Please i need to know the file (directory,dialplan or ........) from which the request register is send ,I need your help ,

i need to know the origine of the message Register to be able to modify it i need to create a scenario which is:

FS receive Register

FS send 401 

FS receive  Register with authorization header

FS send second 401 with stale = false 

please i need your help .

thank you again 

with best regards 

amani