code: protected void register(MobicentsSipServletRequest request, MobicentsSipServletResponse response, SipPrincipal principal,
              String authType, String username, String password) {
  
          if (log.isDebugEnabled()) {
              // Bugzilla 39255: http://issues.apache.org/bugzilla/show_bug.cgi?id=39255
              String name = (principal == null) ? "none" : principal.getName();
              log.debug("Authenticated '" + name + "' with type '" + authType + "'");
          }
          request.setUserPrincipal(principal);
          MobicentsSipSession session = request.getSipSession();
          if (session != null) {
              session.setUserPrincipal(principal);
          }
      }
docs: Register an authenticated Principal and authentication type in our request, in the current session (if there is one), and
  with our SingleSignOn valve, if there is one. Set the appropriate cookie to be returned.
  
  @param request The servlet request we are processing
  @param response The servlet response we are generating
  @param principal The authenticated Principal to be registered
  @param authType The authentication type to be registered
  @param username Username used to authenticate (if any)
  @param password Password used to authenticate (if any)