diff --git a/include/transport/protocol.proto b/include/transport/protocol.proto
index 8370e617..336915a0 100644
--- a/include/transport/protocol.proto
+++ b/include/transport/protocol.proto
@@ -1,5 +1,25 @@
 package pbnetwork;
 
+enum ConnectionError {
+	CONNECTION_ERROR_NETWORK_ERROR = 0;
+	CONNECTION_ERROR_INVALID_USERNAME = 1;
+	CONNECTION_ERROR_AUTHENTICATION_FAILED = 2;
+	CONNECTION_ERROR_AUTHENTICATION_IMPOSSIBLE = 3;
+	CONNECTION_ERROR_NO_SSL_SUPPORT = 4;
+	CONNECTION_ERROR_ENCRYPTION_ERROR = 5;
+	CONNECTION_ERROR_NAME_IN_USE = 6;
+	CONNECTION_ERROR_INVALID_SETTINGS = 7;
+	CONNECTION_ERROR_CERT_NOT_PROVIDED = 8;
+	CONNECTION_ERROR_CERT_UNTRUSTED = 9;
+	CONNECTION_ERROR_CERT_EXPIRED = 10;
+	CONNECTION_ERROR_CERT_NOT_ACTIVATED = 11;
+	CONNECTION_ERROR_CERT_HOSTNAME_MISMATCH = 12;
+	CONNECTION_ERROR_CERT_FINGERPRINT_MISMATCH = 13;
+	CONNECTION_ERROR_CERT_SELF_SIGNED = 14;
+	CONNECTION_ERROR_CERT_OTHER_ERROR = 15;
+	CONNECTION_ERROR_OTHER_ERROR = 16;
+}
+
 enum StatusType {
 	STATUS_ONLINE		= 0;
 	STATUS_AWAY			= 1;
@@ -135,4 +155,4 @@ message WrapperMessage {
 	required Type type = 1;
 	optional bytes payload = 2;
 }
-;
\ No newline at end of file
+;