This is a special non-standard feature of YATE.
The SCCP can be used as a SCCP message decoder. This case can be found if SCCP is used with M3UA-GW.
YATE M3UA-GW has the ability to route messages to ASPs based on SCCP GT or/and SSN, in this way the SCCP is used to decode the SCCP message for M3UA-GW so that the gateway can look for the routing parameters.
To activate this feature set in ysigchan.conf
[sccp] type=ss7-sccp pointcodetype=ITU localpointcode=7 priority=0 decoder=true