Example: link-by-link
routing
Exchange
Exchange
Exchange
SPC = 82
Circuit 14
SPC = 22
SPC = 60
Circuit 20
SPC = 18
SPC = 15
STP
SL 4
Outgoing MTP
MSU:
OPC = 22 CIC = 20
DPC = 60 SLS = 2
SL 2
SL 7
STP
Outgoing
message:
OPC = 82 CIC = 14
DPC = 22 SLS = 4
Processing in
(transit) exchange(s):
Received message is sent to
user (ISUP) that gives B-number to exchange. Exchange performs number analysis and selects new DPC (60)
and CIC (20) 
Using MTP-level
routing table, STP routes message to DPC = 22
