diff --git a/srt/data_chain.go b/srt/data_chain.go
index d1a34d7..9576b73 100644
--- a/srt/data_chain.go
+++ b/srt/data_chain.go
@@ -3,6 +3,7 @@ package srt
 import (
 	"math"
 	"sort"
+	"io"
 )
 
 type Datum struct {
@@ -70,17 +71,57 @@ func NewDatumStorage(packet *Packet) (*DatumStorage) {
 	return storage
 }
 
+func (storage *DatumStorage) Expunge(output io.WriteCloser) (error) {
+	curr_datum := storage.main.root
+	seq_num_end := storage.main.end.seq_num
+	for curr_datum.seq_num != seq_num_end {
+		_, err := output.Write(curr_datum.data)
+		if err != nil {
+			return err
+		}
+		curr_datum = curr_datum.next
+	}
+	storage.main.root = curr_datum
+	return nil
+}
+
+func (buffer *DatumLink) InRange(new_seq_num uint32) (bool) {
+	start := buffer.root.seq_num
+	end := buffer.end.seq_num
+	if new_seq_num == start || new_seq_num == end {
+		return true
+	}
+	if !((start < new_seq_num && new_seq_num - start < (1 << 30)) || (start > new_seq_num && start - new_seq_num  > (1 << 30))) {
+		return false
+	}
+	if !((new_seq_num < end && end - new_seq_num < (1 << 30)) || (new_seq_num > end && new_seq_num - end > (1 << 30))) {
+		return false
+	}
+	return true
+}
+
 func (storage *DatumStorage) NewDatum(pkt *Packet) {
-	prev_num := (pkt.header_info.(*DataHeader).seq_num - 1) % uint32(math.Pow(2, 31))
+	new_pkt_num := pkt.header_info.(*DataHeader).seq_num
+	prev_num := (new_pkt_num - 1) % uint32(1 << 31)
 	if storage.main.end.seq_num == prev_num {
 		storage.main.NewDatum(pkt)
+	} else if storage.main.InRange(new_pkt_num) {
+		return
 	} else {
+		oldest := storage.main.root.seq_num
+		if (new_pkt_num < oldest && oldest - new_pkt_num < (1 << 30)) || (new_pkt_num > oldest && new_pkt_num - oldest > (1 << 30)) {
+			return
+		}
 		for _, v := range storage.offshoots {
 			if v.end.seq_num == prev_num {
 				v.NewDatum(pkt)
-				break
+				return
+			} else if v.InRange(new_pkt_num) {
+				return
 			}
 		}
+		new_link := NewDatumLink(pkt)
+		storage.offshoots = append(storage.offshoots, new_link)
 	}
 }
 
@@ -93,13 +134,31 @@ func (buffer *DatumLink) Link(buffer_next *DatumLink) {
 func check_append_serial_next(buffer *DatumLink, buffer_next *DatumLink) (bool) {
 	seq_1 := buffer.end.seq_num
 	seq_2 := (seq_1 + 1) % uint32(math.Pow(2, 31))
-	if seq_1 == seq_2 {
+	if buffer_next.root.seq_num == seq_2 {
 		buffer.Link(buffer_next)
 		return true
 	}
 	return false
 }
 
+func (storage *DatumStorage) GenNACKCIF() (*NACKCIF, bool) {
+	if len(storage.offshoots) == 0 {
+		return nil, false
+	}
+	cif := new(NACKCIF)
+	init_range := new(pckts_range)
+	init_range.start = (storage.main.end.seq_num + 1) % (1 << 31)
+	init_range.end = (storage.offshoots[0].root.seq_num - 1) % (1 << 31)
+	cif.lost_pkts = append(cif.lost_pkts, init_range)
+	for i := 0; i < len(storage.offshoots) - 1; i++ {
+		new_range := new(pckts_range)
+		new_range.start = (storage.offshoots[i].end.seq_num + 1) % (1 << 31)
+		new_range.end = (storage.offshoots[i + 1].root.seq_num - 1) % (1 << 31)
+		cif.lost_pkts = append(cif.lost_pkts, new_range)
+	}
+	return cif, true
+}
+
 func (storage *DatumStorage) Relink() {
 	sort.Sort(storage.offshoots)
 	buffer := storage.main
diff --git a/srt/intake.go b/srt/intake.go
index 6f81bbf..3cf7c0b 100644
--- a/srt/intake.go
+++ b/srt/intake.go
@@ -26,7 +26,7 @@ func (intake *Intake) NewTunnel(l net.PacketConn, peer net.Addr) (*Tunnel) {
 		tunnel := new(Tunnel)
 		tunnel.socket = l
 		tunnel.peer = peer
-		tunnel.queue = make(chan []byte, 100)
+		tunnel.queue = make(chan []byte, 10)
 		intake.tunnels = append(intake.tunnels, tunnel)
 		go tunnel.Start()
 		return tunnel
@@ -69,6 +69,6 @@ func (intake *Intake) Read() {
 	select {
 	case tunnel.queue <- pkt:
 	default:
-		tunnel.broken = true
+		//tunnel.broken = true
 	}
 }
diff --git a/srt/packet.go b/srt/packet.go
index a7d7e49..936a875 100644
--- a/srt/packet.go
+++ b/srt/packet.go
@@ -3,6 +3,7 @@ package srt
 import (
 	"errors"
 	"encoding/binary"
+	"fmt"
 )
 
 const (
@@ -109,7 +110,10 @@ func marshall_ctrl_packet(packet *Packet, header []byte) ([]byte, error) {
 	if !ok_head {
 		return header, errors.New("control packet does not have ctrl header")
 	}
-	header[0] = 0x80
+	binary.BigEndian.PutUint16(header[:2], ctrl_header.ctrl_type)
+	binary.BigEndian.PutUint16(header[2:4], ctrl_header.ctrl_subtype)
+	binary.BigEndian.PutUint32(header[4:8], ctrl_header.tsi)
+	header[0] |= 0x80
 	switch packet.packet_type {
 	case HANDSHAKE:
 		data, ok_data := packet.cif.(*HandshakeCIF)
@@ -119,22 +123,48 @@ func marshall_ctrl_packet(packet *Packet, header []byte) ([]byte, error) {
 		cif := marshall_hs_cif(data)
 		return append(header, cif...), nil
 	case SHUTDOWN:
-		header[1] |= 5
 		cif := make([]byte, 4)
 		return append(header, cif...), nil
 	case ACK:
-		header[1] |= 2
-		binary.BigEndian.PutUint32(header[4:8], ctrl_header.tsi)
 		data, ok_data := packet.cif.(*ACKCIF)
 		if !ok_data {
 			return header, errors.New("ACK has no data")
 		}
 		cif := marshall_ack_cif(data)
 		return append(header, cif...), nil
+	case NAK:
+		data, ok_data := packet.cif.(*NACKCIF)
+		if !ok_data {
+			return header, errors.New("NAK has no data")
+		}
+		cif := marshall_nack_cif(data)
+		return append(header, cif...), nil
 	}
 	return header, errors.New("Control packet type not recognized")
 }
 
+func marshall_nack_cif(data *NACKCIF) ([]byte) {
+	fmt.Println("new NAK")
+	var loss_list_bytes []byte
+	for _, pkts := range data.lost_pkts {
+		fmt.Println(pkts)
+		if pkts.start == pkts.end {
+			curr_bytes := make([]byte, 4)
+			binary.BigEndian.PutUint32(curr_bytes, pkts.start)
+			loss_list_bytes = append(loss_list_bytes, curr_bytes...)
+		} else {
+			curr_bytes := make([]byte, 8)
+			binary.BigEndian.PutUint32(curr_bytes[:4], pkts.start)
+			binary.BigEndian.PutUint32(curr_bytes[4:8], pkts.end)
+			if (pkts.end - pkts.start) % uint32(1 << 31) != 1 {
+				curr_bytes[0] |= 0x80
+			}
+			loss_list_bytes = append(loss_list_bytes, curr_bytes...)
+		}
+	}
+	return loss_list_bytes
+}
+
 func marshall_ack_cif(data *ACKCIF) ([]byte) {
 	cif := make([]byte, 28)
 	binary.BigEndian.PutUint32(cif[:4], data.last_acked)
diff --git a/srt/protocol.go b/srt/protocol.go
index 54e7c17..4522bda 100644
--- a/srt/protocol.go
+++ b/srt/protocol.go
@@ -25,6 +25,7 @@ type SRTManager struct {
 	storage *DatumStorage
 	ack_idx uint32
 	pings [][2]time.Time
+	last_nack time.Time
 	ping_offset int
 	pkt_sizes []uint32
 	bw uint32
@@ -220,6 +221,24 @@ func (agent *SRTManager) handle_ackack(packet *Packet) {
 	agent.pings[int(ack_num) - agent.ping_offset][1] = time.Now()
 }
 
+func (agent *SRTManager) create_nack_report() (*Packet) {
+	agent.last_nack = time.Now()
+	cif, ok := agent.storage.GenNACKCIF()
+	if !ok {
+		return nil
+	}
+	packet := agent.create_basic_header()
+	packet.packet_type = NAK
+
+	info := new(ControlHeader)
+	info.ctrl_type = 3
+	packet.header_info = info
+
+	packet.cif = cif
+
+	return packet
+}
+
 func (agent *SRTManager) process_data(packet *Packet) (*Packet) {
 	switch packet.packet_type {
 	case DATA:
@@ -227,6 +246,9 @@ func (agent *SRTManager) process_data(packet *Packet) (*Packet) {
 		if time.Now().Sub(agent.pings[len(agent.pings) - 1][0]).Milliseconds() >= 10 {
 			return agent.create_ack_report()
 		}
+		if agent.last_nack.IsZero() || time.Now().Sub(agent.last_nack).Milliseconds() >= 10 {
+			return agent.create_nack_report()
+		}
 	case ACKACK:
 		agent.handle_ackack(packet)
 	default:
@@ -245,6 +267,7 @@ func (agent *SRTManager) handle_data_storage(packet *Packet) {
 	if len(agent.storage.offshoots) != 0 {
 		agent.storage.Relink()
 	}
+	agent.storage.Expunge(agent.output)
 }
 
 func (agent *SRTManager) Process(packet *Packet) (*Packet, error) {
diff --git a/srt/tunnel.go b/srt/tunnel.go
index 2fd169d..ac0acbd 100644
--- a/srt/tunnel.go
+++ b/srt/tunnel.go
@@ -46,6 +46,9 @@ func (tunnel *Tunnel) Shutdown() {
 		info.ctrl_type = 5
 		packet.header_info = info
 		tunnel.WritePacket(packet)
+		if tunnel.state.output != nil {
+			tunnel.state.output.Close()
+		}
 	}
 }