diff --git a/libraries/networking/src/SentPacketHistory.cpp b/libraries/networking/src/SentPacketHistory.cpp
new file mode 100644
index 0000000000..0ea7fd8b69
--- /dev/null
+++ b/libraries/networking/src/SentPacketHistory.cpp
@@ -0,0 +1,44 @@
+//
+//  SentPacketHistory.cpp
+//  assignement-client/src/octree
+//
+//  Created by Yixin Wang on 6/5/2014
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include "SentPacketHistory.h"
+
+SentPacketHistory::SentPacketHistory(int size)
+    : _sentPackets(size),
+    _newestPacketAt(0),
+    _numExistingPackets(0),
+    _newestSequenceNumber(0)
+{
+}
+
+void SentPacketHistory::packetSent(OCTREE_PACKET_SEQUENCE sequenceNumber, const QByteArray& packet) {
+    _newestSequenceNumber = sequenceNumber;
+
+    // increment _newestPacketAt cyclically, insert new packet there.
+    // this will overwrite the oldest packet in the buffer
+    _newestPacketAt = (_newestPacketAt == _sentPackets.size() - 1) ? 0 : _newestPacketAt + 1;
+    _sentPackets[_newestPacketAt] = packet;
+    if (_numExistingPackets < _sentPackets.size()) {
+        _numExistingPackets++;
+    }
+}
+
+
+const QByteArray* SentPacketHistory::getPacket(OCTREE_PACKET_SEQUENCE sequenceNumber) const {
+    OCTREE_PACKET_SEQUENCE seqDiff = _newestSequenceNumber - sequenceNumber;
+    if (!(seqDiff >= 0 && seqDiff < _numExistingPackets)) {
+        return NULL;
+    }
+    int packetAt = _newestPacketAt - seqDiff;
+    if (packetAt < 0) {
+        packetAt += _sentPackets.size();
+    }
+    return &_sentPackets.at(packetAt);
+}
diff --git a/libraries/networking/src/SentPacketHistory.h b/libraries/networking/src/SentPacketHistory.h
new file mode 100644
index 0000000000..4231400ac1
--- /dev/null
+++ b/libraries/networking/src/SentPacketHistory.h
@@ -0,0 +1,35 @@
+//
+//  SentPacketHistory.h
+//  assignement-client/src/octree
+//
+//  Created by Yixin Wang on 6/5/2014
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#ifndef hifi_SentPacketHistory_h
+#define hifi_SentPacketHistory_h
+
+#include <qbytearray.h>
+#include <qvector.h>
+
+#include "OctreePacketData.h"
+
+class SentPacketHistory {
+
+public:
+    SentPacketHistory(int size);
+
+    void packetSent(OCTREE_PACKET_SEQUENCE sequenceNumber, const QByteArray& packet);
+    const QByteArray* getPacket(OCTREE_PACKET_SEQUENCE sequenceNumber) const;
+
+private:
+    QVector<QByteArray> _sentPackets;    // circular buffer
+    int _newestPacketAt;
+    int _numExistingPackets;
+
+    OCTREE_PACKET_SEQUENCE _newestSequenceNumber;
+};
+
+#endif