diff --git a/libretroshare/src/pqi/pqiqos.cc b/libretroshare/src/pqi/pqiqos.cc
new file mode 100644
index 000000000..b0d6e30f9
--- /dev/null
+++ b/libretroshare/src/pqi/pqiqos.cc
@@ -0,0 +1,79 @@
+#include <iostream>
+#include <list>
+#include <math.h>
+#include <serialiser/rsserial.h>
+
+#include "pqiqos.h"
+
+pqiQoS::pqiQoS(uint32_t nb_levels,float alpha)
+	: _item_queues(nb_levels),_alpha(alpha)
+{
+	assert(pow(alpha,nb_levels) < 1e+20) ;
+
+	float c = 1.0f ;
+	float inc = alpha ;
+	_nb_items = 0 ;
+
+for(int i=((int)nb_levels)-1;i>=0;--i,c *= alpha)
+	{
+		_item_queues[i]._threshold = c ;
+		_item_queues[i]._counter = 0 ;
+		_item_queues[i]._inc = inc ;
+	}
+}
+
+void pqiQoS::print() const
+{
+	std::cerr << "pqiQoS: " << _item_queues.size() << " levels, alpha=" << _alpha ;
+	std::cerr << "  Size = " << _nb_items ;
+	std::cerr << "    Queues: " ;
+	for(uint32_t i=0;i<_item_queues.size();++i)
+		std::cerr << _item_queues[i]._items.size() << " " ;
+	std::cerr << std::endl;
+}
+
+void pqiQoS::in_rsItem(RsItem *item)
+{
+	if(item->priority_level() >= _item_queues.size())
+	{
+		std::cerr << "pqiQoS::in_rsRawItem() ****Warning****: priority " << item->priority_level() << " out of scope [0," << _item_queues.size()-1 << "]. Priority will be clamped to maximum value." << std::endl;
+		item->setPriorityLevel(_item_queues.size()-1) ;
+	}
+
+	_item_queues[item->priority_level()].push(item) ;
+	++_nb_items ;
+}
+
+RsItem *pqiQoS::out_rsItem()
+{
+	// Go through the queues. Increment counters.
+
+	if(_nb_items == 0)
+		return NULL ;
+
+	float inc = 1.0f ;
+	int i = _item_queues.size()-1 ;
+
+	while(i > 0 && _item_queues[i]._items.empty())
+		--i, inc = _item_queues[i]._inc ;
+
+	int last = i ;
+
+	for(int j=i;j>=0;--j)
+		if( (!_item_queues[j]._items.empty()) && ((_item_queues[j]._counter += inc) >= _item_queues[j]._threshold ))
+		{
+			last = j ;
+			_item_queues[j]._counter -= _item_queues[j]._threshold ;
+		}
+
+	if(last >= 0)
+	{
+		assert(_nb_items > 0) ;
+		--_nb_items ;
+		return _item_queues[last].pop();
+	}
+	else
+		return NULL ;
+}
+
+