Integrated Services Digital Network Integrated Services Digital Network 207 in Software

Creation Code 128 in Software Integrated Services Digital Network Integrated Services Digital Network 207

Layer 2 frame (LAPD)

Figure 99 The components of the Q931 message are called information elements Depending upon the type of message, some information elements are mandatory, while others are optional

Q931 groups messages into four categories:

Call Establishment (examples Connect, Setup, Alerting) Call Information (examples Resume, Suspend) Call Disconnection (examples Disconnect, Release, Restart) Miscellaneous are used to maintain and control the network connection; examples are Facility, Notify, Status Figure 910 illustrates a possible ISDN call setup procedure with Q931

Tools and Measurements for ISDN Networks Testing of ISDN devices and networks occurs in three main areas relating to the design and deployment of these devices: research and development, installation and commissioning, and maintenance

The first category of ISDN test-tool users includes ISDN equipment and network developers, who are involved in the design of Customer Premise Equipment (CPE) such as terminals, TAs, NT devices, and CO switches Usually the design process is divided into stages or pieces; development testing occurs at many stages in this Each stage or piece must be tested for functionality and to verify that the design is operating properly

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Info (digit)

Info (digit)

Figure 910 This diagram describes a typical sequence of Q931 messages transmitted on the D channel to

establish a voice call on a B channel Depending on the implementation of Q931, additional or fewer messages may be sent

Toward the end of the development cycle, implementation testing is performed on the entire design Implementation testing consists of verifying that the design meets the ISDN standards it incorporates: performance, conformance, and certification tests This ensures that the design will interoperate with other equipment when it is installed Protocol testing is a key part of this, using conformance test suites, etc As a design moves to manufacturing, other tests may be performed to verify functionality and ensure that quality units are shipped to customers The second and third categories of people in ISDN testing includes network and equipment installers and maintenance groups These people are responsible for installing the ISDN networks and equipment, debugging the networks, and keeping them up and running Most organizations have an escalated or tiered support philosophy Relatively simple tasks of installing equipment are accomplished by lessskilled personnel who use simple, low-cost tools; this often is termed Tier 1 support If problems occur that are beyond the scope and skill set of the technician, then the technician would call the next level of support, often called Tier 2 These people will have more comprehensive training and experience and more sophisticated test tools, such as protocol analyzers There might even exist a Tier 3 support team, who are considered experts in their disciplines During equipment installation, tests can be performed to verify the functionality of the equipment being installed These tests can consist of matching the equipment configurations to the network parameters Tests also may be performed to resolve interoperability and compatibility issues with new equipment After the equipment has been installed and is running, the network maintenance group will troubleshoot problems by isolating the cause of the problem and checking out the faulty equipment People involved with installation and maintenance testing are usually the network or data technicians

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Equipment and network installation and maintenance for ISDN involves similar concepts and problems as research and development, particularly when problems are protocol-related For this discussion, the ISDN problem solving will be mainly focused on installation, commissioning, and maintenance of ISDN equipment and networks Problems with ISDN equipment and networks can occur at layers 1, 2, or 3 It is useful to separate these problems into connection problems and configuration problems As with non-ISDN circuits, there are three basic areas of testing for ISDN circuits