code: public void sendReliably() throws Rel100Exception {
  		final int statusCode = getStatus();
  		if(statusCode == 100 || statusCode >= 200) {
  			throw new Rel100Exception(Rel100Exception.NOT_1XX);
  		}
  		if(!Request.INVITE.equals(originalRequest.getMethod())) {
  			throw new Rel100Exception(Rel100Exception.NOT_INVITE);
  		}		
  		if(!containsRel100(originalRequest.getMessage())) {
  			throw new Rel100Exception(Rel100Exception.NO_REQ_SUPPORT);
  		}
  		try {
  			send(true);
  		} catch (IOException e) {
  			// sendReliably doesn't throw IOException where send() does...
  			throw new IllegalStateException(e);
  		}
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipServletResponse#sendReliably()