GL Announces Conformance Test Suite for ISDN Protocols

Welcome to another September 2014 issue of GL's Newsletter providing information and insight into our latest product - MAPS™ ISDN and LAPD Protocol Conformance Test Suite.

ISDN Protocols


The ISDN network is an integrated solution for providing basic telephony and data services, and additional supplementary telephony services. The user-to-network interface is provided in two flavours:

  • Basic interface structure - two B-channels and one 16 Kbit/s D-channel (2B+D)
  • Primary rate B-channel interface structure - 30 B-channels and one 64 Kbit/s D-channel, (30B+D)

From the point of view of the OSI architecture, an ISDN line has a stack of three protocols

  • Layer 1 - Physical Layer
  • Layer 2 - Data Link Layer (known as LAPD protocol)
  • Layer 3 - Network Layer (known as ISDN protocol)

In order to provide reliable communication over the network, it is essential for the protocol implementation to be checked for conformity to its standard specifications.

GL's new product - MAPS™ ISDN and LAPD Conformance test suite helps service providers to check their ISDN network for conformity to its standard specifications - ITU-T Q.931 for ISDN and Q.921 for LAPD.

In addition, one can also use MAPS™ ISDN test tool to test ISDN signaling specification as per other standards such as the 5ESS, 4ESS, BELL, DMS-100, DMS-250, SR-4994, and QSIG ECMA standards.

The MAPS™ ISDN and LAPD Conformance test suite can conform various ISDN and LAPD call states. See table below that details call states.

The ISDN Conformance test suite is used to perform automated verification of protocol conformance of an ISDN device or switch, offering a complete solution for testing, troubleshooting, and maintenance of devices and networks implementing PRI ISDN. It is useful to test ISDN products designed for either U or S/T interface, including network terminations, Type 1 terminating equipment, and terminal adapters.

The application supports powerful utilities like Message Editor, Scheduler, Load Generation, Statistics, and Reports to further help testing process.

ISDN Protocol Stack Implementation

ISDN Protocol Stack

ISDN Protocol Stack


  • Supports Switch and Subscriber conformance tests
  • Example Scenarios in ISDN conformance Test Suite
    • Verification of Device behaviour for valid, invalid and inoppurtune events in a given state
    • Verification of Bearer capability negotiation
    • Verification of device behaviour for valid and invalid Information elements
    • Verification and Validation of protocol related timers
    • Sequence Number Verification in Lap-D
    • Verification of Re-Transmission of messages in a given state
  • ISDN & LAPD simulation over TDM (T1 E1)
  • Multiple T1 E1 line interfaces supported
  • Access to all ISDN Message Parameters such as Call Reference Value, Called Number, Calling Number, Release Cause, and more
  • Provides various release cause codes such as rejected, no user response, user busy, congested, and so on to troubleshoot the problems in ISDN
  • Send/receive traffic over established calls - PCM voice files, DTMF/MF digits, and tones
  • Ability to generate high volumes of ISDN traffic
  • Supports NFAS testing for T1 only
  • Provides fault insertion, and erroneous call flows testing capability
  • Bulk Call Simulation for Performance testing, Load testing, Functional testing, and Regression testing of network elements

Call Simulation

Typical ISDN Signaling Procedure

ISDN Call Messages

ISDN Call Messages

ISDN Conformance Test - Examples

Example 1: Null State (U00) Call State Conformance

ISDN U0 Null Call State Conformance Test - From Switch Side

ISDN U0 Null Call State Conformance Test – From Switch Side

As an example, the conformance script below is used to test the Null State of the DUT. The DUT in the Null call state, on receipt of a RELEASE COMPLETE message, is expected to send no message and remain in the Null call state. The MAPS™ then sends status enquiry to the DUT to conform the Null State.

Example 2: Outgoing Call Proceeding (U03) Call State Conformance

ISDN U03 Call Proceeding Call State Conformance Test – From Switch Side

ISDN U03 Call Proceeding Call State Conformance Test – From Switch Side

The conformance test script ensures that the DUT in the Outgoing Call Proceeding call state U03, on receipt of an ALERTING message, sends no message and enters the Call Delivered call state U04. MAPS™ can verify the DUT status by sending Status Enquiry request message thus conforming the call state.

Test Reports

Compliance Test PDF Report

Compliance Test PDF Report

Conformance test reports are created in the Results folder corresponding to each node (Subscriber or Switch) after the test bed is successfully executed and terminated. The reports are available in XML and PDF formats.

For comprehensive information on the application, you can refer to the MAPS™ ISDN and LAPD Protocol Conformance Test Suite web page.

Other ISDN Test Products
GL also provides a host of other ISDN Test Products as listed below -

ISDN over T1 or E1 ISDN over IP Network Surveillance and Monitoring

Back to Newsletter Index Page Back to Newsletter Index Page