ict/perm_response_header is a SAP Parameter attribute which is used to control Send fixed header field with every response information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
With this parameter a single HTTP header field with a specified value
can be inserted into all HTTP responses of the AS ABAP server. The
syntax of the parameter is <(><<)>Name>:<(><<)>Value>
No empty spaces are allowed before or after a colon.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.