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V.24 / X.21
LAM
DNR
CV
Figure 2-7 Gateway to Data Network.
The ISPBX data party dials (as for an internal data calls) the DNR of the LAM circuit which is
connected to the gateway server. The gateway server answers the call. Now a transparent
connection is established between this data party and the gateway server. The data party then
selects the destination data party using, for instance, post dialling. The gateway server takes
care of the connection through the data network. The gateway server now performs the
conversion between the two interface types. The ISPBX data party can now communicate
with the external data party, via the gateway server, using a protocol that is not supported by
the ISPBX itself.
The LAMs which are connected to the gateway server can be assigned to a group arrangement
with group hunting. In this case, the data party does not have to dial a free LAM-gateway but
only the group DNR. Group hunting ensures that a free LAM-gateway circuit is accessed.
2.6.
BASIC SERVICE PROFILES (BSP)
A Basic Service Profile is the combination of a DNR and a Basic Service Profile Type (BSPT)
and is identified by a Basic Service Profile - Identifier (BSP-ID). This BSP-ID is assigned to a line
circuit by OM: CHDNRC
One extension circuit (EHWA) can have several BSP-IDs assigned. These BSP-IDs may have
different DNRs and different BSPTs.
A call to this circuit will be checked for compatibility. If the destination DNR and the IBSC of
the caller match with more than one BSP-ID, the BSP-ID with the lowest numbered BSPT is
selected.
A call, set up by a non-ISDN extension, will always use the BSP-ID with the lowest numbered
BSPT. An ISDN extension, however, can differentiate between BSP-IDs.
2B+D
IMP
64 kbps
64 kbps
DLC
SN
IMP
2B+D
64 kbps
64 kbps
DLC
Other interface types
e.g. X.25
V.24 / X.21
LAM
DNR
CV
GATEWAY
SERVER
Data
network
23
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