/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * Copyright (c) 2009 IITP RAS

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 *

 * Authors:     Kirill Andreev <andreev@itp.ru>      

 *              Aleksander Safonov <safa@iitp.ru>

 *              Pavel Boyko <boyko@iitp.ru>

 *

 * This is top level mesh module description

 */

/**

 * \ingroup devices

 * \defgroup mesh Mesh

 *

 * \brief MAC-layer mobile mesh networking.

 * \section MeshOverview Overview of Layer-2 Mesh networking protocols

 * 

 * The main goal of this module is to provide MAC-layer routing functionality.

 * The main part of MAC-layer routing model is specific type of a network device -- 

 * ns3::MeshPointDevice. Being an interface to upper-layer protocols, it provides routing functionality

 * hidden from upper-layer protocols, by means of ns3::MeshL2RoutingProtocol. 

 * 

 * Our model supports stations with multiple network devices handled by a single

 * MAC-layer routing protocol. So, ns3::MeshPointDevice serves as an umbrella to multiple 

 * network devices ("interfaces")  working under the same MAC-layer routing protocol.

 * 

 * Network devices may be of different types, each with a specific medium access method.

 * So ns3::MeshL2RoutingProtocol consists of two parts: the one independent from the network device type, 

 * which we refer to as a routing protocol, and the other one depended on the network device type which

 * we refer to as a plug-in to the routing protocol.

 * 

 * One can imagine a MAC-layer routing as a two-tier model. ns3::MeshL2RoutingProtocol and ns3::MeshPointDevice 

 * belong to the upper tier. The task of ns3::MeshPointDevice is to send, receive, and forward frames, 

 * while the task of ns3::MeshL2RoutingProtocol is to resolve routes and keep frames waiting for route resolution. 

 * This functionality is independent from the types of underlying network devices ("interfaces").

 * 

 * The lower tier implements the part of MAC-layer routing, specific for underlying network devices

 * and their medium access control methods. For example, HWMP routing protocol in IEEE802.11s

 * uses its own specific management frames.

 * 

 * At present, two routing protocols are implemented in this module:

 *      - HWMP (default routing protocol for IEEE802.11s standard) + Peer management protocol 

 *      (also described in 802.11s standard draft) which is required by HWMP to manage peer links 

 *      (it works like association mechanism in IEEE802.11).

 *      - FLAME (Forwarding LAyer for MEshing).

 * While HWMP only works with 802.11-MAC, FLAME works with all types of network devices, which support

 * 48-bit MAC-addressing scheme.

 * 

 * \subsection Architecture Architecture of MAC-layer routing stack

 * As already mentioned, MAC-layer routing consists of two tiers.

 * An ns3::MeshPointDevice which forwards frames by using an attached ns3::MeshL2RoutingProtocol forms 

 * the upper tier. The interface between ns3::MeshPointDevice and the upper-layer protocols is inherited 

 * from ns3::NetDevice class. The ns3::MeshPointDevice interacts with ns3::MeshL2RoutingProtocol as follows:

 * ns3::MeshPointDevice gives to ns3::MeshL2RoutingProtocol a frame with the source and destination addresses,

 * the network device index which the frame is received from, and a callback to be executed when the route is found.

 * The callback is needed because all routing queues are implemented inside ns3::MeshL2RoutingProtocol. 

 * When the route is resolved, ns3::MeshL2RoutingProtocol returns the frame back to ns3::MeshPointDevice with the 

 * network device index which the packet shall be sent to. All additional routing information is stored inside 

 * the frame by means of tags. In the end, when all these routines are done, the frame goes to the lower tier.

 * The lower tier is responsible for filling MAC-specific headers. At present, we have only implemented the

 * lower tier which is specific for ns3::WifiNetDevice. This tier is implemented as two base classes: 

 * ns3::MeshWifiInterfaceMac and ns3::MeshWifiInterfaceMacPlugin. The former is a new kind of WifiMac. If beacon 

 * generation is enabled or disabled, it implements IEEE802.11s mesh functionality or a simple ad hoc functionality 

 * of the MAC-high part of the WiFi model, respectively. The latter is a plug-in to L2Routing protocol. 

 * It handles all outgoing and incoming frames, fills headers and make decisions to drop a frame or not. Also, it 

 * adds information elements to beacons specific to given L2Routing protocol, if needed.

 * \image html MeshArchitecture.png "Overview of the Mesh MAC-layer routing system"

 * 

 * \subsection NewProtocol Adding a new protocol

 * This module requires all the network devices operate with ns3::Mac48Address addressing scheme.

 * 

 * To add a new L2Routing protocol, one needs to define the following:

 *      - Write an upper part of the protocol inherited from ns3::MeshL2Routing.

 *      - If the protocol works only with 802.11 MAC -- write a plug-in inherited from ns3::MeshWifiInterfaceMacPlugin

 *      - If the protocol works with other types of network devices -- write your own plug-in (interface for

 *      communication with other types of network devices is not implemented).

 * 

 * When you implement a L2Routing protocol, remember that when you are at L2Routing tier, 

 * you work with a frame without an LLC header, and when you are at plug-in tier using 

 * ns3::MeshWifiInterfaceMacPlugin, an LLC header is already attached (by WifiNetDevice)

 * 

 * \attention Note, when you use ns3::MeshWifiInterfaceMac, multiple plug-ins may be installed. 

 * 

 * \subsection Statistics

 * Each L2Routing protocol has a structure to capture statistics, Report and ResetStats methods.

 * This gives an opportunity to collect statistic to an *.xml file periodically.

 */