T1 E1 Testing

HDLC Playback Applications


GL's HDLC Playback application is used to transmit HDLC frames in the pre-recorded files (*.hdl) over T1/E1 channels. The frames can be transmitted on selected time slots (contiguous or non-contiguous), sub-channels or full bandwidth. The HDLC frames may also be transmitted on just one, or n x 64 kbps, or n x 56 kbps hyper channels.

Further, the application also provides the option to reverse or inverse bits in the selected data during transmission.

Main Features

  • Transmit HDLC frames in the pre-recorded files (*.hdl)
  • HDLC frames can be transmitted on either a single channel (64 or 56kbps), hyper channels (N*64 or N*56kps), or sub channels (n*8kbps)
  • Supports continuous repeated file transmission.
  • Supports limited play option to transmit the HDLC file as required
  • With "revert bits" feature the bit order of each byte is reversed before transmission.
  • With "invert bit" feature each bit in every byte transmitted or captured is toggled 1 to 0 or 0 to 1.
  • Allows inserting flags between the frames
HDLC Playback Applications

Working with HDLC Playback

  • Continuous - The HDLC frames contained in the file are transmitted continuously into the HDLC data channel.

  • Limited  - Transmission of HDLC frames is limited to the defined number entered in the Limited field. After the defined number of frames is transmitted, trailing flags are transmitted and transmission of HDLC frames ceases.

  • Revert Bits
    Applies Octet bit reversion when enabled. Octet bit reversion changes order of bits in each octet in such a way that the most significant bit becomes the least significant bit. For example, 0101001 is changed to 1001010.

  • Invert Bits
    Applies Octet bit inversion when enabled. Bit inversion changes each bit in received octets from 0 to 1 and 1 to 0.

  • Flags between Frames
    Allows definition of the number of flags between consecutive HDLC frames.

  • Unused Fractional Bits
    When the data transmission rate is selected either as Nx56 Kbps (Bits 1-7) or Nx56 Kbps (Bits 2-8) , the data is transferred leaving one bit of each unused channel. This is referred to as unused fractional bit and value can be set to either 0 or 1.

  • Channel Bandwidth
    Allows selection of data transmission rate (64 or 56 kbps). If eight bits out of eight are used for data transmission, then this is referred to as 64 kbps format.  If seven bits out of eight are used for data transmission, then this is referred to as 56 kbps format.
HDLC playback Continuous limited playack

Test Scenario

For example, using HDLC Playback, a sample HDLC '3to102byteLEN.HDL' file can be continuously played on Card #1 timeslot 23, with N x 8 and bits (1 – 3) option selected. Notice that only one HEX nibble is changing in the 23 rd time slot. The other nibble is not changing because HDLC data is being transmitted only into 23 timeslot that forms one nibble.

HDLC playback test scenario