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 multi-stage technique of establishing a plurality of secure strings of symbols is disclosed. In the first stage, the illustrative embodiment establishes a first-stage string of symbols with each other node. The first-stage strings are chosen from a first, small, key space, which means that they can be established more quickly than a highly secure key from a large key space. The advantage of the first-stage strings is that it enables the user to transmit secure messages more quickly than messages secured with highly secure strings. The disadvantage of the illustrative embodiment is that the first-stage strings are not as secure as strings from a larger key space. This disadvantage is mitigated, however, by the fact that the first-stage strings are only used for a short amount of time—until the second-stage strings are established in the second stage.

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 method is disclosed for conducting a search in which measurements of a time-varying property are made and updated during the search, and in which the measurements might be uncertain. In accordance with the illustrative embodiment, one or more search algorithm parameters (e.g., the maximum branching factor of a search tree, a depth cutoff for a search tree, a time cutoff, a threshold, etc.) are adjusted dynamically during the search based on at least one of: the degree of uncertainty of the measurements, the variability of measurements over time (e.g., standard deviation, etc.), and the fraction of members whose measurement is better than a threshold. In addition, the illustrative embodiment enables the search space to be pruned based on these criteria.

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 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 method is disclosed for adaptively and intelligently partitioning traffic among a plurality of communications channels, without injecting probe traffic into any of the channels. In accordance with the illustrative embodiment, a source node transmits traffic to a receiving node via K communications channels in accordance with partition coefficients ?1, . . . , ?K, and the source node receives information regarding the quality of service (QoS) provided by each of the communications channels. The source node adjusts the values of the partition coefficients ?1, . . . , ?K adaptively based on: the current channel QoS information, prior channel QoS information, the prior values of ?1, . . . , ?K, and a measure of channel independence for one or more pairs of communications channels.

Abstract: A multi-stage technique of establishing a plurality of secure strings of symbols is disclosed. In the first stage, the illustrative embodiment establishes a first-stage string of symbols with each other node. The first-stage strings are chosen from a first, small, key space, which means that they can be established more quickly than a highly secure key from a large key space. The advantage of the first-stage strings is that it enables the user to transmit secure messages more quickly than messages secured with highly secure strings. The disadvantage of the illustrative embodiment is that the first-stage strings are not as secure as strings from a larger key space. This disadvantage is mitigated, however, by the fact that the first-stage strings are only used for a short amount of time—until the second-stage strings are established in the second stage.

Abstract: Techniques for performing rapid fault detection and recovery in communication networks are disclosed. For example, in one aspect of the invention, a technique for detecting one or more conditions in a communication network comprises the following steps/operations. One or more keep-alive packets are transmitted from a source node in the communication network to a destination node in the communication network over two or more paths between the source node and the destination node, wherein the two or more paths are at least partially disjoint. Upon receipt of the one or more keep-alive packets at the destination node via the two or more paths, at least one quality measure is computed at the destination node for each of the two or more paths, the at least one quality measure being indicative of one or more conditions in the communication network.

Abstract: A method is disclosed for conducting a search in which measurements of a time-varying property are made and updated during the search, and in which the measurements might be uncertain. In accordance with the illustrative embodiment, one or more search algorithm parameters (e.g., the maximum branching factor of a search tree, a depth cutoff for a search tree, a time cutoff, a threshold, etc.) are adjusted dynamically during the search based on at least one of: the degree of uncertainty of the measurements, the variability of measurements over time (e.g., standard deviation, etc.), and the fraction of members whose measurement is better than a threshold. In addition, the illustrative embodiment enables the search space to be pruned based on these criteria.

Abstract: A method is disclosed for adaptively and intelligently partitioning traffic among a plurality of communications channels, without injecting probe traffic into any of the channels. In accordance with the illustrative embodiment, a source node transmits traffic to a receiving node via K communications channels in accordance with partition coefficients ?1, . . . , ?K, and the source node receives information regarding the quality of service (QoS) provided by each of the communications channels. The source node adjusts the values of the partition coefficients ?1, . . . , ?K adaptively based on: the current channel QoS information, prior channel QoS information, the prior values of ?1, . . . , ?K, and a measure of channel independence for one or more pairs of communications channels.

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 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 technique is disclosed that enables the adaptive pooling of M transmission paths that offer a first signal-quality guarantee, or no guarantee at all, with N transmission paths that offer a second signal-quality guarantee. Through this adaptive pooling, a telecommunications channel is created that meets the quality of service or waveform quality required for a packet stream being transmitted, while not excessively exceeding the required quality. The technique adaptively recaptures any excess signal quality from one path and uses it to boost the quality of an inferior path. A node of the illustrative embodiment selects the paths to handle a current segment of source packets, based on one or more parameters that are disclosed herein. The node adapts to changing conditions by adjusting the transmission characteristics for each successive segment of packets from the source packet stream.

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 method and apparatus are disclosed for redirecting traffic associated with an application so that the traffic advantageously traverses (or “hairpins”) through an application-layer gateway. Because the present invention advantageously redirects traffic without any participation by routers, no changes to or replacement of routers in a network is required. The illustrative embodiment is disclosed in the context of Internet telephony, but is also applicable to other kinds of applications and types of communication (e.g., Internet Protocol Television [IPTV], instant messaging [IM], videoconferencing, etc.

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 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 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 technique is disclosed that enables the adaptive pooling of M transmission paths that offer a first signal-quality guarantee, or no guarantee at all, with N transmission paths that offer a second signal-quality guarantee. Through this adaptive pooling, a telecommunications channel is created that meets the quality of service or waveform quality required for a packet stream being transmitted, while not excessively exceeding the required quality. The technique adaptively recaptures any excess signal quality from one path and uses it to boost the quality of an inferior path. A node of the illustrative embodiment selects the paths to handle a current segment of source packets, based on one or more parameters that are disclosed herein. The node adapts to changing conditions by adjusting the transmission characteristics for each successive segment of packets from the source packet stream.