise to the following general network design problem. We have bounds on the cumulative amount of traffic each terminal can send and receive; we must choose a path for each pair of terminals, and a bandwidth allocation for each edge of the network, so that any traffic matrix consistent with the given upper bounds can be feasibly routed. Thus, we are seeking to design a network that can support a continuum of possible traffic scenarios.We provide optimal and approximate algorithms for several variants of this problem, depending on whether the traffic matrix is required to be symmetric, and on whether the designed network is required to be a tree (a natural constraint in a number of basic applications). We also establish a relation between this collection of network design problems and a variant of the facility location problem introduced by Karger and Minkoff; we extend their results by providing a stronger approximation algorithm for this latter problem.

Abstract: There are two general structures to design a control system through a network. The first structure is to have several subsystems, in which each of the subsystem contains a set of sensors, a set of actuators, and a controller by itself. These system components are attached to the same control plant. In this case, a subsystem controller receives a set point from the central controller. Another structure is to connect a set of sensors and a set of actuators to a network directly. Sensors and actuators in this case are attached to a plant, while a controller is separated from the plant via a network connection to perform a closed-loop control over the network. A challenging problem in control of networked-based system is network delay effects. The time to read a sensor measurement and to send a control signal to an actuator through the network depends on network characteristics such as their topologies, routing schemes, etc. Therefore, the overall performance of a network-based control system can be significantly affected by network delays. The severity of the delay problem is aggravated when data loss occurs during a transmission. Moreover, the delays do not only degrade the performance of a network-based control system, but also can destabilize the system. This tutorial presents fundamental details of network-based control and recent network-based control techniques for handling the network delays. The techniques are based on various concepts such as state augmentation, queuing and probability theory, nonlinear control and perturbation theory, and scheduling. A general structure of a network-based control system, delay types, and delay behaviors are also described in this tutorial. In addition, advantages and disadvantages of these techniques are discussed.

Abstract: Traditionally, research in secure group key agreement focuses on minimizing the computational overhead for cryptographic operations, and minimizing the communication overhead and the number of protocol rounds is of secondary concern. The dramatic increased in computation power that we witnessed during the past years exposed network delay in WANs as the primary culprit for a negative performance impact on key agreement protocols. The majority of previously proposed protocols optimize the cryptographic overhead of the protocol. However, high WAN delay negatively impacts their efficiency. The goal of this work is to construct a new protocol that trades off computation with communication efficiency. We resurrect a key agreement protocol previously proposed by Steer et al. We extend it to handle dynamic groups and network failures such as network partitions and merges. The resulting protocol suite is provably secure against passive adversaries and provides key independence, i.e. a passive adversary who knows any proper subset of group keys cannot discover any other group keys not included in the subset. Furthermore, the protocol is simple, fault-tolerant, and well suited for high-delay wide area network.

Abstract: A method and system for profiling network flows at a measurement point within a computer network is provided. The method includes measuring network flows having invariant features at a measurement point located within routing infrastructure of the computer network to obtain flow statistics. The method also includes aggregating the flow statistics to obtain a traffic profile of the network flows at the measurement point. The method and system utilize the natural hierarchy in the Internet addressing scheme to provide a means for making tractable measurements of network traffic in high-speed networks. Moreover, the method and system adapt dynamically to the changing underlying traffic characteristics to maintain a maximum memory footprint for the profiles. The method and system adapt by adjusting the level of aggregation of the traffic endpoints along a scale from Interface to fully specified network address.

Abstract: A network processing endpoint system for responding to network requests via a network is provided. A network processor is programmed to receive network requests and to provide load balancing of the network requests or workloads. The network processor distributes network requests to a set of processing units, which are programmed to respond to the requests. An interconnection medium, which may be a system bus, a switch fabric, or shared memory, directly connects the network processor to the processing units, such that the paths and latencies of the connections are deterministic. Hardware load balancing of the processing units may also be accomplished through the assignment or re-assignment of the processing units to specific tasks to be performed.

Abstract: A system for transmitting and synchronizing real-time multimedia content includes a multimedia server for generating a multimedia packet; a packet-based communication network connected to the multimedia server for receiving multimedia packets therefrom; the network having multiple routers therein to route the multimedia packets to plural destinations; a mechanism for inserting total delay information (TDI) into the multimedia packets, wherein the TDI includes total end-to-end delay (TED) and cumulative network delay (CND); and plural multimedia receivers for receiving the multimedia packets having TDI therein, wherein each multimedia receiver includes a buffer, a sequencing mechanism, and a playing mechanism for playing retrieved, sequenced multimedia packets at time TED after the multimedia packet has been transmitted by the multimedia server. A method of transmitting and synchronizing real-time multimedia content includes loading multimedia audio/visual into plural multimedia packets; inserting total delay information (TDI) into at least one of the multimedia packets, wherein TDI includes total end-to-end delay (TED) and cumulative network delay (CND); transmitting the multimedia packets to plural multimedia receivers over a packet-based network in a play sequence; and playing the multimedia packets at each receiver at time TED.

Abstract: A congestion management technique achieves an end-to-end data flow rate that is supported by a lossless communications network. The end-to-end rate extends from a source end node to destination end node of the network and is preferably at or slightly below a bottleneck rate of the network. The destination end node determines, on its own and without any help from network elements, a supportable rate of activity in the network and provides feedback to the source end node. By achieving such a rate, data transmitted by the source end node can flow through the network without loss of packets and without the use of substantial buffering.

Abstract: A new receiver-based playout scheduling scheme is proposed, which estimates the network delay from past statistics and adaptively adjusts the playout time of the voice packets. In contrast to previous work, the adjustment is not only performed in between talkspurts, but also within the talkspurts in a highly dynamic way. Proper reconstruction of continuous output speech is achieved by scaling individual voice packets using a time-scale modification technique which modifies the rate of playout while preserving voice pitch. Subjective listening tests show that this operation does not impair the audio quality. Simulation results based on Internet measurement indicate that buffering delay and loss rate can be significantly reduced by adaptive scheduling.

Abstract: In this paper we study the performance trade-offs between conventional cellular and multi-hop ad-hoc wireless networks. We compare through simulations the performance of the two network models in terms of raw network capacity, end-to-end throughput, end-to-end delay, power consumption, per-node fairness (for throughput, delay, and power), and impact of mobility on the network performance. The simulation results show that while adhoc networks perform better in terms of throughput, delay, and power, they suffer from unfairness and poor network performance in the event of mobility.We discuss the trade-offs involved in the performance of the two network models, identify the specific reasons behind them, and argue that the trade-offs preclude the adoption of either network model as a clear solution for future wireless communication systems. Finally, we present a simple hybrid wireless network model that has the combined advantages of cellular and ad-hoc wireless networks but does not suffer from the disadvantages of either.

Abstract: Delay is one of the most common problems in the construction industry. This paper presents a method for computing activity delays and assessing their contributions to project delay. The method consists of a set of equations, which can be easily coded into a computer program that allows speedy access to project delay information and activity contributions. The proposed method contrasts the as-planned and as-built schedules. It is not based on critical path analyses; therefore, it does not require the calculation or updating of the critical path, and it is even not necessary to update the as-planned schedule, as required by the traditional delay analysis methods. The results calculated from the proposed method include various variations of activity schedules and their contributions (in days) to the overall project delay. They provide an objective baseline for determining responsibilities of delays. The method can be integrated into any delay analysis system to further improve and automate the construction delay analysis process. Practical examples are used to illustrate the computation mechanism.

Abstract: Network elements at endpoints of a data connection are identified. A network path is generated between the network elements at the endpoints. The network path is validated by determining whether the network path provides at least one service requirement. The service requirement may be a minimum bandwidth requirement, a maximum bandwidth requirement, a maximum delay requirement, a maximum jitter requirement, a reliability requirement, a requirement that the network path includes network elements capable of acting as security gateways that bracket untrusted sections of the network path, a reachability requirement, or a data collection capability requirement. Network elements along a validated network path are configured to implement the service requirement. In one embodiment, the configuration performed on the network elements is recorded.

Abstract: In an interconnected power system, the network security and power transfer capability analyses require a complete network base case solution. With the advent of communications among operations control center computers, real-time telemetered data can be exchanged for complete network modeling. Measurement time skew is a consideration when combining large area data received via a data communication network. In order to accommodate the effects of randomly varying arrival of measurement data, this paper presents an implementation of a stochastic extended Kalman filter (EKF) algorithm, which provides optimal estimates of interconnected network states for systems in which some or all measurements are delayed. The method relies on the delay statistics of exchanged data arrival at the control center and the delay is assumed to have binary statistics, i.e., either the measurements arrive in time or they are delayed by one time sample. Performance of the proposed method is compared with that of the standard weighted least square (WLS) technique.

Abstract: In this paper, we explore the use of end-to-end unicast traffic measurements to estimate the delay characteristics of internal network links Experiments consist of back-to-back packets sent from a sender to pairs of receivers Building on recent work [11,5,4], we develop efficient techniques for estimating the link delay distribution Moreover, we also provide a method to directly estimate the link delay variance, which can be extended to the estimation of higher order cumulants Accuracy of the proposed techniques depends on strong correlation between the delay seen by the two packets along the shared path We verify the degree of correlation in packet pairs through network measurements We also use simulation to explore the performance of the estimator in practice and observe good accuracy of the inference techniques

Abstract: A communication network is dynamically optimized using network operation metrics, such as may be acquired from a network controller such as a mobile switching center, to achieve network performance goals. Operational parameter adjustments, associated with a particular network resource and corresponding network resources, are preferably determined as a function of the network operation metrics. Implementation of the parameter adjustments are modeled to determine if further or different operational parameter adjustments should be determined. Preferably, actual implementation of the parameter adjustments is effected in part through providing the adjusted parameters to the network controller. Additionally or alternatively, the adjusted parameters may be provided directly to one or more network resources for implementation.

Abstract: A method and apparatus for servicing transmit traffic in a node of a network where the network includes a plurality of nodes connected by first and second rings formed by two or more transmission media. The method includes receiving transit delay data associated with a plurality of downstream nodes, receiving a packet for routing to a destination node in the network and routing the packet to one of the first and second rings not only based on a shortest path to the destination node but also on a transmit latency for both the first and second rings in view of the received transit delay data.

Abstract: More and more multicast communications are becoming real-time. In real-time communications, messages must be transmitted to their destination nodes within a certain amount of time; otherwise the messages will be rendered futile. To support real-time multicast communications, computer networks have to guarantee an upper bound on the end-to-end delay from the source node to each of the destination nodes. This is known as the multicast end-to-end delay problem. On the other hand, if the same message fails to arrive at each destination node at the same time, there will probably arise inconsistency or unfairness problem among users. This is related to the multicast delay variation problem. Our research subject is concerned with the minimization of multicast delay variation under the multicast end-to-end delay constraint. The problem has been proved to be NP-complete and a heuristic algorithm for it called DVMA (delay variation multicast algorithm) has been proposed. In this paper we find that in spite of DVMA's smart performance in terms of multicast delay variations, its time complexity is as high as O(klmn/sup 4/). It is strongly believed that such a high time complexity does not fit in a modern high-speed computer network environment. Therefore, we present an alternative heuristic algorithm with a much lower time complexity O(mn/sup 2/) and with a satisfactory performance. Computer simulations also testify that our algorithm is both fast and efficient.

Abstract: Methods, apparatuses and systems allowing for deployment of volume-based network policies across a computer network. In one embodiment, the present invention monitors network utilization of a plurality of users and detects the occurrence of network utilization milestones or other events for individual users, such as exceeding a data transfer allotment or threshold. To enforce the allotment or threshold, the present invention is operative to deny, degrade, or otherwise affect a characteristic associated with network access provided to such users.

Abstract: Voice over IP is a hot topic for the networking technologies. Delay and delay jitter are the important measures of QoS particularly for the voice traffic in the network environment with bursty background traffic. This paper studies the performance behavior of delay and delay jitter at the IP packet level by using the transient queuing solution. The analysis focuses on the voice over IP traffic going through a IP router with the bursty background traffic over network. We study the individual effects of various traffic parameters on the jitter behavior of packet voice stream multiplexing background traffic with different bursty characteristics in the IP router. The numerical results for the investigation of the effects of delay and delay jitter to a speech sample are presented.

Abstract: The viability of storage outsourcing is critically dependent on the access performance of remote storage. We study this issue by measuring the behavior of a broad variety of I/O-intensive benchmarks as they access remote storage over an IP network. We measure the effect of network latencies that correspond to distances ranging from a local neighborhood to halfway across a continent. We then measure the effect of latency-hiding mechanisms. Our results indicate that, in many cases, the adverse effects of network delay can be rendered inconsequential by clever file system and operating system techniques.

Abstract: A scalable networking protocol that allows multiple nodes to communicate via a multi-channel network medium is described. The networking protocol allows any node on the network to assign itself as the active network server. The active network server polls client nodes based on a lineup card. The lineup card includes a high priority queue for low-latency devices, and a low priority queue for devices that can tolerate higher latencies. Network information is sent on the channels as fragments. The protocol provides bad-channel detection and retransmission of fragments in a fragment-by-fragment basis. Support for streaming data or asynchronous data is provided by allocating time slots on the network and allowing two intelligent nodes to talk directly to each other during count-limited token sessions, as arbitrated by the active network server. The network node serving as the active network server can be changed on a dynamic basis, and is typically determined by the first node initiating a transmit request on a sleeping network. Client nodes are addressed by dynamic-polling using an address isolation scheme.

Abstract: Inference of network internal link characteristics has become an increasingly important issue for operating and evaluating large telecommunication networks. Since it is usually impractical to directly monitor each link along a specific path, end-to-end probes are sometimes used to collect link characteristic information at edge nodes of the network. This paper deals with unicast probing methods for estimation of link delay characteristics. Unicast traffic is easy to generate and is supported by almost every network currently in operation. Under the assumptions that link delays are spatially and temporally independent, we propose a bias corrected estimator for the internal link delay cumulant generating function (CGF) based on unicast probe end-to-end delay measurements. Through simulation we show that the proposed estimator attains a level of mean squared error comparable to link delay CGF estimates obtained from directly measured link delay statistics. We can use these CGF estimates to estimate delay mean, variance and level exceedance probabilities for each link.

Abstract: As process technology goes into deep submicron range, interconnect delay becomes dominant among overall system delay, occupying most of the system clock cycle time. Interconnect delay is now a crucial factor that needs to be considered even during high-level synthesis. In this paper, we propose a concurrent scheduling and binding algorithm that takes interconnect delay into account. We first define our distributed target architecture, which minimizes the effect of interconnect delay on clock cycle time. We no longer assume that interconnect delay between functional units is a part of one clock cycle. Interconnect delay can span over multiple clock cycles. We incorporate the concept of multi-cycle interconnect delay into scheduling and binding process, to reduce the critical path length and therefore the system latency. We show that by introducing interconnect delay, we can obtain latency improvement of up to 54 % and of 37% on the average.

Abstract: We study the problem of determining the geographic location of an Internet host knowing only its IP address. We have developed three distinct techniques, GeoTrack, GeoPing, and GeoCluster, to address this problem. These techniques exploit information derived from the DNS, network delay measurements, and inter-domain routing. We have evaluated our techniques using extensive and varied datasets.

Abstract: A control system is disclosed for controlling data flow over a data-packet-network according to specific destinations. The system has a network monitoring system for monitoring network performance parameters; a network access system for accessing specific nodes in the network; and a control software executable on the network access system for assigning and changing cost parameters at selected nodes in the network. A network administrator uses the network access system and control software to assign and implement cost values at the selected nodes, the values associated individually with a specific destination or destinations, the values establishing forwarding costs to be incurred at the selected nodes, and link costs to be incurred per data link between the nodes such that manipulation of such cost value assignments enables load balancing of data traveling through the network. In one embodiment the data-packet-network is internal to a router and nodes comprise internal router cards.

Abstract: When a control system is implemented in a distributed fashion, with multiple processors communicating over a network, both the communication delays associated with the network and the computation delays associated with the processing time can degrade the system's performance. In this case, the performance of the system may depend not only on the performance of the individual components but also on their interaction and cooperation. The approach taken in this paper assumes that the control has been designed without taking into account the network architecture. A theoretical framework is presented which allows the effect of time delays on the mechanical performance of the system to be precisely modelled, and these models are used to determine the optimal network architecture for the given control system. A design example of a two-axis contouring system is presented.

Abstract: A novel method and apparatus for transmitting voice traffic and data traffic over a circuit-switched network and a packet-switched network are presented. A new service option is introduced that allows a circuit-switched network to strip off IP/UDP/RTP header information from an internet protocol packet that may or may not be carrying multimedia payloads. Selectively eliminating the reliability measures in the RLP layer allows the circuit-switched network to reduce the delay associated with data traffic, and thus satisfy the more stringent delay requirements of voice traffic.

Abstract: A system and method for transparently transmitting aural signals across a wide area network (WAN). The system of present invention is connected to one or more of a private branch exchange, a key telephone system, a telephone, a facsimile machine, and a modem, for example. In the case of voice transmission, a user places a telephone call using the same procedure that is used when placing a telephone call over a conventional public switched network. The aural signals are translated into a format that is compatible with the local area network (LAN) and the translated signals are transmitted to a router or a switch that connects the LAN to the WAN. The data is transmitted across the WAN to a router or switch coupled to a second LAN. The data is then sent to a destination central site unit or PC which translates the signal into a format that is compatible with the telephone system connected thereto. The present invention provides a voice quality that approaches, equals, or exceeds the voice quality of conventional telephone switched networks. This high voice quality is achieved by utilizing a high quality voice digitization algorithm, by ensuring a low maximum network delay, by dynamically compensating for variations in network delay, and by using a forward error correction technique that can recreate lost or delayed signals in a manner that recreates the signal so the lost signal is typically not detectable by a user.

Abstract: A wireless network includes a plurality of proxy servers located at various locations to selectively transform data based upon network conditions, such as link congestion. A queueing model for the network can be used to determine optimal operating parameters for the network.