Need kind help in Implementation of priority queue

Can anyone help me in finding the implementation of sendsms in SMSBOX i mean if 
i have following URL:

     
"http://localhost:13013/cgi-bin/sendsms?username=tester&password=foobar&text=hello&priority=3&to=+123456789";


then i want to know how kannel deal with priority=3 in kannel. Its handling it 
in smsbox.c file or in bearerbox.c file. This URL will tell tell smsbox about 
the priority or its telling bearerbox about this priority. In both cases how 
kannel handles it in code. 


Adil Nazir