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UM380 03 010
InterChange iQ 2000 and iQ 2000plus
6.3 Q.931/DPNSS Conversion Configuration
6.3.1 Port 1 (Q.931 port) Configuration
Layer 2 Configuration (Q921)
The default setting of the Q.931 port at Layer 2 (Q.921) is USER End. This must be
configured with inverse orientation to the attached equipment/network.
As default, the Interchange iQ 2000 causes a Layer 2 RESET on recovery after physical
layer failures. This causes all calls to be cleared when a Channel 0 fault is notified.
Alternatively, the Interchange iQ 2000 can be configured to ignore Layer 1 fault indications
and rely on periodic Layer 2 status polling to detect link problems.
The window size, used in Q.921 LAPD signalling, may be configured for each port. The
default value of 7 interworks with the majority of Q.931 networks and equipment. Alternative
values, between 1 and 127, can be set if necessary.
Layer 3 Configuration (Q931)
Q.931 Profile Selection
The Q.931 port can be profiled to conform to ETSI, AT&T (TR 41449), Euro-ISDN or QSIG
definitions. The default is QSIG. For DPNSS/QSIG transparency the profile must be set to QSIG.
The ETSI profile is based on ETSI Specification ETS 300 102-1, (ref. [B.18]). The
Euro-ISDN profile is based on the same specification, with amendments applied in ETSI
specification ETS 300 102-1/A2, (ref. [B.19]). The differences between the ETSI and
Euro-ISDN profiles relate to the content of messages; there are no changes to call set-up
and clear-down.
It is recommended that Euro-ISDN profile should be used when not configuring the
InterChange iQ 2000 for transparency, irrespective of a requirement for TBR-4 compliancy.
Choose the ETSI profile only where TBR-4 compliancy is not required and where it is
deemed the Euro-ISDN profile to be incorrect. Where TBR-4 compliance is required, the
Euro-ISDN profile must be chosen.
Each profile sets particular defaults, appropriate to the standard definition, but these values can
then be overridden by specific action, allowing customisation of the interface to non-standard
equipment implementations. The rest of this section discusses these override options.
Protocol Orientation
The default Layer 3 configuration sets all Q.931 channels to
USER
orientation. This
orientation can be altered to
NETWORK
.
Action on Link Layer RESET
As default, the Interchange iQ 2000 takes action to validate Q.931 call status for all fully
active calls on notification of a Link Layer RESET. Calls are only cleared if not fully set up or
there is a discrepancy in call state.
This can be reconfigured, to cause all calls to be cleared when a Layer 2 fault is
notified, regardless of their state. If the glitch sensitivity has been reduced in Channel 0
configuration, it may be appropriate to clear calls once a fault is finally notified. Status
validation should be adequate in most cases.
