Added more event and listener interface definitions.
diff --git a/net/api/src/main/java/org/onlab/onos/net/Link.java b/net/api/src/main/java/org/onlab/onos/net/Link.java
new file mode 100644
index 0000000..2087377
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/Link.java
@@ -0,0 +1,24 @@
+package org.onlab.onos.net;
+
+import org.onlab.onos.net.provider.Provided;
+
+/**
+ * Abstraction of a network infrastructure link.
+ */
+public interface Link extends Provided { // TODO: Also should extend graph Edge
+
+ /**
+ * Returns the link source connection point.
+ *
+ * @return link source connection point
+ */
+ ConnectPoint src();
+
+ /**
+ * Returns the link destination connection point.
+ *
+ * @return link destination connection point
+ */
+ ConnectPoint dst();
+
+}