diff --git a/core/constants/network.go b/core/constants/network.go
new file mode 100644
index 0000000..b0f5355
--- /dev/null
+++ b/core/constants/network.go
@@ -0,0 +1,52 @@
+package constants
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+type PortType int
+
+const (
+	PortTypeTCP PortType = iota
+	PortTypeUDP
+)
+
+var (
+	portTypeID = map[PortType]string{
+		PortTypeTCP: "TCP",
+		PortTypeUDP: "UDP",
+	}
+
+	portTypeName = map[string]PortType{
+		"TCP": PortTypeTCP,
+		"UDP": PortTypeUDP,
+	}
+)
+
+func (pt PortType) String() string {
+	return portTypeID[pt]
+}
+
+func (pt PortType) MarshalJSON() ([]byte, error) {
+	value, ok := portTypeID[pt]
+	if !ok {
+		return nil, fmt.Errorf("Invalid EnumType[%s] value", pt)
+	}
+	return json.Marshal(value)
+}
+
+func (pt PortType) UnmarshalJSON(b []byte) error {
+	var s string
+	err := json.Unmarshal(b, &s)
+	if err != nil {
+		return err
+	}
+
+	value, ok := portTypeName[s]
+	if !ok {
+		return fmt.Errorf("Invalid EnumType[%s] value", s)
+	}
+	pt = value
+	return nil
+}