Concurrent LPDA-2 tests

The purpose of these tests is to test the local and remote modems and get modem status information.

Test description

Use this option to run the Verify Link; it supports the LPDA-2 (VFYLNKLPDA) command. The concurrent LPDA-2 tests let you retrieve information from the data circuit-terminating equipment (DCEs). DCEs can be analog (modems) or digital (combined data service units (DSUs) and channel service units (CSUs)). You can get information from four tests:
  • DCEs and line status
  • DCEs and line test
  • Analyze line
  • Send and receive test

You can run the LPDA-2 tests on a line while applications are using the line. The tests do not interrupt communications but temporarily slow the data transfer.

The following restrictions apply to these tests:
  • The DCEs must be compatible with LPDA-2.
  • You can run the tests only on non-switched synchronous data link control (SDLC) lines.
  • For multiport DCEs, the DCEs and Line Status test does not interrupt normal communications. The other LPDA-2 tests might interrupt normal communications.
  • You cannot run the tests on an active secondary line. A line is secondary if its data link role is either secondary or is negotiable and has negotiated to a secondary role. A line is active if a controller description under the line is varied on.

The DCEs and line status and DCEs and line test options are two modes of the same LPDA-2 request.

The DCEs and Line Status test reports parameters that the local and remote DCEs monitor during normal communications.

The DCEs and Line Test reports these parameters, runs internal tests, and reports the results. If poor line conditions are causing problems at normal speed, this test is sent over the communications line to the remote DCE at a slower transmit speed.

These two tests return the following information:
  • Configuration summary

    This includes DCE type and model, address, operating mode, transmit speed, network function, LPDA-2 code level, switched network backup (SNBU) status, data terminal equipment (DTE) interface connection, and installed features.

  • DCEs and line parameters

    These include receive level, number of received line signal detector (RLSD) losses, line quality, number of line errors, ages of remote DCE power-off and failure, ages of local DCE reinitialization and error conditions, DCE idle condition, base DCE in error, and features in error.

  • Remote DCE interface status
    This reports the current status and previous activity of the signals on the DTE interface lines attached to the remote DCE. The DCE monitors the following signals:
    • Request to send
    • Ready for sending
    • Transmit data
    • Receive data
    • Received line signal detector or carrier detect
    • Data signalling rate selector
    • Data terminal ready
    • DTE power loss detected
    • Test control

You can run the Analyze line test only on analog DCEs (modems). The test causes the modems to exchange test patterns on the line. The modems measure parameters of the analog signals. The modems report:

  • Frequency shift
  • Second and third harmonic distortion ratios
  • Signal to noise ratio
  • Phase jitter
  • Receive level
  • Transmit level
  • Round trip delay time
  • Modem type, model, address, and transmit speed
  • Number of line errors and RLSD losses

The modem returns acceptable limits for some of the parameters.

The Send and receive test causes the DCEs to exchange several blocks of test patterns and track the errors that occur during transmission. The test reports the following:
  • DCE type, model, address, and transmit speed
  • Signal lost condition
  • Worst line quality
  • Number of line errors
  • The number of blocks that are sent, received, and in error
Parent topic: Communications tests


Last updated: Wed, June 19, 2019