Showing papers on "Loopback published in 2002"

On double-link failure recovery in WDM optical networks

Abstract: Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We consider a failure model in which any two links in the network may fail in an arbitrary order. Three loopback methods of recovering from double-link failures are presented. The first two methods require the identification of the failed links, while the third one does not. However, precomputing the backup paths for the third method is more difficult than for the first two. A heuristic algorithm that pre-computes backup paths for links is presented. Numerical results comparing the performance of our algorithm with other approaches suggests that it is possible to achieve 100% recovery from double-link failures with a modest increase in backup capacity.

Method and apparatus for frequency and timing distribution through a packet-based network

Abstract: A reference frequency is distributed through a packet-based network to remote elements in a system. Timing packets are periodically sent from a master timing element, to be received by at least one peripheral timing element. Echo messages are sent to the master timing element by each peripheral timing element after a unique delay, in response to the reception of a timing packet. Loopback delay measurements are included in each timing packet for each peripheral timing element. Each peripheral timing element locks a loop using only timing packets which incur a minimum loopback delay.

Redundant router network

Abstract: A networking system including virtually addressed devices is described. A network device has one or more virtual addresses assigned to its loopback interface. Once so assigned and the loopback interface enabled, data and commands directed to any of the assigned virtual addresses is sent through the device's protocol stack. The device is then structured to act on the data and commands destined for the virtual address.

Bit error rate tester

Abstract: A device apparatus and method are detailed that allow for improved bit error rate (BER) testing, configuration, and operation of a communication device and associated physical communication link, in particular on a HDSL communication device and link. The improved communication device apparatus and method additionally allow for the communication device to utilize an embedded BER tester (BERT) to run commonly utilized BER tests on high speed communication channels (downstream and upstream) associated with the communication device. The device apparatus and method also allow for a BER test to be configured and initiated remotely, with loopback at a remote device and masking of alarm states at the remote device or local device until the BER test is complete.

Method and apparatus for automatically detecting virtual circuit settings and encapsulation types in a DSL network

Abstract: Automatic detection of the virtual circuit setting and encapsulation type of a DSL line A DSL modem determines the correct virtual path identifier (VPI) and virtual channel identifier (VCI) by sending OAM loopback requests to different VPI/VCI pairs until a valid loopback reply is received PPPoA encapsulation is detected when a valid reply is received to a PPP LCP configuration request or echo request PPPoE encapsulation is detected when a valid reply is received to a PPP LCP termination request or a PPPoE discovery offer (a PADO packet) is received in response to a PPPoE discovery initiation request (a PADI packet)

Loop back testing for multi-protocol hybrid networks

Abstract: A hybrid network (100) includes a plurality of network elements (102, 106, 110, 114) that are coupled together by communication links (116, 118, 120, 122, 124). The network elements operate on different communications protocols. A loop back test message traverses a path (140) across network elements to test the integrity and quality of the path. Each network element that receives the loop back message modifies the message in a predetermined manner. The originator of the message verifies that the message was modified in an appropriate manner and in an appropriate time frame to determine integrity and quality.

Addressing node failures in all-optical networks

Abstract: We investigate the effectiveness of link-protection schemes in terms of their ability to handle node failures in all-optical networks. We focus on node recovery, using a ring-based scheme (double-cycle cover; DCC) and generalized loopback. Comparisons are made by introduction of metrics that measure a protection scheme’s effectiveness in handling node failures. We also introduce measures that quantify failure impact, the degree to which a network is left vulnerable to a failure after a previous failure has been successfully recovered. Comparison with DCC for five sample networks shows that generalized loopback is more robust against node failures and can provide the same level of reliability while using 16% less capacity on average over five sample networks.

Testing method and tester for semiconductor integrated circuit device comprising high-speed input/output element

Abstract: The invention relates to a test method and a test apparatus for a semiconductor integrated circuit device having a high-speed input/output device, and it has for its object to perform the test of the high-speed I/O exceeding 1 GHz, promptly by a simple board construction, without altering a test system for individual I/O specifications. A semiconductor integrated circuit device ( 1 ) having a high-speed input/output device ( 2 ) is set on a load board ( 3 ) which is provided with loopback paths ( 4 ) each connecting the external output terminal and external input terminal of the semiconductor integrated circuit device ( 1 ) by transmission lines, and the operation of the high-speed input/output device ( 2 ) is tested within the semiconductor integrated circuit device ( 1 ) by utilizing test means ( 5 ) disposed inside the semiconductor integrated circuit device ( 1 ), and the loopback paths ( 4 ).

Optical transceiver, a multiplexing integrated circuit, a demultiplexing integrated circuit, an integral multiplexing/demultiplexing integrated circuit, and method for evaluating and testing the optical transceiver

Abstract: An optical transceiver 1 comprises first and second pseudo-random pattern generators 23 and 28 for generating a pseudo-random pattern signal, which are placed in a transmitting side path 6 and in a receiving side path 11 of the optical transceiver 1, respectively; first and second pseudo-random pattern detectors 21 and 26 for evaluating an inputted pseudo-random pattern signal, which are placed in the transmitting side path 6 and in the receiving side path 11 of the optical transceiver 1, respectively; a first loopback path 31 that loops back from a multiplexing circuit 3 to a demultiplexing circuit 8; and a second loopback path 32 that loops back from a light-electricity converter 7 to an electricity-light converter 4.

Method for implementing an OAM function by exchanging request-reply packets between stations of a RPR network, and corresponding packet frames

Abstract: Described is a method extending the OAM functionality in the RPR networks through a new OAM loopback procedure of request-reply type together with the definition of a new RPR OAM loopback frame The OAM loopback function allows any RPR station to check the reachability of another RPR station It is not necessary to stop any data traffic communication on the network in order to perform this function

High speed I-O loopback testing with low speed DC test capability

Abstract: A loopback circuit for testing low and high frequency operation of integrated circuit transmitter and receiver components. First and second resistors forming a first branch of the circuit are series-connected between first and second circuit ports. Third and fourth resistors forming a second branch of the circuit are series-connected between third and fourth circuit ports. A DC isolator is connected between the first and second branches. At lower frequencies, the two branches are DC-isolated, enabling ATE-measurement of the transmitter's output drive level independently of the receiver, continuity testing of ESD protection structures, etc. At higher frequencies, the transmitter's output signal is split into three portions, each of which is attenuated by a selected amount. One of the attenuated signal portions is applied to the receiver to test the receiver's sensitivity, independently of possible excess resiliency in the transmitter's output drive level.

Transceiver circuit arrangement and method

Abstract: A doubly balanced transceiver system having a transmit terminal (TX), a receive terminal (RX), and an an antenna terminal (ANTENNA), 180° hybrids ( 201, 240 ), 90° hybrids ( 204, 304, 235 and 335 ), a power amplifier ( 230, 330 ) and a RX/TX switch ( 220 ) for disabling the power amplifier so that signals received at the transmitter are reflected to the receive terminal (RX). The 180° hybrids ( 201, 240 ) preferably split and re-combine signals into parallel paths. A loopback test mode is preferably provided by use of an antenna isolation switch ( 302 ) to enable a power detect terminal (POWER_DETECT). This eliminates pricey and problematic GaAs switches, and allows the use of low cost silicon for the power amplifier. The doubly balance architecture also has the advantage of eliminating common-mode noise, and reflection problems with the PA gain stages. Additionally, greater power can be extracted from the power amplifier. Further the arrangement has less insertion loss compared to a GaAs switch. Also, dependant upon system specifications, it may be possible to eliminate harmonic filtering at the power amplifier output.

Physical layer and physical layer diagnostic system with reversed loopback test

Abstract: A physical layer and a physical layer diagnostic system allow the physical layer of a network device to be tested without requiring the physical layer to be connected to a medium access controller. The physical layer includes a medium-side interface. A plurality of digital circuits in the physical layer communicate with the medium-side interface. A medium communicates with the medium-side interface. A packet generating device is connected to the medium and generates data packets that are transmitted over the medium to the medium-side interface, through the plurality of digital circuits of the physical layer and back to the packet generating device.

System and method for conducting diagnostics in a telecommunications node

Abstract: A system and method for conducting diagnostic tests on a network card disposed in a telecommunications node. A diagnostic application automaton is launched at predetermined intervals by a base level diagnostics automata under the control of an executive scheduler running on the network card, wherein the network card is initially in a provisioned configuration mode operable to transmit and receive communication traffic therethrough. Upon determining by the base level diagnostics automata to install the diagnostic application, the network card is reconfigured into a loopback configuration mode involving a predefined loopback path in the telecommunications node. Operations relating to the telecommunications traffic are suspended in the loopback mode, whereby one or more diagnostic tests may be performed by the installed diagnostic application by injecting appropriate test patterns at specific locations in the path. Upon completing the diagnostic tests, the network card is reconfigured into the provisioned configuration mode in order to commence the communication traffic.

Practical active packets

Abstract: Active networking adds programmability to the network infrastructure to promote service introduction. One approach involves active packets that carry programs rather than standard passive headers. To date, no one has proposed an active packet system that is truly practical: providing added flexibility over passive packet schemes without sacrificing either safety or efficiency. In this work, we propose a new system, SNAP (Safe and Nimble Active Packets), that strikes a useful balance. First, SNAP is safe. We use a combination of language design (limited expressiveness) and safe interpretation techniques that allow us to show that SNAP exhibits robustness (resistance to malicious or buggy code), isolation (non-interference with other packets), and resource predictability. In particular, we prove that each execution of a packet program consumes at most an amount of CPU and memory resources that are linearly proportional to the program's length; we also show the total number of packet executions that can be caused by a packet or its descendents is bounded. Second, SNAP is efficient. We designed the SNAP packet format to minimize memory overhead: most packets can be executed in-place in kernel network buffers. We show experimentally that SNAP latency and bandwidth microbenchmarks perform within a few percent of their IP-family counterparts in software routers connected by 100 Mb/s Ethernet links. SNAP incurs extremely low overhead: IP-like functionality is available at IP-like performance. Finally, SNAP is flexible, despite the fact that we have limited its expressiveness. We briefly describe a compiler that translates PLAN (an earlier active packet language) into SNAP using a combination of function inlining and sending copies of the current packet over a node's loopback interface to emulate backward branches. Since this loopback technique consumes one unit of resource bound, we find that the resource bound field of the packet is a convenient knob for trading off tight bounds on global resource usage for increased flexibility (in terms of the amount of looping available to the packet). We also describe two new native SNAP applications: distributed denial-of-service attack detection and active video-on-demand.

Optical reception fault diagnostic method, and optical transmission system provided with optical reception fault diagnostic function

Abstract: PROBLEM TO BE SOLVED: To provide a method that can easily discriminate whether a fault location exists in a station or in a device and further in a transmitter or in a receiver through remote location, on the occurrence of an optical interruption fault and to provide an optical transmission system. SOLUTION: A center 3 can easily discriminate whether a fault location exists in a transmission line 50 or in optical transmission systems and further in an optical transmitter 10 or in an optical receiver 20, through its remote control on the occurrence of an optical interruption fault by providing an optical switch 30 to an input section of an optical signal and an optical branch 40 to an optical output section in both bidirectional optical transmission systems 1, 2 so as to provide a loopback function of input and output lights.

Loopback test method and device

Abstract: PROBLEM TO BE SOLVED: To provide a loopback test method that can be executed online. SOLUTION: In a system that is provided with computers 11, 12,..., each having a loopback test function and a line concentration device (HUB) 31 having ports 1, 2, etc., connected to the computers through a twisted pair cable 21 having a transmission line 211 and a reception line 212, each port has an SW1 that connects the transmission line and the reception line, and a communication control section 3111 that issues a test request in the absence of transmission reception data from a computer connected to itself and other ports, the SW1 is connected when receiving an ACK from the computer to conduct a test from the computer. The HUB 31 has a buffer that temporarily stores data received from the other port during the test.

Method and system for performing a logical loopback test

Abstract: Systems and methods for obtaining logical layer information in a frame relay and/or asynchronous transfer mode (ATM) network are described. In an exemplary embodiment, a physical layer test system, such as an integrated testing and analysis system, communicates with a broadband network management system, which in turn communicates with an element management system for a frame relay and/or ATM network.

Signal transmit-receive device, circuit, and loopback test method

Abstract: A signal transmit-receive device that reduces the number of high-speed signal lines required for connecting a transmitting circuit group and a receiving circuit group and for running a loopback test on a signal transmit-receive device for signal communication, and reduces installation costs and power consumption. The new loopback test circuit uses an error detecting circuit within the transmitting circuit IC, a test signal producing circuit within the receiving circuit IC, and a wiring for transmitting error information from the transmitting circuit to the receiving circuit. The error detecting circuit compares a test signal pattern defined in advance by a first communication device and a received signal pattern to detect errors. The test signal producing circuit produces a test signal pattern defined in advance by the first communication device, and can invert any bits of the test signal pattern, based on error information. During a loopback test, if an error is detected in the error detecting circuit, the error signal is transmitted to the test signal producing circuit of the receiving circuit through the wiring. The test signal producing circuit produces a predetermined test signal pattern if the error signal DE has an L level; upon receiving H level, it sends back to the first communication device the predetermined test signal pattern having at least one inverted bit based on information in the error signal.

External loopback test mode

Abstract: A method and apparatus for testing the transmitter and receiver links of an I/O node. A test mode in an I/O node is initiated by a test signal driven from a test system to the I/O node via a loadboard. The I/O node may then receive test data through a peripheral bus interface. The inputting may be performed synchronously to a first clock signal. The I/O node may then transmit the test data to a receiver via a loopback mechanism on the loadboard. The transmission and reception of test data between transmitter and receiver is synchronous to a second clock signal, which has a frequency equal to the operational frequency of the transmitter and receiver. The receiver may forward the test data to the peripheral bus interface, which may in turn output the test data to the test system. The test system may then determine the results of the test.

Ultrasonic doppler diagnostic device

Abstract: PROBLEM TO BE SOLVED: To provide a means of automatically removing the loopback phenomena in an ultrasonic Doppler diagnostic device. SOLUTION: The loopback circuit 30 compares the measured data of Doppler displacement frequency housed in a memory circuit 10 at the mutually adjacent measurement point and judges that the loopback phenomenon occurs from the discontinuity of the measured data when the Doppler deviation frequency shows changes more notably than the specified threshold. The generation rate counting circuit 32 counts the incidence of loopback phenomena according to the detection signals outputted when the loopback phenomena are detected by the loopback detection circuit 30. The incidence discriminant circuit 34 compares the incidence obtainable from the generation rate counting circuit 32 with a single or plural thresholds and judges the incidence level of loopback phemenona in order to automatically adjust the PRF based on the judged results thereof.

Inter-lan connection system and its loopback test system

Abstract: PROBLEM TO BE SOLVED: To provide an inter-LAN connection system that can effectively carry out a loopback test from a communication company to a termination point of a subscriber in the case of connecting a user LAN to a broadband LAN of the communication enterprise via an optical fiber transmission line. SOLUTION: An optical conversion bridge 40 of the enterprise transmits a start packet whose length is shorter than a packet length of an Ethernet (R) frame to a subscriber side optical conversion repeater 50 via the optical fiber transmission line 20 in the case of conducting a loopback test. Thus, the optical conversion repeater 50 sets its electric physical layer termination section 510 with respect to the user LAN to a loopback state and transmits a reply packet in response to the start packet to the optical conversion bridge 40. The optical conversion bridge 40 receiving the reply packet transmits a test packet with a length equal to that of the Ethernet frame to the optical conversion repeater 50 via the optical fiber transmission line 20. The test packet is looped back at the electric physical layer termination section 510 of the optical conversion repeater 50 and looped back to the optical conversion bridge 40 via the optical fiber transmission line 20. The result is indicated by a blinked LED 429 or reported to a remote controller.

Method and system for handling a loop back connection using a priority unspecified bit rate in ADSL interface

Abstract: A new format for asynchronous transfer mode defines a priority unspecified bit rate format; which uses the same memory structure as that used by the existing UBR and CBR traffic protocols. This format is also used for a loopback operation.

Physical layer device with diagnostic loopback capability

Abstract: A physical layer communications device including a receiver connected to a physical channel. A transmitter is also connected to the physical channel. A selector reflects a packet received by the receiver from a remote sender over the physical channel back to the sender when the physical layer communications device is in a diagnostic mode.

Loop test apparatus and method

Abstract: Systems and methods are described for measuring the quality of telephone transmission lines. A device, such as a loop test apparatus, can be located at a customer's premises and used for remotely diagnosing telephone line impairments, especially concerning the local loop and customer premises wiring. Such a device is valuable for determining if a telephone line is suitable for new services, such as DSL. The loop test apparatus can incorporate an integrated local loopback feature that can be controlled from a loop testing server (LTS) at, e.g., a telephone Central Office. The loop test apparatus can terminate a telephone line at the customer premises based on a message sent by the LTS. The local loopback will then reflect signals transmitted by the LTS back to the LTS so that line characteristics of the local loop and customer premises wiring can be analyzed, without the need to dispatch telephone company service equipment and/or personnel to a customer premises.

Method and system for loop-back testing in multi-protocol hybrid networks

Abstract: A hybrid network (100) includes a plurality of network elements (102, 106, 110, 114) that are coupled together by communication links (116, 118, 120, 122, 124). The network elements operate on different communications protocols. A loop back test message traverses a path (140) across network elements to test the integrity and quality of the path. Each network element that receives the loop back message modifies the message in a predetermined manner. The originator of the message verifies that the message was modified in an appropriate manner and in an appropriate time frame to determine integrity and quality.

Transmission distance measuring method and apparatus using signal loopback in optical transmission module for imt-2000 digital optical repeater

Abstract: PURPOSE: A transmission distance measuring method and apparatus using a signal loopback in an optical transmission module for an IMT-2000 digital optical repeater are provided to simply measure a distance by generating a pulse and measuring time taken from a point when the pulse is returned through a signal loopback at a remote station to a point when the pulse signal comes back. CONSTITUTION: An optical signal received from upward is changed to 16 144 Mb/s signals through an optical repeater(201) and a 1:16 demultiplexer(202), and an overhead and a payload bit are demultiplexed through a reframer(204). The 16 155 Mb/s signals including a pulse bit are inputted to the reframer(204) and simultaneously to a16:1 multiplexer(210), and then transmitted to the next remote station. As for the pulse bit extracted by an overhead processor(208), if a pertinent remote station is an object for a distance measurement, a loopback switch(206) is connected by controlling a distance measurement pulse loopback of a remote station NMS(Network Management System) and then the pulse bit is returned reversely through an OR gate(207). The returned pulse bit gets back to a distribution station. If the pertinent remote station is not an object for distance measurement, the OR gate(207) passes the pulse bit inputted reversely through a reframer(209).

Band reservation method, and system

Abstract: PROBLEM TO BE SOLVED: To provide a band reservation system that simplifies node units. SOLUTION: Transmission terminals 1, 2 insert a band reservation signal to an FRM(Forward Resource Management) cell and transmit the resulting cell, and relay nodes 3, 4 have only to discriminate whether or not number of VC(Virtual Channels) stored in a reserved FRM cell VCI(Virtual Channel Identifier) storage circuit 15 is N or below and accept band reservation of N connections for forward transmission channels. Furthermore, the relay nodes 3, 4 have only to handle number of the connections and need not to compare a remaining transmission channel band with a reserved band. Furthermore, the FRM cell, whose path in the system is the same as that of a data cell, is used for the band reservation processing. Loopback circuits 18 of the reception terminals 5, 6 return the FRM cell to the transmission terminals 1, 2 as a BRM(Backward Resource Management) cell. It is also possible to decrease a block rate by selecting a higher N for the relay transmission channel span.

Semiconductor integrated circuit and optical communication module

Abstract: PROBLEM TO BE SOLVED: To provide an optical communication module that integrates a transceiver circuit mounted on itself as an integrated circuit without using a discrete component such as a loopback IC, whose operation test and adjustment can easily be conducted, and that provides ease of module design. SOLUTION: The semiconductor integrated circuit (100) for communication of this invention is provided with a reception circuit section (100) that demultiplexes serial signal of a plurality of multiplexed signals received from the outside into signals of each channel, outputs them to the outside, and detects a change in the received signals to generate a clock signal, and with a transmission circuit section (120) that applies time division multiplexing to the serial signals of channels received from the outside and outputs the resulting signals to the outside, is provided with a loopback path (170) that feeds back the signals demultiplexed by the reception circuit section to a transmission line on the input side of the transmission circuit section and with selectors (161, 162) that can switch the signal line to the loopback path.

DCC loop plug

Abstract: Systems and methods are disclosed for testing the functionality of a synchronous optical network having a data communication channel therein. The system includes a testing device connected to a network node within the synchronous optical network and a data communication channel loop back plug connected to the testing device for returning to the synchronous optical network, any signals within the data communication channel received at the testing device. A method is also disclosed for testing a synchronous optical network having a data communication channel therein.