diff --git a/sim/core.h b/sim/core.h
new file mode 100644
index 0000000..7db554b
--- /dev/null
+++ b/sim/core.h
@@ -0,0 +1,63 @@
+/*
+    Copyright (C) 2018 Open Networking Foundation
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef OPENOLT_CORE_H_
+#define OPENOLT_CORE_H_
+
+#include <grpc++/grpc++.h>
+using grpc::Status;
+#include <openolt.grpc.pb.h>
+#include "Queue.h"
+
+extern Queue<openolt::Indication> oltIndQ;
+
+Status Enable_(int argc, char *argv[]);
+Status ActivateOnu_(uint32_t intf_id, uint32_t onu_id,
+    const char *vendor_id, const char *vendor_specific, uint32_t pir);
+Status DeactivateOnu_(uint32_t intf_id, uint32_t onu_id,
+    const char *vendor_id, const char *vendor_specific);
+Status DeleteOnu_(uint32_t intf_id, uint32_t onu_id,
+    const char *vendor_id, const char *vendor_specific);
+Status EnablePonIf_(uint32_t intf_id);
+Status DisablePonIf_(uint32_t intf_id);
+Status EnableUplinkIf_(uint32_t intf_id);
+Status DisableUplinkIf_(uint32_t intf_id);
+Status OmciMsgOut_(uint32_t intf_id, uint32_t onu_id, const std::string pkt);
+Status OnuPacketOut_(uint32_t intf_id, uint32_t onu_id, const std::string pkt);
+Status UplinkPacketOut_(uint32_t intf_id, const std::string pkt);
+Status FlowAdd_(uint32_t onu_id,
+                uint32_t flow_id, const std::string flow_type,
+                uint32_t access_intf_id, uint32_t network_intf_id,
+                uint32_t gemport_id, uint32_t priority,
+                const ::openolt::Classifier& classifier,
+                const ::openolt::Action& action);
+Status Disable_();
+Status Reenable_();
+
+
+static Status SchedAdd_(int intf_id, int onu_id, int agg_port_id);
+static Status SchedRemove_(int intf_id, int onu_id, int agg_port_id);
+
+static inline int mk_sched_id(int onu_id) {
+    return 1023 + onu_id;
+}
+
+static inline int mk_agg_port_id(int onu_id) {
+    return 1023 + onu_id;
+}
+
+#endif