396 NT6D80 MSDL cardThe MSDL uses the MSDL receive interface to communicate with thesystem. The MSDL card receives packetized data from the I/O equipmentover the MSDL ports. This data is processed by the MSDL handler and sentto the appropriate function.The flow control mechanism provides an orderly exchange of transmitand receive messages for each operation. Each operation has a numberof outstanding messages stored in buffers waiting to be sent to theirdestinations. As long as the number of messages does not exceed thethreshold specified, the messages queue in the buffer in a first-in-first-outprocess.If the outstanding number of messages for an operation reaches thethreshold, the flow control mechanism informs the sender to wait untilthe number of messages is below the threshold before sending the nextmessage.If buffer space is not available, the request to send a message to the bufferis rejected and a NO BUFFER fault indication is sent.Engineering guidelinesAvailable network card slotsThe number of available network slots depends on the system option, thesystem size, and the number of available network slots in each module forthe selected system option.Some of these network card slots are normally occupied by Network cards,Superloop Network cards, Conference/TDS, and others, leaving a limitednumber of unused slots for MSDL and other cards.Card mixA system that exclusively uses MSDL cards can support up to 16 suchcards, providing 64 ports. These ports can be used to run varioussynchronous and asynchronous operations simultaneously.The system also supports a mix of interface cards (MSDL, DCHI, and ESDIfor example). However, using multiple card types reduce the number ofcards and ports available.Address decodingThe MSDL card decodes the full address information received fromthe system. This provides 128 unique addresses. Since MSDL portscommunicate with the CPU using a single card address, the system cansupport 16 MSDL cards providing 64 ports.Nortel Communication Server 1000Circuit Card ReferenceNN43001-311 01.04 StandardRelease 5.0 23 May 2008Copyright © 2003-2008, Nortel Networks.
