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Distributed Communications System B Private Networking
Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000
320
ISDN/X.25 gateway
DEFINITY ECS can serve as an interface between PBXs that support the D-channel
signaling feature and those that do not support this feature. The switch providing this
interface is known as the ISDN-DCS Gateway node and provides backward
compatibility to existing traditional DCS networks.
It maintains a mapping between processor channels and Administered NCA-TSCs.
When a DCS D-channel message arrives on an Administered NCA-TSC acting as a
gateway, it is converted to a traditional DCS message and sent out through the
processor channel that has been administered to map to this Administered NCA-TSC.
Likewise, when a traditional DCS message arrives at the gateway node on a processor
channel acting as a gateway, it is converted to a DCS D-channel message and sent out
through the Administered NCA-TSC that has been associated with this processor
channel on the ISDN Gateway Channel form.
In summary, a gateway is required whenever a transition is being made from BX.25
signaling to D-channel signaling. When the transition takes place at a switch that sits
between that part of the network that supports D-channel DCS and that part that does
not, that switch is an ISDN-DCS Gateway. A DCS network consisting entirely of
switches that support D-channel DCS never requires an ISDN-DCS Gateway because
none of the switches require “translation” to/from BX.25.
DCS Over ISDN-PRI D-channel
DCS Over ISDN-PRI D-channel (DCS+) enhances DCS by allowing access to the
public network for DCS connectivity between DCS switch nodes. With this feature,
DCS features are no longer restricted to private facilities.
The ISDN-PRI B-channel is used for voice communications, and the ISDN-PRI
D-channel transports DCS control information. DCS Over ISDN-PRI utilizes the
Message-Associated User-to-User Information (MA-UUI) and Temporary Signaling
Connections (TSC) to transport certain DCS control information. MA-UUI allows
additional user-specific information to be transported along with certain ISDN
call-control messages.
Note: Use this feature only over DS1/E1 or T1 circuit packs that are
administered to Country Protocol Option 1, Protocol Version A
(even in a private network environment) independent of what
country the system is in.