diff --git a/ws2012/P2P/uebungen/4/src/network/Network.java b/ws2012/P2P/uebungen/4/src/network/Network.java
new file mode 100644
index 00000000..1bf6a823
--- /dev/null
+++ b/ws2012/P2P/uebungen/4/src/network/Network.java
@@ -0,0 +1,13 @@
+package network;
+
+public class Network {
+
+	
+	//grow a network: Starting with one peer, repeatedly let peers spawn or leave at random
+	public static void main(String[] args) {
+		
+	}
+	
+	
+	
+}
diff --git a/ws2012/P2P/uebungen/4/src/peer/Node.java b/ws2012/P2P/uebungen/4/src/peer/Node.java
new file mode 100644
index 00000000..dfe72755
--- /dev/null
+++ b/ws2012/P2P/uebungen/4/src/peer/Node.java
@@ -0,0 +1,50 @@
+package peer;
+
+import java.util.Iterator;
+import java.util.List;
+
+public class Node {
+	
+	private int id; // node id must be unique! id = IP of peer ?!?
+					//-> Should be unique if we don't consider peers behind a NAT.
+	
+	private List<Node> neighbours;
+	
+	public Node(int id, List<Node> neighbours){
+		this.id 			= id;
+		this.neighbours 	= neighbours;
+	}
+	
+	
+	//add one single neighbour
+	public void addSingleNeighbour(Node neighbour){
+		this.neighbours.add(neighbour);
+	}
+	
+	//add a list of new neighbours
+	public void addMultiNeighbours(List<Node> neighbours){
+		Iterator<Node> it = neighbours.iterator();
+		while(it.hasNext()){
+			this.neighbours.add(it.next());
+		}
+	}
+	
+	public boolean hasNeighbours(){
+		return (this.neighbours.size() > 0);
+	}
+	
+	//checks if actual node has neighbour with given id
+	public boolean hasNeighbour(int id){
+		for(int i = 0; i < neighbours.size(); i++){
+			Node tmp = neighbours.get(i);
+			if(tmp.id == id){
+				return true;
+			}
+		}
+		return false;
+	}
+	
+	
+	
+
+}
diff --git a/ws2012/P2P/uebungen/4/src/peer/Peer.java b/ws2012/P2P/uebungen/4/src/peer/Peer.java
new file mode 100644
index 00000000..c0f14dc6
--- /dev/null
+++ b/ws2012/P2P/uebungen/4/src/peer/Peer.java
@@ -0,0 +1,31 @@
+package peer;
+
+
+public class Peer {
+	
+	private Node node;
+	
+	
+	//create another peer, mutually link creator and spawn
+	public void spawn(){
+		
+	}
+	
+	
+	
+	//circularly link all neighbours, remove itself form all neighbours and exit
+	public void leave(){
+		
+	}
+	
+	
+	
+	
+	
+	
+	
+	
+	
+	
+
+}
diff --git a/ws2012/P2P/uebungen/4/u2.pdf b/ws2012/P2P/uebungen/4/u2.pdf
new file mode 100644
index 00000000..0c21145d
Binary files /dev/null and b/ws2012/P2P/uebungen/4/u2.pdf differ