diff --git a/src/main/java/net/onrc/onos/core/topology/Link.java b/src/main/java/net/onrc/onos/core/topology/Link.java
new file mode 100644
index 0000000..f73bccf
--- /dev/null
+++ b/src/main/java/net/onrc/onos/core/topology/Link.java
@@ -0,0 +1,66 @@
+package net.onrc.onos.core.topology;
+
+/**
+ * Interface of Link Object exposed to the "NB" read-only Topology.
+ *
+ * Everything returned by these interfaces must be either Unmodifiable view,
+ * immutable object, or a copy of the original "SB" In-memory Topology.
+ *
+ */
+public interface Link {
+    /**
+     * Get the source switch for the link.
+     *
+     * @return the source switch for the link.
+     */
+    public Switch getSrcSwitch();
+
+    /**
+     * Get the source port for the link.
+     *
+     * @return the source port for the link.
+     */
+    public Port getSrcPort();
+
+    /**
+     * Get the destination switch for the link.
+     *
+     * @return the destination switch for the link.
+     */
+    public Switch getDstSwitch();
+
+    /**
+     * Get the destination port for the link.
+     *
+     * @return the destination port for the link.
+     */
+    public Port getDstPort();
+
+    /**
+     * Get the last seen time for the link.
+     *
+     * TODO: Not implemented yet.
+     * TODO: what is the time definition?
+     *
+     * @return the last seen time for the link.
+     */
+    public long getLastSeenTime();
+
+    /**
+     * Get the link cost.
+     *
+     * TODO: What is the unit?
+     *
+     * @param return the link cost.
+     */
+    public int getCost();
+
+    /**
+     * Get the link capacity.
+     *
+     * TODO: What is the unit?
+     *
+     * @return the link capacity.
+     */
+    public Double getCapacity();
+}