Anti-Entropy support for link store.
diff --git a/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/LinkFragmentId.java b/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/LinkFragmentId.java
new file mode 100644
index 0000000..f97bef6
--- /dev/null
+++ b/core/store/dist/src/main/java/org/onlab/onos/store/link/impl/LinkFragmentId.java
@@ -0,0 +1,62 @@
+package org.onlab.onos.store.link.impl;
+
+import java.util.Objects;
+
+import org.onlab.onos.net.LinkKey;
+import org.onlab.onos.net.provider.ProviderId;
+
+import com.google.common.base.MoreObjects;
+
+/**
+ * Identifier for LinkDescription from a Provider.
+ */
+public final class LinkFragmentId {
+    public final ProviderId providerId;
+    public final LinkKey linkKey;
+
+    public LinkFragmentId(LinkKey linkKey, ProviderId providerId) {
+        this.providerId = providerId;
+        this.linkKey = linkKey;
+    }
+
+    public LinkKey linkKey() {
+        return linkKey;
+    }
+
+    public ProviderId providerId() {
+        return providerId;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(providerId, linkKey);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof LinkFragmentId)) {
+            return false;
+        }
+        LinkFragmentId that = (LinkFragmentId) obj;
+        return Objects.equals(this.linkKey, that.linkKey) &&
+               Objects.equals(this.providerId, that.providerId);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("providerId", providerId)
+                .add("linkKey", linkKey)
+                .toString();
+    }
+
+    // for serializer
+    @SuppressWarnings("unused")
+    private LinkFragmentId() {
+        this.providerId = null;
+        this.linkKey = null;
+    }
+}