diff --git a/dns.rcodes.js b/dns.rcodes.js
new file mode 100644
index 0000000..e1a3c0f
--- /dev/null
+++ b/dns.rcodes.js
@@ -0,0 +1,15 @@
+(function (exports) {
+'use strict';
+
+var rcodes = exports.DNS_RCODES = {
+  SUCCESS:  0x00  //   0
+, NXDOMAIN: 0x03  //   3
+, REFUSED:  0x05  //   5
+};
+
+// and in reverse
+Object.keys(rcodes).forEach(function (key) {
+  rcodes[rcodes[key]] = key;
+});
+
+}('undefined' !== typeof window ? window : exports));