/**
 * @anchor modules_anchor
 *
 * @defgroup simulator Simulator
 * The "simulator" module contains: 
 *    - a time management class to hold a time and convert between various time units: ns3::Time 
 *    - a scheduler base class used to implement new simulation event schedulers:       
 *      ns3::Scheduler and ns3::SchedulerFactory 
 *    - a simulator class used to create, schedule and cancel events: ns3::Simulator
 *
 * @defgroup core Core
 * \brief The "core" module contains:
 *    - a Functor class: ns3::Callback  
 *    - an os-independent interface to get access to the elapsed wall clock time: ns3::SystemWallClockMs 
 *    - a class to register regression tests with the test manager: ns3::Test and ns3::TestManager
 *    - debugging facilities: \ref logging, \ref assert
 *    - \ref randomvariable
 *    - a base class for objects which need to support per-instance "attributes" and
 *      trace sources: ns3::ObjectBase
 *    - a base class for objects which need to support reference counting
 *      and dynamic object aggregation: ns3::Object
 *    - a smart-pointer class ns3::Ptr designed to work together with ns3::Object
 *    - a configuration class used to set and control all attributes and trace sources
 *      in a simulation: ns3::Config.
 *
 * @defgroup common Common
 * The "common" module contains: 
 *    - a packet class to create and manipulate simulation packets: 
 *      ns3::Packet, ns3::Header,  and ns3::Trailer. This packet class 
 *      also supports per-packet ns3::Tag which are  globs of data 
 *      which can be attached to any packet.
 *
 * @defgroup node Node
 * The "node" module contains:
 *    - a ns3::Node base class which should be subclassed by any new type of
 *      network Node.
 *    - models which abstract the MAC-layer from the IP layer protocols:
 *      ns3::NetDevice and ns3::Channel. 
 *    - models which abstract the application-layer API: ns3::Application,
 *      ns3::Socket, ns3::SocketFactory, and, ns3::Udp
 * 
 *
 * @defgroup devices Devices
 *
 * @defgroup internetStack InternetStack
 * 
 * The "internet-stack" module contains:
 *    - an Ipv4 stack
 *    - an ARP module
 *    - a UDP and a TCP implementation
 *    
 * @defgroup routing Routing
 *
 * @defgroup helper Helpers
 * 
 * @defgroup applications Applications
 *
 * @defgroup mobility Mobility
 *
 * @defgroup constants Constants
 * @brief Constants you can change
 *
 * @defgroup utils Utils
 * @brief The utils directory is for various programs and scripts related 
 * to code coverage, test suites, style checking, and benchmarking.
 * 
 * @defgroup contrib Contrib
 */
