Isdn Bri Circuit-Switched Data Calls - Nortel Meridian 1 Administration And Maintenance

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Chapter 2 — Feature descriptions

ISDN BRI circuit-switched data calls

553-3011-311 Standard 7.0
ISDN BRI to ISDN BRI circuit-switched data calls
Circuit-switched data calls between two ISDN BRI terminals are supported
for all bearer capability encodings. The Meridian 1 screens for the validity of
its bearer capability codepoints only; it does not screen for protocol
compatibility between two ISDN BRI devices. The Meridian 1 presents the
call to the terminating party; the two ISDN BRI devices determine whether
they can communicate with the specified bearer capability. If the ISDN BRI
terminals decide that the protocol is incompatible, either terminal may drop
the call.
ISDN BRI accessing Meridian 1 data modules
Meridian 1 offers data access through special data adapters (for example,
ASIM). These adapters provide Northern Telecom proprietary DM-DM
protocol for data transmission. The ISDN BRI terminal cannot communicate
with these adapters because of protocol incompatibility. Calls from an ISDN
BRI terminal to these data modules are blocked; similarly, calls from these
data modules to an ISDN BRI terminal are also blocked.
ISDN BRI terminals can communicate with these data modules under one
condition: ISDN BRI terminals that support the TLINK protocol can
communicate with these Meridian 1 data adapters if the circuit-switched data
call is placed across an ISDN PRI or DTI link. This access is possible because
the ISDN PRI or DTI pack provides protocol conversion from TLINK to
DM-DM and vice versa.
ISDN BRI accessing Meridian Communication Adapters
The MCA operates in three modes: DM-DM, TLINK and PSDS. An MCA
operating in TLINK mode communicates with ISDN BRI terminals that
support TLINK protocol. Calls from an ISDN BRI terminal (with the
appropriate bearer capability encodings) to an MCA and vice versa are
allowed to terminate; however, if the protocol exchange fails between the
ISDN BRI and MCA devices, if the MCA is not operating in TLINK mode,
for example, then the call may be dropped by either device.
May 1999