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Newsletter: HDLC Link Impairment Utility a
New Data Transmission Testing Tool

High Level Data Link Control, or HDLC, is a data transmission technique commonly used over T1 and E1 lines for protocols such as LAP-D, ISDN, SS7, V5.x and GR-303. Other protocols that also use HDLC are LAP-B, LAP-F, PPP, X.25 and Frame Relay. Testing these protocols for conformance and accuracy requires simulation of impairments that are common during data transmission.

GL has recently added HDLC Link Impairment Utility (HLIU) to its suite of HDLC testing tools for T1 and E1 lines. The HLIU software offers various options to 'impair' (inject errors) to specific HDLC frames of a real time HDLC stream. In this way, proper protocol behavior in the presence of such errors can be verified.

HLIU Features:

  • Logic Error Insertion and CRC Error Insertion.
  • Frame manipulation operations such as Drop a HDLC Frame, Change HDLC Frame Order, Duplicate a HDLC Frame, Insert a Frame and Delay a Frame.

The input stream of HDLC frames may be contained in a 'single' 64 kbps channel (one timeslot) or in 'N x 64 kbps' hyperchannel (N timeslots). The output stream of HDLC frames is contained in a similar structure of single or multiple timeslots. The output stream of HDLC frames may be on a different card or the same card as the input, different timeslots or the same timeslots as the input, or on a greater number of timeslots than the number of timeslots on the input.

The HLIU application works with Single and Dual PCI T1, Single and Dual PCI E1 Cards. The HLIU also works with Single and Dual Laptop T1 or E1 units. The HLIU application can be tested with the 'HDLC Playback File' and 'HDLC Analysis' testing tools already available from GL Communications.

Please review the HDLC Link Impairment Utility and give us a call if you are interested in GL's products/software for this or other applications. We would be happy to consult with you on solutions to your testing needs and we look forward to hearing from you.

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