Abstract: A method for estimating the network-layer topology of a telecommunications network is described. In particular, the illustrative embodiment of the present invention estimates the existence and connectivity of nodes in the topology based on the detection of network-wide end-to-end path intersections. This is based on the assumption that pairs of streams of packets that share a common node will interfere and that the interference can be detected in the received streams. In general, this interference is manifested as jitter. By transmitting streams on each pair of end-to-end paths in the network, and detecting interference (or a lack of interference) a matrix of path intersections for the network can be created. Using logic and supposition, the topology of the network can be estimated using the matrix of path intersections. Once the estimate of the topology is complete, the maintenance and operation of the network can proceed based on the topology.

Abstract: A network monitoring and analysis system is configured to include a root cause analysis function that permits the automatic determination of performance problem locations in a network of a communication system comprising a plurality of endpoint devices. Test communications are generated in the system in accordance with a selected pattern, which may be based on a flow matrix, and end-to-end path measurement data is collected utilizing the generated test communications. The end-to-end path measurement data is transformed to produce a plurality of performance indicators comprising a performance indicator for each of a plurality of non-end-to-end paths defined at least in part by the selected pattern.

Abstract: A technique is disclosed that attempts to improve the evaluation of a network path's signal quality, as well as the selection of a network path for transmission purposes, without some of the costs and disadvantages of doing so in the prior art. In accordance with the illustrative embodiment, a node with access to the packet network, such as a VoIP telephone endpoint, evaluates the quality of service that is associated with each of multiple network paths. The evaluation process is iterative, in which the number of candidate paths is successively reduced from one iteration of the technique to the next. The multiple paths that remain as candidates in any given iteration are evaluated concurrently and at an evaluation bit rate that i) is less than the full transmission rate of the real-time traffic (VoIP) packets to be sent and ii) varies as a function of the number of candidate paths remaining under consideration.

Abstract: A technique that seeks to direct and re-direct streams of packets through a packet network without adversely affecting the quality of service of existing streams is disclosed. In accordance with the illustrative embodiment of the present invention, streams of packets that are directed and re-directed through a packet network are initially put on probation. During the probation period, a quality-of-service measure for the stream is compared with a threshold whose value is initially high and decreases with time. This has the advantageous affect of noticing problems quickly so that they can be remediated quickly.

Abstract: A network monitoring and analysis system is configured to conduct performance analysis on a network using a plurality of endpoint devices. Locations of respective endpoint devices for use in the performance analysis of the network are determined utilizing an algorithm which characterizes the network as a graph having edges and vertices and associates endpoint devices with particular ones of the vertices in an iterative manner based on impact of said vertices on achievement of a specified coverage criterion. The coverage criterion may comprise a links-covered criterion which specifies a percentage of a total number of links of the network that are covered by test communications. As another example, the coverage criterion may comprise a links-estimable criterion which specifies a percentage of a total number of links of the network for which performance is estimable from collected end-to-end path measurement data.

Abstract: Techniques are disclosed for improved monitoring and analysis of VoIP communications, multimedia communications or other types of network traffic in a network-based communication system. In accordance with one aspect of the invention, an endpoint device of the system includes an integrated call synthesis capability. More particularly, the endpoint device is configurable into at least a first mode of operation in which the device responds to one or more commands from a testing server of the system directing the device to participate in a synthetic call or other test communication within the system, and a second mode of operation in which the device is utilizable by a system user to establish an actual communication. Other aspects of the invention relating to kernel timestamping and timestamp post-processing provide improved accuracy for measurements such as jitter, loss and delay.

Abstract: A method and apparatus are disclosed that seek to improve the quality of service that is experienced during the transmission of a stream of packets across one or more paths. In particular, a transmitting node encodes a source stream of data (e.g., audio, video, etc.) into one or more sub-streams, and distributes those sub-streams onto multiple network transmission paths. In accordance with the illustrative embodiment of the present invention, the transmitting node evaluates the quality of service of a first network path that fails to provide a quality-of-service guarantee. When the quality of service of the first network path becomes unsatisfactory, the coding of one or more sub-streams that are being transmitted on a second network path is adjusted. In other words, the coding on a second channel is adjusted in response to the changing conditions on a first channel.

Abstract: A technique is disclosed that evaluates a network path between (i) a first node in a first subnetwork of endpoint nodes, such as IP phones, and (ii) a second node in a second subnetwork. A “ricochet” node in the network path evaluates the path by probing one or both subnetworks, where the ricochet node acts as relay for traffic packets being transmitted between the two subnetworks. A given relay has only to probe a single, representative node within a subnetwork at any given time in order to obtain performance data that is representative of the subnetwork overall. By probing the representative node, the relay is able to acquire an assessment of network conditions that is valid for the path between the relay and any endpoint in the subnetwork. As a result, the disclosed technique reduces the probing overhead when many endpoint nodes on a given subnetwork are simultaneously active and experiencing adverse network conditions.

Abstract: A network monitoring and analysis system is configured to include a root cause analysis function that permits the automatic determination of performance problem locations in a network of a communication system comprising a plurality of endpoint devices. Test communications are generated in the system in accordance with a selected pattern, which may be based on a flow matrix, and end-to-end path measurement data is collected utilizing the generated test communications. The end-to-end path measurement data is transformed to produce a plurality of performance indicators comprising a performance indicator for each of a plurality of non-end-to-end paths defined at least in part by the selected pattern.

Abstract: Techniques are disclosed for improved monitoring and analysis of VoIP communications, multimedia communications or other types of network traffic in a network-based communication system. In accordance with one aspect of the invention, an endpoint device of the system includes an integrated call synthesis capability. More particularly, the endpoint device is configurable into at least a first mode of operation in which the device responds to one or more commands from a testing server of the system directing the device to participate in a synthetic call or other test communication within the system, and a second mode of operation in which the device is utilizable by a system user to establish an actual communication. Other aspects of the invention relating to kernel timestamping and timestamp post-processing provide improved accuracy for measurements such as jitter, loss and delay.

Abstract: A system discovers the topology of devices in a network, such as all of the layer-2 and layer-3 devices, including routers and switches. The devices are mapped, as well as the links that join them. The devices are polled using SNMP requests. Route tables are derived from each router to determine addresses of the devices. A spanning tree process is used to discover layer-2 devices. Connections between layers are then discovered. Where information is incomplete, an undiscovered router cloud is recognized.

Abstract: A system visualizes and generates reports from stored data, concerning various measured parameters related to a network carrying call traffic. The network is displayed in an easily recognized arrangement, with various parameters being indicated by different shapes and colors for each device on the network. The parameters are changed to indicate the status of the network at different times. More detailed information about a parameter, a device or a path between devices may be obtained simply using a mouse or keystrokes. A variety of different types of detailed displays allows the operator to troubleshoot problems in the network.

Abstract: A system for monitoring traffic on a network first discovers the network so as to map the various devices and links in the network. Statistics are then gathered from various points in the network relating to quality of service, and especially loads on the network devices. Synthetic calls are generated at selected points of the network while monitoring the network. This data is then stored and displayed in a manner that is easy for the operator to analyze, with more detailed displays being available through the use of a mouse or keystrokes.