Abstract: The network failure detection apparatus is realized as a function of a terminal in a network. The network failure detection apparatus acquires packet reception statistic information on a port-by-port basis of a relay unit, and extracts a port having a large amount of packet reception per unit time. When there is one port having a large reception amount in a certain relay unit, the network failure detection apparatus decides that the L2 (layer 2) loop is occurred in the downstream direction of the port concerned. Also, when there are two ports having a large reception amount in a certain relay unit, the network failure detection apparatus decides that a loop is formed at the relevant two ports, in which the L2 loop is occurred.

Abstract: In a relay device or the like in which a speed changes from a high speed to a low speed, a packet residence (packet transfer wait) occurs when a packet string in which packet intervals are shortened arrives. When a packet discard occurs before passing through the relay device or the like, a packet interval having been lengthened by the packet discard is shortened by the relay device or the like for transferring packets. When a packet discard occurs after passing through the relay device or the like, a packet interval having been lengthened by the packet discard remains unshortened for transferring packets. Therefore, by observing at terminals the packet discard and the packet interval on the occasion of the packet discard, whether the packet discard has occurred in the high speed section or the low speed section is specified.

Abstract: A request-packet transmitting unit transmits a predetermined number of request packets having a non-unicast destination address that can be received by a target network including a network identified by a first network address, from a monitoring network identified by a second network address different from the first network address through a layer 3 relay device. A layer 2 loop detecting unit receives response packets corresponding to transmitted request packets through the layer 3 relay device, and detects a layer 2 loop in the target network based on number of received response packets and number of transmitted request packets.

Abstract: A L2 loop failure location generated in any one of a plurality of search target apparatuses disposed in network is detected in a short time. A network failure location detecting apparatus executes the steps of broadcasting packets with a plurality of different source MAC addresses; acquiring statistical information that is information of a learning port of the plurality of different source MAC addresses learned by each of the plurality of search target apparatuses; finding whether the number of the learning ports of the plurality of different source MAC addresses is one or two from the acquired statistical information; and determining that the L2 loop failure location is the search target apparatus including two learning ports of the plurality of different source MAC addresses.

Abstract: A network fault detection apparatus, which detects L2 loops due to L3 bridge connections, is provided. A network fault detection apparatus acquires physical addresses corresponding to the network addresses of at least two nodes among the plurality of nodes constituting a network, and by detecting the existence of a plurality of physical addresses for network addresses of the two nodes, and detecting the existence of a physical address common to network addresses thereamong, detects an L2 loop caused by an L3 bridge connection, which induces a network fault.

Abstract: A computer-readable recording medium recording a program capable of accurately analyzing the cause of a performance fault at the very end point of a client system, server system, etc. Outgoing and incoming packets are captured during execution of a communication application to measure a round trip time, and a communication window size of the transmitting source is estimated based on the captured incoming packets. A throughput estimate is calculated from the round trip time and the communication window size, and the estimated value and actual measured value of the throughput are displayed on, for example, a display, together with various other communication parameters including the communication window size and the round trip time, whereby the cause of a performance fault can be accurately located by quantitative analysis.

Abstract: A network failure detection apparatus is realized as a function of a terminal in a network. The network failure detection apparatus transmits reachability confirmation packets to a terminal of search object. From a reachability condition decided on the basis of the receiving condition of response packets responding to the reachability confirmation packets, it is decided whether there is an L2 loop occurred on a path to the terminal of search object.

Abstract: The network failure detection apparatus is realized as a function of a terminal in a network. The network failure detection apparatus acquires packet reception statistic information on a port-by-port basis of a relay unit, and extracts a port having a large amount of packet reception per unit time. When there is one port having a large reception amount in a certain relay unit, the network failure detection apparatus decides that the L2 (layer 2) loop is occurred in the downstream direction of the port concerned. Also, when there are two ports having a large reception amount in a certain relay unit, the network failure detection apparatus decides that a loop is formed at the relevant two ports, in which the L2 loop is occurred.

Abstract: A full duplex/half duplex mismatch is detected by a full duplex/half duplex mismatch detecting apparatus connected through a network to a host. The loss rate of the transmission of a check messages is compared according to a sequential transmission pattern and the loss rate of the transmission of the check message according to divided transmission patterns by the full duplex/half duplex mismatch detecting apparatus, and if the loss rate of the transmission of the check messages according to the sequential transmission pattern is the larger, a full duplex/half duplex mismatch is determined to be present on the network path.

Abstract: In a communication system, transmission/reception of data can be performed between end hosts connected to a relay switch in a subnet even in an improper connection at a L2 level in the relay switch in a communication. Communication failure due to a packet loop generated by the improper connection of the L2 level is recovered by wherein the packet loop is stopped by continuously transmitting long-size MAC packets longer than a packet generating the packet loop into the subnet, which have destinations as a broadcast MAC address or multicast MAC address.

Abstract: Disclosed is a communication control method for recovering communication failures caused by a packet loop that occurs as a result of L2-level misconnection at relay switches in a communication system where data transmission/reception is carried out between a plurality of end hosts connected to the relay switches within a subnet. The method includes the steps of consecutively sending packets each having, as its originator address, a MAC address other than an originator MAC address of an end host desired to be communicated making up the subnet; thereby stopping the packet loop; and then sending packet data using, as a destination MAC address, a MAC address of a destination end host.

Abstract: A network looping detecting apparatus has an increased real-time operation capability for network looping detection and also has scalability. The network looping detecting apparatus has a count information acquiring unit for periodically acquiring count information which is counted up when the lifetime of a packet has elapsed, from a network device of a network to be monitored for network looping. The network looping detecting apparatus also has a looping detecting unit for detecting network looping from the count information. Specifically, the network looping detecting apparatus detects network looping based on the fact that when a packet loops due to network looping, the lifetime of the packet elapses, and the count information is counted up.

Abstract: A computer-readable recording medium recording a program capable of accurately analyzing the cause of a performance fault at the very end point of a client system, server system, etc. Outgoing and incoming packets are captured during execution of a communication application to measure a round trip time, and a communication window size of the transmitting source is estimated based on the captured incoming packets. A throughput estimate is calculated from the round trip time and the communication window size, and the estimated value and actual measured value of the throughput are displayed on, for example, a display, together with various other communication parameters including the communication window size and the round trip time, whereby the cause of a performance fault can be accurately located by quantitative analysis.

Abstract: In a relay device or the like in which a speed changes from a high speed to a low speed, a packet residence (packet transfer wait) occurs when a packet string in which packet intervals are shortened arrives. When a packet discard occurs before passing through the relay device or the like, a packet interval having been lengthened by the packet discard is shortened by the relay device or the like for transferring packets. When a packet discard occurs after passing through the relay device or the like, a packet interval having been lengthened by the packet discard remains unshortened for transferring packets. Therefore, by observing at terminals the packet discard and the packet interval on the occasion of the packet discard, whether the packet discard has occurred in the high speed section or the low speed section is specified.

Abstract: For controlling a traffic on a network including a plurality of links, the apparatus includes a collecting unit that collects information on the traffic for each of the links periodically; an acquiring unit that acquires basic data collected from a link for a predetermined period; and a predicting unit that predicts a future traffic on the link based on the basic data. The start time of the predetermined period is the time when the latest control of the traffic was performed on the link or other link adjacent to the link.

Abstract: A content adaptation service control system includes a content adaptation server device for carrying out a predetermined content adaptation service for original content data retained in a content server device in response to a content data acquisition request given from a client device utilized by a user, an edge device, in a network, judging a necessity for, when receiving the content data acquisition request from the client device, starting the content adaptation service and notifying of a startup request, and a service control device determining, when notified of the startup request from the edge device, a mode of the content adaptation service that should be carried out by the content adaptation server device on the basis of contract information about the user subscribing the content adaptation service, and transmitting the determined mode of the content adaptation service as a processing request to the edge device.