code: public void setParameterableHeader(String name, Parameterable param) {
  		if(logger.isDebugEnabled()) {
          	logger.debug("setParameterableHeader - name=" + name + ", param=" + param);
          }
  
  		checkCommitted();
  		if(isSystemHeader(getModifiableRule(name))) {
  			throw new IllegalArgumentException(name + " is a system header !");
  		}
  		try {
  			this.message.setHeader(SipFactoryImpl.headerFactory.createHeader(name, param.toString()));
  		} catch (ParseException e) {
  			throw new IllegalArgumentException("Impossible to set this parameterable header", e);
  		}
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipServletMessage#setParameterableHeader(java.lang.String, javax.servlet.sip.Parameterable)