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2.0 Mb DTI/PRI Administration and Maintenance Guide Book ... - Home

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Page 796 of 1536 Chapter 3 — DPNSS1/DASS2 features description <strong>and</strong> implementation<br />

DPNSS1 network at the originating node, at a transit node, at an<br />

ISDN-to-DPNSS1 gateway, <strong>and</strong> at a DPNSS1-to-ISDN gateway.<br />

DPNSS1-to-ISDN gateway node operation<br />

Node A DPNSS1 Node B ISDN Node C<br />

An attempt is being made to establish a call through an<br />

DPNSS1-to-ISDN gateway, from originating node A to terminating node<br />

C, via gateway node B. In order to provide a consistent interworking<br />

between ISDN Drop Back Busy <strong>and</strong> DPNSS1 Step Back on Congestion,<br />

the options for IDBB <strong>and</strong> OHQ are included at gateway node B in the<br />

SETUP message from the outgoing route list block. If all the trunks at<br />

node C are busy, <strong>and</strong> drop back occurs, a DISCONNECT message with<br />

a cause of normal clear is sent to gateway node B, where it is recognized<br />

as a drop back attempt. The DISCONNECT message is mapped to a<br />

CRM with a reason of congestion, so that Step Back on Congestion is<br />

invoked in the DPNSS1 segment of the path.<br />

— DPNSS1 operation will not support the following:<br />

• ISDN Basic Rate Interface (BRI) sets<br />

or<br />

• ISDN BRI Numeris Terminals.<br />

553-3011-315 St<strong>and</strong>ard 10.0 May 1999<br />

ISRM SETUP (idbb, ohq)<br />

CRM (congestion)<br />

All<br />

other<br />

routes<br />

553-7995.EPS

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