diff --git a/libraries/networking/src/udt/CongestionControl.cpp b/libraries/networking/src/udt/CongestionControl.cpp
index ebbf86ecd8..4f32be0d06 100644
--- a/libraries/networking/src/udt/CongestionControl.cpp
+++ b/libraries/networking/src/udt/CongestionControl.cpp
@@ -1,6 +1,6 @@
 //
 //  CongestionControl.cpp
-//
+//  libraries/networking/src/udt
 //
 //  Created by Clement on 7/23/15.
 //  Copyright 2015 High Fidelity, Inc.
diff --git a/libraries/networking/src/udt/CongestionControl.h b/libraries/networking/src/udt/CongestionControl.h
index fdf8803ec0..fe7f4a15fc 100644
--- a/libraries/networking/src/udt/CongestionControl.h
+++ b/libraries/networking/src/udt/CongestionControl.h
@@ -1,6 +1,6 @@
 //
 //  CongestionControl.h
-//
+//  libraries/networking/src/udt
 //
 //  Created by Clement on 7/23/15.
 //  Copyright 2015 High Fidelity, Inc.
diff --git a/libraries/networking/src/udt/Connection.cpp b/libraries/networking/src/udt/Connection.cpp
index d3b521e054..20d8a9cb92 100644
--- a/libraries/networking/src/udt/Connection.cpp
+++ b/libraries/networking/src/udt/Connection.cpp
@@ -18,6 +18,7 @@
 
 using namespace udt;
 using namespace std;
+using namespace std::chrono;
 
 Connection::Connection(Socket* parentSocket, HifiSockAddr destination) {
     
@@ -29,21 +30,105 @@ void Connection::send(unique_ptr<Packet> packet) {
     }
 }
 
+void Connection::sendACK(bool wasCausedBySyncTimeout) {
+    static const int ACK_PACKET_PAYLOAD_BYTES = sizeof(_lastSentACK) + sizeof(_currentACKSubSequenceNumber)
+        + sizeof(_rtt) + sizeof(_rttVariance) + sizeof(int32_t) + sizeof(int32_t);
+    
+    // setup the ACK packet, make it static so we can re-use it
+    static auto ackPacket = ControlPacket::create(ControlPacket::ACK, ACK_PACKET_PAYLOAD_BYTES);
+    
+    auto currentTime = high_resolution_clock::now();
+    
+    SeqNum nextACKNumber = nextACK();
+    
+    if (nextACKNumber <= _lastReceivedAcknowledgedACK) {
+        // we already got an ACK2 for this ACK we would be sending, don't bother
+        return;
+    }
+    
+    if (nextACKNumber >= _lastSentACK) {
+        // we have received new packets since the last sent ACK
+        
+        // update the last sent ACK
+        _lastSentACK = nextACKNumber;
+        
+        // remove the ACKed packets from the receive queue
+        
+    } else if (nextACKNumber == _lastSentACK) {
+        // We already sent this ACK, but check if we should re-send it.
+        // We will re-send if it has been more than RTT + (4 * RTT variance) since the last ACK
+        milliseconds sinceLastACK = duration_cast<milliseconds>(currentTime - _lastACKTime);
+        if (sinceLastACK.count() < (_rtt + (4 * _rttVariance))) {
+            return;
+        }
+    }
+    
+    // reset the ACK packet so we can fill it up and have it figure out what size it is
+    ackPacket->reset();
+    
+    // pack in the ACK sub-sequence number
+    ackPacket->writePrimitive(_currentACKSubSequenceNumber++);
+    
+    // pack in the ACK number
+    ackPacket->writePrimitive(nextACKNumber);
+    
+    // pack in the RTT and variance
+    ackPacket->writePrimitive(_rtt);
+    ackPacket->writePrimitive(_rttVariance);
+    
+    // pack the available buffer size - must be a minimum of 2
+    
+    if (wasCausedBySyncTimeout) {
+        // pack in the receive speed and bandwidth
+        
+        // record this as the last ACK send time
+        _lastACKTime = high_resolution_clock::now();
+    }
+    
+    // have the send queue send off our packet
+    _sendQueue->sendPacket(*ackPacket);
+}
+
+void Connection::sendLightACK() const {
+    static const int LIGHT_ACK_PACKET_PAYLOAD_BYTES = 4;
+    
+    // create the light ACK packet, make it static so we can re-use it
+    static auto lightACKPacket = ControlPacket::create(ControlPacket::ACK, LIGHT_ACK_PACKET_PAYLOAD_BYTES);
+    
+    SeqNum nextACKNumber = nextACK();
+    
+    if (nextACKNumber == _lastReceivedAcknowledgedACK) {
+        // we already got an ACK2 for this ACK we would be sending, don't bother
+        return;
+    }
+    
+    // pack in the ACK
+    memcpy(lightACKPacket->getPayload(), &nextACKNumber, sizeof(nextACKNumber));
+    
+    // have the send queue send off our packet
+    _sendQueue->sendPacket(*lightACKPacket);
+}
+
+SeqNum Connection::nextACK() const {
+    // TODO: check if we have a loss list
+    return _largestReceivedSeqNum + 1;
+}
+
 void Connection::processReceivedSeqNum(SeqNum seq) {
     // If this is not the next sequence number, report loss
-    if (seq > _largestRecievedSeqNum + 1) {
-        if (_largestRecievedSeqNum + 1 == seq - 1) {
-            _lossList.append(_largestRecievedSeqNum + 1);
+    if (seq > _largestReceivedSeqNum + 1) {
+        if (_largestReceivedSeqNum + 1 == seq - 1) {
+            _lossList.append(_largestReceivedSeqNum + 1);
         } else {
-            _lossList.append(_largestRecievedSeqNum + 1, seq - 1);
+            _lossList.append(_largestReceivedSeqNum + 1, seq - 1);
         }
         
         // TODO: Send loss report
     }
     
-    if (seq > _largestRecievedSeqNum) {
+    if (seq > _largestReceivedSeqNum) {
         // Update largest recieved sequence number
-        _largestRecievedSeqNum = seq;
+        _largestReceivedSeqNum = seq;
     } else {
         // Otherwise, it's a resend, remove it from the loss list
         _lossList.remove(seq);
@@ -52,13 +137,13 @@ void Connection::processReceivedSeqNum(SeqNum seq) {
 
 void Connection::processControl(unique_ptr<ControlPacket> controlPacket) {
     switch (controlPacket->getType()) {
-        case ControlPacket::Type::ACK:
+        case ControlPacket::ACK:
             break;
-        case ControlPacket::Type::ACK2:
+        case ControlPacket::ACK2:
             break;
-        case ControlPacket::Type::NAK:
+        case ControlPacket::NAK:
             break;
-        case ControlPacket::Type::PacketPair:
+        case ControlPacket::PacketPair:
             break;
     }
 }
diff --git a/libraries/networking/src/udt/Connection.h b/libraries/networking/src/udt/Connection.h
index 3b25c7f1b1..f67404a16b 100644
--- a/libraries/networking/src/udt/Connection.h
+++ b/libraries/networking/src/udt/Connection.h
@@ -12,6 +12,7 @@
 #ifndef hifi_Connection_h
 #define hifi_Connection_h
 
+#include <chrono>
 #include <memory>
 
 #include "LossList.h"
@@ -32,13 +33,26 @@ public:
     
     void send(std::unique_ptr<Packet> packet);
     
+    void sendACK(bool wasCausedBySyncTimeout = true);
+    void sendLightACK() const;
+    
+    SeqNum nextACK() const;
+    
     void processReceivedSeqNum(SeqNum seq);
     void processControl(std::unique_ptr<ControlPacket> controlPacket);
     
 private:
-    
     LossList _lossList;
-    SeqNum _largestRecievedSeqNum;
+    SeqNum _largestReceivedSeqNum; // The largest sequence number received from the peer
+    SeqNum _lastSentACK; // The last sent ACK
+    SeqNum _lastReceivedAcknowledgedACK; // The last sent ACK that has been acknowledged via an ACK2 from the peer
+    SeqNum _currentACKSubSequenceNumber; // The current ACK sub-sequence number (used for Acknowledgment of ACKs)
+    
+    int32_t _rtt; // RTT, in milliseconds
+    int32_t _rttVariance; // RTT variance
+    
+    std::chrono::high_resolution_clock::time_point _lastACKTime;
+    
     std::unique_ptr<SendQueue> _sendQueue;
 };
     
diff --git a/libraries/networking/src/udt/ControlPacket.cpp b/libraries/networking/src/udt/ControlPacket.cpp
index a8688f2cdf..8b863c5a21 100644
--- a/libraries/networking/src/udt/ControlPacket.cpp
+++ b/libraries/networking/src/udt/ControlPacket.cpp
@@ -13,8 +13,18 @@
 
 using namespace udt;
 
-std::unique_ptr<ControlPacket> ControlPacket::create(Type type, const SequenceNumberList& sequenceNumbers) {
-    return ControlPacket::create(type, sequenceNumbers);
+std::unique_ptr<ControlPacket> ControlPacket::create(Type type, qint64 size) {
+    
+    std::unique_ptr<ControlPacket> controlPacket;
+    
+    if (size == -1) {
+        return ControlPacket::create(type);
+    } else {
+        // Fail with invalid size
+        Q_ASSERT(size >= 0);
+        
+        return ControlPacket::create(type, size);
+    }
 }
 
 ControlPacket::ControlPacketPair ControlPacket::createPacketPair(quint64 timestamp) {
@@ -25,25 +35,33 @@ ControlPacket::ControlPacketPair ControlPacket::createPacketPair(quint64 timesta
 }
 
 qint64 ControlPacket::localHeaderSize() {
-    return sizeof(TypeAndSubSequenceNumber);
+    return sizeof(ControlBitAndType);
 }
 
 qint64 ControlPacket::totalHeadersSize() const {
     return BasePacket::totalHeadersSize() + localHeaderSize();
 }
 
-ControlPacket::ControlPacket(Type type, const SequenceNumberList& sequenceNumbers) :
-    BasePacket(localHeaderSize() + (sizeof(Packet::SequenceNumber) * sequenceNumbers.size())),
+ControlPacket::ControlPacket(Type type) :
+    BasePacket(-1),
     _type(type)
 {
     adjustPayloadStartAndCapacity();
     
     open(QIODevice::ReadWrite);
     
-    // pack in the sequence numbers
-    for (auto& sequenceNumber : sequenceNumbers) {
-        writePrimitive(sequenceNumber);
-    }
+    writeControlBitAndType();
+}
+
+ControlPacket::ControlPacket(Type type, qint64 size) :
+    BasePacket(localHeaderSize() + size),
+    _type(type)
+{
+    adjustPayloadStartAndCapacity();
+    
+    open(QIODevice::ReadWrite);
+    
+    writeControlBitAndType();
 }
 
 ControlPacket::ControlPacket(quint64 timestamp) :
@@ -54,6 +72,8 @@ ControlPacket::ControlPacket(quint64 timestamp) :
     
     open(QIODevice::ReadWrite);
     
+    writeControlBitAndType();
+    
     // pack in the timestamp
     writePrimitive(timestamp);
 }
@@ -71,3 +91,15 @@ ControlPacket& ControlPacket::operator=(ControlPacket&& other) {
     
     return *this;
 }
+
+static const uint32_t CONTROL_BIT_MASK = 1 << (sizeof(ControlPacket::ControlBitAndType) - 1);
+
+void ControlPacket::writeControlBitAndType() {
+    ControlBitAndType* bitAndType = reinterpret_cast<ControlBitAndType*>(_packet.get());
+
+    // write the control bit by OR'ing the current value with the CONTROL_BIT_MASK
+    *bitAndType = (*bitAndType | CONTROL_BIT_MASK);
+    
+    // write the type by OR'ing the type with the current value & CONTROL_BIT_MASK
+    *bitAndType = (*bitAndType & CONTROL_BIT_MASK) | (_type << sizeof((ControlPacket::Type) - 1));
+}
diff --git a/libraries/networking/src/udt/ControlPacket.h b/libraries/networking/src/udt/ControlPacket.h
index 8b9ccbf073..6d1b7eb5d3 100644
--- a/libraries/networking/src/udt/ControlPacket.h
+++ b/libraries/networking/src/udt/ControlPacket.h
@@ -21,23 +21,21 @@
 
 namespace udt {
     
-using SequenceNumberList = std::vector<Packet::SequenceNumber>;
-    
 class ControlPacket : public BasePacket {
     Q_OBJECT
 public:
-    using TypeAndSubSequenceNumber = uint32_t;
+    using ControlBitAndType = uint32_t;
     using ControlPacketPair = std::pair<std::unique_ptr<ControlPacket>, std::unique_ptr<ControlPacket>>;
     
-    enum class Type : uint16_t {
+    enum Type : uint16_t {
         ACK,
         ACK2,
         NAK,
         PacketPair
     };
     
-    std::unique_ptr<ControlPacket> create(Type type, const SequenceNumberList& sequenceNumbers);
-    ControlPacketPair createPacketPair(quint64 timestamp);
+    static std::unique_ptr<ControlPacket> create(Type type, qint64 size = -1);
+    static ControlPacketPair createPacketPair(quint64 timestamp);
     
     static qint64 localHeaderSize(); // Current level's header size
     virtual qint64 totalHeadersSize() const; // Cumulated size of all the headers
@@ -45,7 +43,8 @@ public:
     Type getType() const { return _type; }
     
 private:
-    ControlPacket(Type type, const SequenceNumberList& sequenceNumbers);
+    ControlPacket(Type type);
+    ControlPacket(Type type, qint64 size);
     ControlPacket(quint64 timestamp);
     ControlPacket(ControlPacket&& other);
     ControlPacket(const ControlPacket& other) = delete;
@@ -53,6 +52,9 @@ private:
     ControlPacket& operator=(ControlPacket&& other);
     ControlPacket& operator=(const ControlPacket& other) = delete;
     
+    // Header writers
+    void writeControlBitAndType();
+    
     Type _type;
 };
 
diff --git a/libraries/networking/src/udt/Packet.cpp b/libraries/networking/src/udt/Packet.cpp
index e9a5636172..a70c3bfbef 100644
--- a/libraries/networking/src/udt/Packet.cpp
+++ b/libraries/networking/src/udt/Packet.cpp
@@ -117,7 +117,6 @@ Packet& Packet::operator=(Packet&& other) {
 static const uint32_t CONTROL_BIT_MASK = 1 << (sizeof(Packet::SequenceNumberAndBitField) - 1);
 static const uint32_t RELIABILITY_BIT_MASK = 1 << (sizeof(Packet::SequenceNumberAndBitField) - 2);
 static const uint32_t MESSAGE_BIT_MASK = 1 << (sizeof(Packet::SequenceNumberAndBitField) - 3);
-static const int BIT_FIELD_LENGTH = 3;
 static const uint32_t BIT_FIELD_MASK = CONTROL_BIT_MASK | RELIABILITY_BIT_MASK | MESSAGE_BIT_MASK;
 
 void Packet::readIsReliable() {
diff --git a/libraries/networking/src/udt/Packet.h b/libraries/networking/src/udt/Packet.h
index 905af15ded..6189be0ef1 100644
--- a/libraries/networking/src/udt/Packet.h
+++ b/libraries/networking/src/udt/Packet.h
@@ -33,8 +33,6 @@ public:
     using MessageNumber = uint32_t;
     using MessageNumberAndBitField = uint32_t;
     
-    static const uint32_t DEFAULT_SEQUENCE_NUMBER = 0;
-
     static std::unique_ptr<Packet> create(qint64 size = -1, bool isReliable = false, bool isPartOfMessage = false);
     static std::unique_ptr<Packet> fromReceivedPacket(std::unique_ptr<char> data, qint64 size, const HifiSockAddr& senderSockAddr);
     
diff --git a/libraries/networking/src/udt/SendQueue.cpp b/libraries/networking/src/udt/SendQueue.cpp
index 7561a7042d..65c1807d19 100644
--- a/libraries/networking/src/udt/SendQueue.cpp
+++ b/libraries/networking/src/udt/SendQueue.cpp
@@ -80,8 +80,8 @@ void SendQueue::stop() {
     _running = false;
 }
     
-void SendQueue::sendPacket(const Packet& packet) {
-    _socket->writeDatagram(packet.getData(), packet.getDataSize(), _destination);
+void SendQueue::sendPacket(const BasePacket& packet) {
+    _socket->writeUnreliablePacket(packet, _destination);
 }
     
 void SendQueue::ack(SeqNum ack) {
diff --git a/libraries/networking/src/udt/SendQueue.h b/libraries/networking/src/udt/SendQueue.h
index 1a1a2fc90d..9c14c19ede 100644
--- a/libraries/networking/src/udt/SendQueue.h
+++ b/libraries/networking/src/udt/SendQueue.h
@@ -26,6 +26,7 @@
 namespace udt {
     
 class Socket;
+class BasePacket;
 class Packet;
     
 class SendQueue : public QObject {
@@ -47,7 +48,7 @@ public:
 public slots:
     void start();
     void stop();
-    void sendPacket(const Packet& packet);
+    void sendPacket(const BasePacket& packet);
     
     void ack(SeqNum ack);
     void nak(std::list<SeqNum> naks);
diff --git a/libraries/networking/src/udt/Socket.cpp b/libraries/networking/src/udt/Socket.cpp
index 8bf7f973ae..6923879201 100644
--- a/libraries/networking/src/udt/Socket.cpp
+++ b/libraries/networking/src/udt/Socket.cpp
@@ -11,6 +11,8 @@
 
 #include "Socket.h"
 
+#include <QtCore/QThread>
+
 #include "../NetworkLogging.h"
 #include "Packet.h"
 
@@ -20,6 +22,12 @@ Socket::Socket(QObject* parent) :
     QObject(parent)
 {
     connect(&_udpSocket, &QUdpSocket::readyRead, this, &Socket::readPendingDatagrams);
+    
+    // make sure our synchronization method is called every SYN interval
+    connect(&_synTimer, &QTimer::timeout, this, &Socket::rateControlSync);
+    
+    // start our timer for the synchronization time interval
+    _synTimer.start(_synInterval);
 }
 
 void Socket::rebind() {
@@ -58,7 +66,7 @@ void Socket::setBufferSizes(int numBytes) {
     }
 }
 
-qint64 Socket::writeUnreliablePacket(const Packet& packet, const HifiSockAddr& sockAddr) {
+qint64 Socket::writeUnreliablePacket(const BasePacket& packet, const HifiSockAddr& sockAddr) {
     return writeDatagram(packet.getData(), packet.getDataSize(), sockAddr);
 }
 
@@ -113,3 +121,14 @@ void Socket::readPendingDatagrams() {
         }
     }
 }
+
+void Socket::rateControlSync() {
+    
+    // TODO: enumerate our list of connections and ask each of them to send off periodic ACK packet for rate control
+    
+    if (_synTimer.interval() != _synInterval) {
+        // if the _synTimer interval doesn't match the current _synInterval (changes when the CC factory is changed)
+        // then restart it now with the right interval
+        _synTimer.start(_synInterval);
+    }
+}
diff --git a/libraries/networking/src/udt/Socket.h b/libraries/networking/src/udt/Socket.h
index b23903501e..f74ea49f0b 100644
--- a/libraries/networking/src/udt/Socket.h
+++ b/libraries/networking/src/udt/Socket.h
@@ -18,13 +18,15 @@
 #include <unordered_map>
 
 #include <QtCore/QObject>
+#include <QtCore/QTimer>
 #include <QtNetwork/QUdpSocket>
 
 #include "../HifiSockAddr.h"
 
 namespace udt {
-    
+
 class BasePacket;
+class ControlSender;
 class Packet;
 class SeqNum;
 
@@ -40,7 +42,7 @@ public:
     
     quint16 localPort() const { return _udpSocket.localPort(); }
     
-    qint64 writeUnreliablePacket(const Packet& packet, const HifiSockAddr& sockAddr);
+    qint64 writeUnreliablePacket(const BasePacket& packet, const HifiSockAddr& sockAddr);
     
     qint64 writeDatagram(const char* data, qint64 size, const HifiSockAddr& sockAddr)
         { return writeDatagram(QByteArray::fromRawData(data, size), sockAddr); }
@@ -59,6 +61,7 @@ public:
 
 private slots:
     void readPendingDatagrams();
+    void rateControlSync();
     
 private:
     QUdpSocket _udpSocket { this };
@@ -68,6 +71,9 @@ private:
     std::unordered_map<HifiSockAddr, BasePacketHandler> _unfilteredHandlers;
 
     std::unordered_map<HifiSockAddr, SeqNum> _packetSequenceNumbers;
+    
+    int32_t _synInterval = 10; // 10ms
+    QTimer _synTimer;
 };
     
 } // namespace udt