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Distributed Communications System
B Private Networking
NCA-TSC
An NCA-TSC is a connection not related with any ISDN B-channel connections.
DECINITY ECS supports two types of NCA-TSC that conform to two different
protocol standards:
• The QSIG type of NCA-TSC is used for certain QSIG features such as Call
Completion (Automatic Call Back). This type of NCA-TSC is referred to in the
QSIG protocol standards as a Call-Independent Signaling Connection (CISC).
Only ISDN-PRI Signaling Groups administered with Supplementary Service
Protocol b support QSIG NCA-TSCs. For further information, see NCA-TSC
(page 370).
• The AT&T type of NCA-TSC is used for the DCS Over ISDN-PRI D-channel and
DCS AUDIX applications. Only ISDN-PRI Signaling Groups administered with
Supplementary Service Protocol a support AT&T NCA-TSCs.
An AT&T NCA-TSC is an administered virtual connection established for
exchanging USER INFORMATION messages on the ISDN D-channel. Once an
AT&T NCA-TSC has been administered and enabled, it is active for an extended
period of time. There are two types of administered NCA-TSCs depending on
their setup mechanism:
~ Permanent (can be established by Near-end or Far-end)
~ As-needed
Once enabled, a permanent NCA-TSC remains established while the system is
running. If the permanent NCA-TSC drops for any reason, the system attempts to
reestablish the connection. An as-needed administered NCA-TSC is established
based on user request and the availability of TSC facilities. The connection drops
after an administered period of inactivity.
The system can transport DCS or DCS AUDIX messages over an ISDN-PRI
D-channel and over BX.25 data links when functioning as a gateway between a
switch equipped with DCS Over ISDN-PRI D-channel and a switch equipped with
traditional DCS using BX.25 data links. In this situation, the messages travel from
the gateway through the NCA-TSCs or CA-TSCs to TSC-capable switches and
from the gateway to switches that support only traditional DCS via a BX.25
logical channel.
At least one switch must be configured as an ISDN DCS Gateway node in a DCS
network that consists of switches that support DCS Over ISDN-PRI D-channel
and PBXs that do not support the feature. Switches directly connected to AUDIX
serve as Gateway nodes.
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Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000