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+.. _mod-nsid:
+
+Name Server Identifier (NSID)
+-----------------------------
+
+This module provides server-side support for :rfc:`5001`
+and is not enabled by default.
+
+DNS clients can request resolver to send back its NSID along with the reply
+to a DNS request.  This is useful for identification of resolver instances
+in larger services (using anycast or load balancers).
+
+
+This is useful tool for debugging larger services,
+as it reveals which particular resolver instance sent the reply.
+
+NSID value can be configured in the resolver's configuration file:
+
+.. code-block:: lua
+
+   modules.load('nsid')
+   nsid.name('instance 1')
+
+You can also obtain configured NSID value:
+
+.. code-block:: lua
+
+   nsid.name()
+   instance 1
+
+The module can be disabled at run-time:
+
+.. code-block:: lua
+
+   modules.unload('nsid')