diff --git a/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SouthboundNetworkGraph.java b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SouthboundNetworkGraph.java
new file mode 100644
index 0000000..cb52d15
--- /dev/null
+++ b/src/main/java/net/onrc/onos/ofcontroller/networkgraph/SouthboundNetworkGraph.java
@@ -0,0 +1,230 @@
+package net.onrc.onos.ofcontroller.networkgraph;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import net.onrc.onos.datastore.RCObject;
+import net.onrc.onos.datastore.topology.RCLink;
+import net.onrc.onos.datastore.topology.RCPort;
+import net.onrc.onos.datastore.topology.RCSwitch;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import edu.stanford.ramcloud.JRamCloud.ObjectDoesntExistException;
+import edu.stanford.ramcloud.JRamCloud.ObjectExistsException;
+import edu.stanford.ramcloud.JRamCloud.WrongVersionException;
+
+/**
+ * The southbound interface to the network graph which allows clients to 
+ * mutate the graph. This class will maintain the invariants of the network
+ * graph. The southbound discovery modules will use this interface to update
+ * the network graph as they learn about the state of the network.
+ *
+ */
+public class SouthboundNetworkGraph {
+	private static final Logger log = LoggerFactory.getLogger(SouthboundNetworkGraph.class);
+	
+	private static final int NUM_RETRIES = 10;
+	
+	
+	public void addSwitch(Switch sw) {
+		RCSwitch rcSwitch = new RCSwitch(sw.getDpid());
+		rcSwitch.setStatus(RCSwitch.STATUS.ACTIVE);
+		
+		for (Port port : sw.getPorts()) {
+			RCPort rcPort = new RCPort(sw.getDpid(), (long)port.getNumber());
+			rcPort.setStatus(RCPort.STATUS.ACTIVE);
+			rcSwitch.addPortId(rcPort.getId());
+			
+			// TODO check how to write switch+ports together
+			writeObject(rcPort);
+		}
+		
+		writeObject(rcSwitch);
+	}
+	
+	public void deactivateSwitch(Switch sw) {
+		RCSwitch rcSwitch = new RCSwitch(sw.getDpid());
+		
+		List<RCObject> objectsToDeactive = new ArrayList<RCObject>();
+		
+		for (int i = 0; i < NUM_RETRIES; i++) {
+			try {
+				rcSwitch.read();
+				rcSwitch.setStatus(RCSwitch.STATUS.INACTIVE);
+				objectsToDeactive.add(rcSwitch);
+				
+				for (Port p : sw.getPorts()) {
+					RCPort rcPort = new RCPort(sw.getDpid(), (long)p.getNumber());
+					rcPort.read();
+					rcPort.setStatus(RCPort.STATUS.INACTIVE);
+					objectsToDeactive.add(rcPort);
+				}
+			} catch (ObjectDoesntExistException e) {
+				log.warn("Trying to deactivate an object that doesn't exist", e);
+				// We don't care to much if the object wasn't there, it's
+				// being deactivated anyway
+			}
+			
+			try {
+				for (RCObject rcObject : objectsToDeactive) {	
+					rcObject.update();
+				}
+				break;
+			} catch (ObjectDoesntExistException e) {
+				// Unlikely, and we don't care anyway. 
+				// TODO But, this will cause everything else to fail
+				log.warn("Trying to deactivate object that doesn't exist", e);
+			} catch (WrongVersionException e) {
+				// Need to re-read and retry
+			}
+		}
+	}
+	
+	public void addPort(Switch sw, Port port) {
+		RCSwitch rcSwitch = new RCSwitch(sw.getDpid());
+		
+		try {
+			rcSwitch.read();
+		} catch (ObjectDoesntExistException e) {
+			log.warn("Add port failed because switch {} doesn't exist", sw.getDpid(), e);
+			return;
+		}
+		
+		RCPort rcPort = new RCPort(port.getSwitch().getDpid(), (long)port.getNumber());
+		rcPort.setStatus(RCPort.STATUS.ACTIVE);
+		rcSwitch.addPortId(rcPort.getId());
+		
+		writeObject(rcPort);
+		writeObject(rcSwitch);
+	}
+	
+	public void deactivatePort(Port port) {
+		RCPort rcPort = new RCPort(port.getSwitch().getDpid(), (long)port.getNumber());
+		
+		for (int i = 0; i < NUM_RETRIES; i++) {
+			try {
+				rcPort.read();
+			} catch (ObjectDoesntExistException e) {
+				// oh well, we were deactivating anyway
+				log.warn("Trying to deactivate a port that doesn't exist: {}", port);
+				return;
+			}
+			
+			rcPort.setStatus(RCPort.STATUS.INACTIVE);
+			
+			try {
+				rcPort.update();
+				break;
+			} catch (ObjectDoesntExistException | WrongVersionException e) {
+				// retry
+			}
+		}
+	}
+	
+	public void addLink(Link link) {
+		RCLink rcLink = new RCLink(link.getSourceSwitchDpid(), (long)link.getSourcePortNumber(),
+				link.getDestinationSwitchDpid(), (long)link.getDestinationPortNumber());
+		
+		RCPort rcSrcPort = new RCPort(link.getSourceSwitchDpid(), (long)link.getSourcePortNumber());
+		RCPort rcDstPort = new RCPort(link.getDestinationSwitchDpid(), (long)link.getDestinationPortNumber());
+		
+		for (int i = 0; i < NUM_RETRIES; i++) {
+			try {
+				rcSrcPort.read();
+				rcDstPort.read();
+				rcLink.create();
+			} catch (ObjectDoesntExistException e) {
+				// port doesn't exist
+				log.error("Add link failed {}", link, e);
+				return;
+			} catch (ObjectExistsException e) {
+				log.debug("Link already exists {}", link);
+				return;
+			}
+			
+			rcSrcPort.addLinkId(rcLink.getId());
+			rcDstPort.addLinkId(rcLink.getId());
+			
+			rcLink.setStatus(RCLink.STATUS.ACTIVE);
+			
+			try {
+				rcLink.update();
+				rcSrcPort.update();
+				rcDstPort.update();
+				break;
+			} catch (ObjectDoesntExistException | WrongVersionException e) {
+				log.debug(" ", e);
+				// retry
+			}
+		}
+	}
+	
+	public void removeLink(Link link) {
+		RCLink rcLink = new RCLink(link.getSourceSwitchDpid(), (long)link.getSourcePortNumber(),
+				link.getDestinationSwitchDpid(), (long)link.getDestinationPortNumber());
+		
+		RCPort rcSrcPort = new RCPort(link.getSourceSwitchDpid(), (long)link.getSourcePortNumber());
+		RCPort rcDstPort = new RCPort(link.getDestinationSwitchDpid(), (long)link.getDestinationPortNumber());
+		
+		for (int i = 0; i < NUM_RETRIES; i++) {
+			try {
+				rcSrcPort.read();
+				rcDstPort.read();
+				rcLink.read();
+			} catch (ObjectDoesntExistException e) {
+				log.error("Remove link failed {}", link, e);
+				return;
+			}
+			
+			rcSrcPort.removeLinkId(rcLink.getId());
+			rcDstPort.removeLinkId(rcLink.getId());
+			
+			try {
+				rcSrcPort.update();
+				rcDstPort.update();
+				rcLink.delete();
+			} catch (ObjectDoesntExistException e) {
+				log.error("Remove link failed {}", link, e);
+				return;
+			} catch (WrongVersionException e) {
+				// retry
+			}
+		}
+	}
+	
+	public void updateDevice(Device device) {
+		// TODO implement
+	}
+	
+	public void removeDevice(Device device) {
+		// TODO implement
+	}
+	
+	// TODO what happens if this fails? why could it fail?
+	private void writeObject(RCObject object) {
+		for (int i = 0; i < NUM_RETRIES; i++) {
+			try {
+				object.create();
+			} catch (ObjectExistsException e) {
+				try {
+					object.read();
+				} catch (ObjectDoesntExistException e1) {
+					// TODO Auto-generated catch block
+					log.error(" ", e);
+					return;
+				}
+			}
+			
+			try {
+				// TODO check API for writing without caring what's there
+				object.update();
+				break;
+			} catch (ObjectDoesntExistException | WrongVersionException e) {
+				log.debug(" ", e);
+				// re-read and retry
+			}
+		}
+	}
+}