diff --git a/tools/ndn-autoconfig/dns-srv.cpp b/tools/ndn-autoconfig/dns-srv.cpp
index 574ef17..bc0b3a6 100644
--- a/tools/ndn-autoconfig/dns-srv.cpp
+++ b/tools/ndn-autoconfig/dns-srv.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2019,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -34,13 +34,14 @@
 #include <arpa/nameser_compat.h>
 #endif
 
+#include <ndn-cxx/util/backports.hpp>
+#include <ndn-cxx/util/exception.hpp>
+
 #include <iostream>
 
 #include <boost/endian/conversion.hpp>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 using namespace std::string_literals;
 
@@ -165,6 +166,4 @@
   return parseSrvRr(queryAnswer, answerSize);
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/dns-srv.hpp b/tools/ndn-autoconfig/dns-srv.hpp
index 41563e9..8d156b1 100644
--- a/tools/ndn-autoconfig/dns-srv.hpp
+++ b/tools/ndn-autoconfig/dns-srv.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -26,11 +26,10 @@
 #ifndef NFD_TOOLS_NDN_AUTOCONFIG_DNS_SRV_HPP
 #define NFD_TOOLS_NDN_AUTOCONFIG_DNS_SRV_HPP
 
-#include "core/common.hpp"
+#include <stdexcept>
+#include <string>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /** \file
  *  \brief provide synchronous DNS SRV record querying
@@ -39,14 +38,9 @@
 class DnsSrvError : public std::runtime_error
 {
 public:
-  explicit
-  DnsSrvError(const std::string& what)
-    : std::runtime_error(what)
-  {
-  }
+  using std::runtime_error::runtime_error;
 };
 
-
 /** \brief Send DNS SRV request for \p fqdn
  *  \param fqdn a fully qualified domain name
  *  \return FaceUri of the hub from the requested SRV record
@@ -62,8 +56,6 @@
 std::string
 querySrvRrSearch();
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_DNS_SRV_HPP
diff --git a/tools/ndn-autoconfig/guess-from-identity-name.cpp b/tools/ndn-autoconfig/guess-from-identity-name.cpp
index 9c50c20..16cf743 100644
--- a/tools/ndn-autoconfig/guess-from-identity-name.cpp
+++ b/tools/ndn-autoconfig/guess-from-identity-name.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -31,9 +31,7 @@
 
 #include <sstream>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 GuessFromIdentityName::GuessFromIdentityName(KeyChain& keyChain)
   : m_keyChain(keyChain)
@@ -62,6 +60,4 @@
   }
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/guess-from-identity-name.hpp b/tools/ndn-autoconfig/guess-from-identity-name.hpp
index 9da9093..2901a55 100644
--- a/tools/ndn-autoconfig/guess-from-identity-name.hpp
+++ b/tools/ndn-autoconfig/guess-from-identity-name.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -29,9 +29,7 @@
 #include "stage.hpp"
 #include <ndn-cxx/security/key-chain.hpp>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /**
  * @brief Guessing home router based on the default identity name
@@ -75,8 +73,6 @@
   KeyChain& m_keyChain;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_GUESS_FROM_IDENTITY_NAME_HPP
diff --git a/tools/ndn-autoconfig/guess-from-search-domains.cpp b/tools/ndn-autoconfig/guess-from-search-domains.cpp
index 2f92cc3..8b32867 100644
--- a/tools/ndn-autoconfig/guess-from-search-domains.cpp
+++ b/tools/ndn-autoconfig/guess-from-search-domains.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -26,9 +26,7 @@
 #include "guess-from-search-domains.hpp"
 #include "dns-srv.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 void
 GuessFromSearchDomains::doStart()
@@ -42,6 +40,4 @@
   }
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/guess-from-search-domains.hpp b/tools/ndn-autoconfig/guess-from-search-domains.hpp
index 9bd6521..fd02b80 100644
--- a/tools/ndn-autoconfig/guess-from-search-domains.hpp
+++ b/tools/ndn-autoconfig/guess-from-search-domains.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -28,9 +28,7 @@
 
 #include "stage.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /**
  * @brief Guessing home router based on DNS query with default suffix
@@ -61,8 +59,6 @@
   doStart() override;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_GUESS_FROM_SEARCH_DOMAINS_HPP
diff --git a/tools/ndn-autoconfig/main.cpp b/tools/ndn-autoconfig/main.cpp
index afedc38..2f8e561 100644
--- a/tools/ndn-autoconfig/main.cpp
+++ b/tools/ndn-autoconfig/main.cpp
@@ -38,11 +38,7 @@
 #include <ndn-cxx/util/scheduler.hpp>
 #include <ndn-cxx/util/time.hpp>
 
-// ndn-autoconfig is an NDN tool not an NFD tool, so it uses ndn::tools::autoconfig namespace.
-// It lives in NFD repository because nfd-start can automatically start ndn-autoconfig in daemon mode.
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 namespace po = boost::program_options;
 
@@ -184,12 +180,10 @@
   return exitCode;
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 int
 main(int argc, char** argv)
 {
-  return ndn::tools::autoconfig::main(argc, argv);
+  return ndn::autoconfig::main(argc, argv);
 }
diff --git a/tools/ndn-autoconfig/multicast-discovery.cpp b/tools/ndn-autoconfig/multicast-discovery.cpp
index a9fbc88..550ed7f 100644
--- a/tools/ndn-autoconfig/multicast-discovery.cpp
+++ b/tools/ndn-autoconfig/multicast-discovery.cpp
@@ -29,9 +29,7 @@
 
 #include <ndn-cxx/encoding/tlv-nfd.hpp>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 using nfd::ControlParameters;
 
@@ -153,6 +151,4 @@
     });
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/multicast-discovery.hpp b/tools/ndn-autoconfig/multicast-discovery.hpp
index a1d5884..b2a63ed 100644
--- a/tools/ndn-autoconfig/multicast-discovery.hpp
+++ b/tools/ndn-autoconfig/multicast-discovery.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -31,9 +31,7 @@
 #include <ndn-cxx/mgmt/nfd/controller.hpp>
 #include <ndn-cxx/mgmt/nfd/face-status.hpp>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /** \brief multicast discovery stage
  *
@@ -87,8 +85,6 @@
   int m_nRegFailure = 0;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_MULTICAST_DISCOVERY_HPP
diff --git a/tools/ndn-autoconfig/ndn-fch-discovery.cpp b/tools/ndn-autoconfig/ndn-fch-discovery.cpp
index 879ea8e..c6df1b7 100644
--- a/tools/ndn-autoconfig/ndn-fch-discovery.cpp
+++ b/tools/ndn-autoconfig/ndn-fch-discovery.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2019,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -31,9 +31,7 @@
 #include <regex>
 #include <sstream>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /**
  * A partial and specialized copy of ndn::FaceUri implementation
@@ -210,6 +208,4 @@
   }
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/ndn-fch-discovery.hpp b/tools/ndn-autoconfig/ndn-fch-discovery.hpp
index 000568d..64d3899 100644
--- a/tools/ndn-autoconfig/ndn-fch-discovery.hpp
+++ b/tools/ndn-autoconfig/ndn-fch-discovery.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -28,9 +28,7 @@
 
 #include "stage.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /**
  * @brief Discovery NDN hub using NDN-FCH protocol
@@ -61,8 +59,6 @@
   std::string m_url;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_NDN_FCH_DISCOVERY_HPP
diff --git a/tools/ndn-autoconfig/procedure.cpp b/tools/ndn-autoconfig/procedure.cpp
index cda39ad..f7295d3 100644
--- a/tools/ndn-autoconfig/procedure.cpp
+++ b/tools/ndn-autoconfig/procedure.cpp
@@ -29,9 +29,7 @@
 #include "multicast-discovery.hpp"
 #include "ndn-fch-discovery.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 using nfd::ControlParameters;
 using nfd::ControlResponse;
@@ -138,6 +136,4 @@
     });
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/procedure.hpp b/tools/ndn-autoconfig/procedure.hpp
index 7c52658..c5dc0bb 100644
--- a/tools/ndn-autoconfig/procedure.hpp
+++ b/tools/ndn-autoconfig/procedure.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2021,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -28,13 +28,13 @@
 
 #include "stage.hpp"
 
+#include "core/common.hpp"
+
 #include <ndn-cxx/face.hpp>
 #include <ndn-cxx/mgmt/nfd/controller.hpp>
 #include <ndn-cxx/security/key-chain.hpp>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 struct Options
 {
@@ -89,8 +89,6 @@
   nfd::Controller m_controller;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_PROCEDURE_HPP
diff --git a/tools/ndn-autoconfig/stage.cpp b/tools/ndn-autoconfig/stage.cpp
index 0569b24..6bfaff0 100644
--- a/tools/ndn-autoconfig/stage.cpp
+++ b/tools/ndn-autoconfig/stage.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2019,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -25,9 +25,7 @@
 
 #include "stage.hpp"
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 void
 Stage::start()
@@ -69,6 +67,4 @@
   m_isInProgress = false;
 }
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
diff --git a/tools/ndn-autoconfig/stage.hpp b/tools/ndn-autoconfig/stage.hpp
index f7f358e..d11309b 100644
--- a/tools/ndn-autoconfig/stage.hpp
+++ b/tools/ndn-autoconfig/stage.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017,  Regents of the University of California,
+ * Copyright (c) 2014-2022,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -26,16 +26,12 @@
 #ifndef NFD_TOOLS_NDN_AUTOCONFIG_STAGE_HPP
 #define NFD_TOOLS_NDN_AUTOCONFIG_STAGE_HPP
 
-#include "core/common.hpp"
-
 #include <ndn-cxx/net/face-uri.hpp>
 #include <ndn-cxx/util/signal.hpp>
 
 #include <iostream>
 
-namespace ndn {
-namespace tools {
-namespace autoconfig {
+namespace ndn::autoconfig {
 
 /** \brief a discovery stage
  */
@@ -45,14 +41,11 @@
   class Error : public std::runtime_error
   {
   public:
-    explicit
-    Error(const std::string& what)
-      : std::runtime_error(what)
-    {
-    }
+    using std::runtime_error::runtime_error;
   };
 
-  virtual ~Stage() = default;
+  virtual
+  ~Stage() = default;
 
   /** \brief get stage name
    *  \return stage name as a phrase, typically starting with lower case
@@ -99,8 +92,6 @@
   bool m_isInProgress = false;
 };
 
-} // namespace autoconfig
-} // namespace tools
-} // namespace ndn
+} // namespace ndn::autoconfig
 
 #endif // NFD_TOOLS_NDN_AUTOCONFIG_STAGE_HPP