diff --git a/core/api/src/main/java/org/onlab/onos/core/IdBlock.java b/core/api/src/main/java/org/onlab/onos/core/IdBlock.java
new file mode 100644
index 0000000..c811e88
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/core/IdBlock.java
@@ -0,0 +1,87 @@
+package org.onlab.onos.core;
+
+import com.google.common.base.MoreObjects;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+/**
+ * A class representing an ID space.
+ */
+public final class IdBlock {
+    private final long start;
+    private final long size;
+
+    private final AtomicLong currentId;
+
+    /**
+     * Constructs a new ID block with the specified size and initial value.
+     *
+     * @param start initial value of the block
+     * @param size size of the block
+     * @throws IllegalArgumentException if the size is less than or equal to 0
+     */
+    public IdBlock(long start, long size) {
+        checkArgument(size > 0, "size should be more than 0, but %s", size);
+
+        this.start = start;
+        this.size = size;
+
+        this.currentId = new AtomicLong(start);
+    }
+
+    /**
+     * Returns the initial value.
+     *
+     * @return initial value
+     */
+    private long getStart() {
+        return start;
+    }
+
+    /**
+     * Returns the last value.
+     *
+     * @return last value
+     */
+    private long getEnd() {
+        return start + size - 1;
+    }
+
+    /**
+     * Returns the block size.
+     *
+     * @return block size
+     */
+    public long getSize() {
+        return size;
+    }
+
+    /**
+     * Returns the next ID in the block.
+     *
+     * @return next ID
+     * @throws UnavailableIdException if there is no available ID in the block.
+     */
+    public long getNextId() {
+        final long id = currentId.getAndIncrement();
+        if (id > getEnd()) {
+            throw new UnavailableIdException(String.format(
+                    "used all IDs in allocated space (size: %d, end: %d, current: %d)",
+                    size, getEnd(), id
+            ));
+        }
+
+        return id;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("start", start)
+                .add("size", size)
+                .add("currentId", currentId)
+                .toString();
+    }
+}