Nortel Meridian Meridian 1 Feature Description And Administration page 1191

Note: To ensure that MCDN Alternate Routing occurs for all nodes in a
system, define all nodes as SBOC = RRA. Conversely, to prevent
MCDN Alternate Routing from occurring on any nodes, define all nodes
as SBOC = NRR.
Refer to "Originating node operation" on page 1191, "Transit node
operation" on page 1193, and "MCDN Alternate Routing examples" on
page 1195 for more information on MCDN Alternate Routing operation for
each SBOC prompt.
Note: If any of the cause values listed below are received in a Call
Clearing message, the non-MCDN Alternate Routing retry operation
occurs. That is, an attempt is made to retry the call. The retry first
attempts to find another idle channel in the same route. If all the channels
in that route are busy, it attempts to find another channel in the next
alternate route in the Route List Block.
• Cause 6 = Channel unacceptable
• Cause 44 = Requested circuit/channel not available
• Cause 82 = Identified channel does not exist
Refer to Figure 94, Originating node operation. If Node C sends one of
the non-MCDN Alternate Routing cause values, the Call Clearing
message is sent back to Node A which attempts non-MCDN Alternate
Routing.
Refer to Figure 95, Transit node operation. If Node C receives one of the
non-MCDN Alternate Routing cause values:
• Node C attempts to find an alternate route but none is available.
• Node B is a transit note and does not attempt to find an alternate route.
• Node A attempts to find an alternate route but none is available.
Originating node operation
Consider the following calling scenario for an originating node operation. An
attempt is being made to establish a call over an MCDN link, from originating
node A to terminating node D, through transit nodes B and C. Congestion
occurs between nodes C and D.
MCDN Alternate Routing
International ISDN PRI Feature description and administration
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