diff --git a/device/device_olt.go b/device/device_olt.go
index b3dc2c3..719f67b 100644
--- a/device/device_olt.go
+++ b/device/device_olt.go
@@ -21,13 +21,14 @@
 	"sync"
 )
 
-type DeviceState int
+//State represents the OLT States
+type State int
 
 // Device interface provides common methods for OLT and ONU devices
 type Device interface {
 	Initialize()
-	UpdateIntState(intstate DeviceState)
-	GetIntState() DeviceState
+	UpdateIntState(intstate State)
+	GetIntState() State
 	GetDevkey() Devkey
 }
 
@@ -46,10 +47,10 @@
 	SerialNumber       string
 	Manufacture        string
 	Name               string
-	InternalState      DeviceState
+	InternalState      State
 	OperState          string
-	NniIntfs           []nniIntf
-	PonIntfs           []ponIntf
+	NniIntfs           []Port
+	PonIntfs           []Port
 	HeartbeatSignature uint32
 	mu                 *sync.Mutex
 }
@@ -68,21 +69,21 @@
 	NniLosRaised
 )
 
-type ponIntf struct {
+// Port info for NNI and PON ports
+type Port struct {
 	Type       string
 	IntfID     uint32
 	OperState  string
 	AlarmState AlarmState
+	PortStats  PortStats
 }
 
-type nniIntf struct {
-	Type       string
-	IntfID     uint32
-	OperState  string
-	AlarmState AlarmState
+// PortStats for NNI and PON ports
+type PortStats struct {
+	Packets uint64
 }
 
-// Constants for port types
+// Constants for Port types
 const (
 	IntfPon = "pon"
 	IntfNni = "nni"
@@ -96,9 +97,9 @@
 
 // Constants for OLT states
 const (
-	OLT_INACTIVE  DeviceState = iota // OLT/ONUs are not instantiated
-	OLT_PREACTIVE                    // Before PacketInDaemon Running
-	OLT_ACTIVE                       // After PacketInDaemon Running
+	OltInactive  State = iota // OLT/ONUs are not instantiated
+	OltPreactive              // Before PacketInDaemon Running
+	OltActive                 // After PacketInDaemon Running
 )
 
 // OLTAlarmStateToString is used to get alarm state as string
@@ -116,12 +117,12 @@
 	olt.NumPonIntf = npon
 	olt.NumNniIntf = nnni
 	olt.Name = "BBSIM OLT"
-	olt.InternalState = OLT_INACTIVE
+	olt.InternalState = OltInactive
 	olt.OperState = "up"
 	olt.Manufacture = "BBSIM"
 	olt.SerialNumber = "BBSIMOLT00" + strconv.FormatInt(int64(oltid), 10)
-	olt.NniIntfs = make([]nniIntf, olt.NumNniIntf)
-	olt.PonIntfs = make([]ponIntf, olt.NumPonIntf)
+	olt.NniIntfs = make([]Port, olt.NumNniIntf)
+	olt.PonIntfs = make([]Port, olt.NumPonIntf)
 	olt.HeartbeatSignature = oltid
 	olt.mu = &sync.Mutex{}
 	for i := uint32(0); i < olt.NumNniIntf; i++ {
@@ -141,7 +142,7 @@
 
 // Initialize method initializes NNI and PON ports
 func (olt *Olt) Initialize() {
-	olt.InternalState = OLT_INACTIVE
+	olt.InternalState = OltInactive
 	olt.OperState = "up"
 	for i := uint32(0); i < olt.NumNniIntf; i++ {
 		olt.NniIntfs[i].IntfID = i
@@ -158,7 +159,7 @@
 }
 
 // GetIntState returns internal state of OLT
-func (olt *Olt) GetIntState() DeviceState {
+func (olt *Olt) GetIntState() State {
 	olt.mu.Lock()
 	defer olt.mu.Unlock()
 	return olt.InternalState
@@ -170,7 +171,7 @@
 }
 
 // UpdateIntState method updates OLT internal state
-func (olt *Olt) UpdateIntState(intstate DeviceState) {
+func (olt *Olt) UpdateIntState(intstate State) {
 	olt.mu.Lock()
 	defer olt.mu.Unlock()
 	olt.InternalState = intstate
diff --git a/device/device_onu.go b/device/device_onu.go
index aafa793..b0af2c2 100644
--- a/device/device_onu.go
+++ b/device/device_onu.go
@@ -22,43 +22,51 @@
 
 	"github.com/opencord/voltha-bbsim/common/logger"
 	openolt "github.com/opencord/voltha-protos/go/openolt"
+	techprofile "github.com/opencord/voltha-protos/go/tech_profile"
 	log "github.com/sirupsen/logrus"
 )
 
 // Constants for the ONU states
 const (
-	ONU_INACTIVE DeviceState = iota // TODO: Each stage name should be more accurate
-	ONU_ACTIVE
-	ONU_OMCIACTIVE
-	ONU_AUTHENTICATED
-	ONU_LOS_RAISED
-	ONU_OMCI_CHANNEL_LOS_RAISED
-	ONU_LOS_ON_OLT_PON_LOS // TODO give more suitable and crisp name
-	ONU_FREE
+	OnuFree State = iota // TODO: Each stage name should be more accurate
+	OnuInactive
+	OnuLosRaised
+	OnuLosOnOltPonLos
+	OnuOmciChannelLosRaised
+	OnuActive
+	OnuOmciActive
+	OnuAuthenticated
 )
 
 // ONUState maps int value of device state to string
-var ONUState = map[DeviceState]string{
-	ONU_INACTIVE:                "ONU_INACTIVE",
-	ONU_ACTIVE:                  "ONU_ACTIVE",
-	ONU_OMCIACTIVE:              "ONU_OMCIACTIVE",
-	ONU_AUTHENTICATED:           "ONU_AUTHENTICATED",
-	ONU_LOS_RAISED:              "ONU_LOS_RAISED",
-	ONU_OMCI_CHANNEL_LOS_RAISED: "ONU_OMCI_CHANNEL_LOS_RAISED",
-	ONU_LOS_ON_OLT_PON_LOS:      "ONU_LOS_ON_OLT_PON_LOS",
-	ONU_FREE:                    "ONU_FREE",
+var ONUState = map[State]string{
+	OnuFree:                 "ONU_FREE",
+	OnuInactive:             "ONU_INACTIVE",
+	OnuLosRaised:            "ONU_LOS_RAISED",
+	OnuLosOnOltPonLos:       "ONU_LOS_ON_OLT_PON_LOS",
+	OnuOmciChannelLosRaised: "ONU_OMCI_CHANNEL_LOS_RAISED",
+	OnuActive:               "ONU_ACTIVE",
+	OnuOmciActive:           "ONU_OMCIACTIVE",
+	OnuAuthenticated:        "ONU_AUTHENTICATED",
+}
+
+// FlowKey used for FlowMap key
+type FlowKey struct {
+	FlowID        uint32
+	FlowDirection string
 }
 
 // Onu structure stores information of ONUs
 type Onu struct {
-	InternalState DeviceState
+	InternalState State
 	OltID         uint32
 	IntfID        uint32
 	OperState     string
 	SerialNumber  *openolt.SerialNumber
 	OnuID         uint32
-	GemportID     uint16
-	FlowIDs       []uint32
+	GemPortMap    map[uint32][]uint32 // alloc-id is used as key and corresponding gem-ports are stored in slice
+	Tconts        *techprofile.TrafficSchedulers
+	Flows         []FlowKey
 	mu            *sync.Mutex
 }
 
@@ -69,11 +77,11 @@
 }
 
 // NewOnus initializes and returns slice of Onu objects
-func NewOnus(oltid uint32, intfid uint32, nonus uint32, nnni uint32) []*Onu {
-	onus := []*Onu{}
+func NewOnus(oltid uint32, intfid uint32, nonus uint32) []*Onu {
+	var onus []*Onu
 	for i := 1; i <= int(nonus); i++ {
 		onu := Onu{}
-		onu.InternalState = ONU_FREE // New Onu Initialised with state ONU_FREE
+		onu.InternalState = OnuFree // New Onu Initialised with state ONU_FREE
 		onu.mu = &sync.Mutex{}
 		onu.IntfID = intfid
 		onu.OltID = oltid
@@ -81,7 +89,7 @@
 		onu.SerialNumber = new(openolt.SerialNumber)
 		onu.SerialNumber.VendorId = []byte("BBSM")
 		onu.SerialNumber.VendorSpecific = NewSN(oltid, intfid, uint32(i))
-		onu.GemportID = 0
+		onu.GemPortMap = make(map[uint32][]uint32)
 		onus = append(onus, &onu)
 	}
 	return onus
@@ -90,19 +98,7 @@
 // Initialize method initializes ONU state to up and ONU_INACTIVE
 func (onu *Onu) Initialize() {
 	onu.OperState = "up"
-	onu.InternalState = ONU_INACTIVE
-}
-
-// ValidateONU method validate ONU based on the serial number in onuMap
-func ValidateONU(targetonu openolt.Onu, regonus map[uint32][]*Onu) bool {
-	for _, onus := range regonus {
-		for _, onu := range onus {
-			if ValidateSN(*targetonu.SerialNumber, *onu.SerialNumber) {
-				return true
-			}
-		}
-	}
-	return false
+	onu.InternalState = OnuInactive
 }
 
 // ValidateSN compares two serial numbers and returns result as true/false
@@ -120,7 +116,7 @@
 }
 
 // UpdateIntState method updates ONU internal state
-func (onu *Onu) UpdateIntState(intstate DeviceState) {
+func (onu *Onu) UpdateIntState(intstate State) {
 	onu.mu.Lock()
 	defer onu.mu.Unlock()
 	onu.InternalState = intstate
@@ -132,21 +128,21 @@
 }
 
 // GetIntState returns ONU internal state
-func (onu *Onu) GetIntState() DeviceState {
+func (onu *Onu) GetIntState() State {
 	onu.mu.Lock()
 	defer onu.mu.Unlock()
 	return onu.InternalState
 }
 
-// DeleteFlowID method search and delete flowID from the onu flowIDs slice
-func (onu *Onu) DeleteFlowID(flowID uint32) {
-	for pos, id := range onu.FlowIDs {
-		if id == flowID {
-			// delete the flowID by shifting all flowIDs by one
-			onu.FlowIDs = append(onu.FlowIDs[:pos], onu.FlowIDs[pos+1:]...)
-			t := make([]uint32, len(onu.FlowIDs))
-			copy(t, onu.FlowIDs)
-			onu.FlowIDs = t
+// DeleteFlow method search and delete flowKey from the onu flows slice
+func (onu *Onu) DeleteFlow(key FlowKey) {
+	for pos, flowKey := range onu.Flows {
+		if flowKey == key {
+			// delete the flowKey by shifting all flowKeys by one
+			onu.Flows = append(onu.Flows[:pos], onu.Flows[pos+1:]...)
+			t := make([]FlowKey, len(onu.Flows))
+			copy(t, onu.Flows)
+			onu.Flows = t
 			break
 		}
 	}
diff --git a/device/utils.go b/device/utils.go
index 7e0eca3..2d4cc28 100644
--- a/device/utils.go
+++ b/device/utils.go
@@ -17,19 +17,17 @@
 package device
 
 import (
-	"fmt"
-
 	"github.com/opencord/voltha-bbsim/common/logger"
 	log "github.com/sirupsen/logrus"
 	"strconv"
 )
 
+// OnuToSn returns serial number in string format for given ONU
 func OnuToSn(onu *Onu) string {
-	// FIXME
-	// see https://github.com/opencord/voltha/blob/master/voltha/adapters/openolt/openolt_device.py#L929-L943
-	return string(onu.SerialNumber.VendorId) + "00000" + fmt.Sprint(onu.IntfID) + "0" + fmt.Sprintf("%x", onu.OnuID-1)
+	return string(onu.SerialNumber.VendorId) + ConvB2S(onu.SerialNumber.VendorSpecific)
 }
 
+// LoggerWithOnu method logs ONU fields
 func LoggerWithOnu(onu *Onu) *log.Entry {
 
 	if onu == nil {
@@ -39,12 +37,13 @@
 
 	return logger.GetLogger().WithFields(log.Fields{
 		"serial_number": OnuToSn(onu),
-		"interfaceId":   onu.IntfID,
-		"onuId":         onu.OnuID,
-		"oltId":         onu.OltID,
+		"interfaceID":   onu.IntfID,
+		"onuID":         onu.OnuID,
+		"oltID":         onu.OltID,
 	})
 }
 
+// ConvB2S converts byte array to string
 func ConvB2S(b []byte) string {
 	s := ""
 	for _, i := range b {