diff --git a/ackhandler/ack_handler.go b/ackhandler/ack_handler.go
new file mode 100644
index 00000000..b05637cc
--- /dev/null
+++ b/ackhandler/ack_handler.go
@@ -0,0 +1,52 @@
+package ackhandler
+
+import "github.com/lucas-clemente/quic-go/protocol"
+
+// The AckHandler handles ACKs
+type AckHandler struct {
+	LargestObserved protocol.PacketNumber
+	Observed        map[protocol.PacketNumber]bool
+}
+
+// NewAckHandler creates a new AckHandler
+func NewAckHandler() (*AckHandler, error) {
+	ackHandler := &AckHandler{
+		Observed: make(map[protocol.PacketNumber]bool),
+	}
+	return ackHandler, nil
+}
+
+// HandlePacket handles a packet
+func (h *AckHandler) HandlePacket(packetNumber protocol.PacketNumber) {
+	if packetNumber > h.LargestObserved {
+		h.LargestObserved = packetNumber
+	}
+	h.Observed[packetNumber] = true
+}
+
+// GetNackRanges gets all the NACK ranges
+func (h *AckHandler) GetNackRanges() []*NackRange {
+	// ToDo: improve performance
+	var ranges []*NackRange
+	inRange := false
+	// ToDo: fix types
+	for i := 0; i < int(h.LargestObserved); i++ {
+		packetNumber := protocol.PacketNumber(i)
+		_, ok := h.Observed[packetNumber]
+		if !ok {
+			if !inRange {
+				r := &NackRange{
+					FirstPacketNumber: packetNumber,
+					Length:            1,
+				}
+				ranges = append(ranges, r)
+				inRange = true
+			} else {
+				ranges[len(ranges)-1].Length++
+			}
+		} else {
+			inRange = false
+		}
+	}
+	return ranges
+}
diff --git a/ackhandler/ack_handler_test.go b/ackhandler/ack_handler_test.go
new file mode 100644
index 00000000..145dbd55
--- /dev/null
+++ b/ackhandler/ack_handler_test.go
@@ -0,0 +1,84 @@
+package ackhandler
+
+import (
+	"github.com/lucas-clemente/quic-go/protocol"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("AckHandler", func() {
+	It("Returns no NACK ranges for continously received packets", func() {
+		ackHandler, _ := NewAckHandler()
+		for i := 0; i < 100; i++ {
+			ackHandler.HandlePacket(protocol.PacketNumber(i))
+		}
+		Expect(ackHandler.LargestObserved).To(Equal(protocol.PacketNumber(99)))
+		Expect(len(ackHandler.GetNackRanges())).To(Equal(0))
+	})
+
+	It("handles a single lost package", func() {
+		ackHandler, _ := NewAckHandler()
+		for i := 0; i < 10; i++ {
+			if i == 5 {
+				continue
+			}
+			ackHandler.HandlePacket(protocol.PacketNumber(i))
+		}
+		Expect(ackHandler.LargestObserved).To(Equal(protocol.PacketNumber(9)))
+		nackRanges := ackHandler.GetNackRanges()
+		Expect(len(nackRanges)).To(Equal(1))
+		Expect(nackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(5)))
+		Expect(nackRanges[0].Length).To(Equal(uint8(1)))
+	})
+
+	It("handles two consecutive lost packages", func() {
+		ackHandler, _ := NewAckHandler()
+		for i := 0; i < 10; i++ {
+			if i == 5 || i == 6 {
+				continue
+			}
+			ackHandler.HandlePacket(protocol.PacketNumber(i))
+		}
+		Expect(ackHandler.LargestObserved).To(Equal(protocol.PacketNumber(9)))
+		nackRanges := ackHandler.GetNackRanges()
+		Expect(len(nackRanges)).To(Equal(1))
+		Expect(nackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(5)))
+		Expect(nackRanges[0].Length).To(Equal(uint8(2)))
+	})
+
+	It("handles two non-consecutively lost packages", func() {
+		ackHandler, _ := NewAckHandler()
+		for i := 0; i < 10; i++ {
+			if i == 3 || i == 7 {
+				continue
+			}
+			ackHandler.HandlePacket(protocol.PacketNumber(i))
+		}
+		Expect(ackHandler.LargestObserved).To(Equal(protocol.PacketNumber(9)))
+		nackRanges := ackHandler.GetNackRanges()
+		Expect(len(nackRanges)).To(Equal(2))
+		Expect(nackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(3)))
+		Expect(nackRanges[0].Length).To(Equal(uint8(1)))
+		Expect(nackRanges[1].FirstPacketNumber).To(Equal(protocol.PacketNumber(7)))
+		Expect(nackRanges[1].Length).To(Equal(uint8(1)))
+	})
+
+	It("handles two sequences of lost packages", func() {
+		ackHandler, _ := NewAckHandler()
+		for i := 0; i < 10; i++ {
+			if i == 2 || i == 3 || i == 4 || i == 7 || i == 8 {
+				continue
+			}
+			ackHandler.HandlePacket(protocol.PacketNumber(i))
+		}
+		Expect(ackHandler.LargestObserved).To(Equal(protocol.PacketNumber(9)))
+		nackRanges := ackHandler.GetNackRanges()
+		Expect(len(nackRanges)).To(Equal(2))
+		Expect(nackRanges[0].FirstPacketNumber).To(Equal(protocol.PacketNumber(2)))
+		Expect(nackRanges[0].Length).To(Equal(uint8(3)))
+		Expect(nackRanges[1].FirstPacketNumber).To(Equal(protocol.PacketNumber(7)))
+		Expect(nackRanges[1].Length).To(Equal(uint8(2)))
+	})
+
+})
diff --git a/ackhandler/ackhandler_suite_test.go b/ackhandler/ackhandler_suite_test.go
new file mode 100644
index 00000000..53108c19
--- /dev/null
+++ b/ackhandler/ackhandler_suite_test.go
@@ -0,0 +1,13 @@
+package ackhandler
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"testing"
+)
+
+func TestCrypto(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "AckHandler Suite")
+}