Nortel Networks Circuit Card User Manual

 NTBK22 MISP card

Refer to ISDN Basic Rate Interface: Installation and Configuration 
(553-3001-218) and ISDN Basic Rate Interface: Features (553-3001-380) for 
additional information.

Each MISP can support 4 line cards (UILC or SILC or any combination of the 
two). Each line card supports 8 DSLs, therefore each MISP supports 32 
DSLs. Since each DSL uses two B-channels and one D-channel the MISP 
supports 64 B-channels and 32 D-channels. If the MISP is carrying packet 
data, it must dedicate one of its D-channels to communicate with the external 
packet handler. In this case the MISP supports only 31 DSLs.

The main functions of the MISP are:

•

communicate with the Call Server CPU to report ISDN BRI status and 
receive downloaded application software and configuration parameters

•

manage Layer 2 and Layer 3 signaling that controls call connection and 
terminal identification

•

control terminal initialization and addressing

•

assign B-channels for switched voice and data transmission by 
communicating with the BRI terminal over the D-channel and allocating 
to it an idle B-channel with appropriate bearer capabilities

•

separate D-channel data from signaling information and route the data to 
the packet handler

•

send call control messages to ISDN BRI terminals over the D-channel

The MPU coordinates and controls data transfer and addressing of the 
peripheral devices and communicates with the CPU using a message channel 
on the CPU bus. The tasks that the MPU performs depend on the interrupts it 
receives. The interrupts are prioritized by the importance of the tasks they 
control.