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Node and Network Architecture

The OPS node and network architecture consisit of a network model, a node model and a number of protocol layer models that can be combined to build nodes to simulate opportunistic networks. A description of these models is given below.

OPS Network Model (OPSNetwork)

OPSNetwork is the network model where all the nodes of the network are defined. All nodes must be of the type KOPSNode and optionally, a model conforming to INotificationGenerator. A KOPSNode contains the protocol stack of an opportunistic networking node. The INotificationGenerator is required when the network is configured to use the user behaviour model identified in Reactive User Behavior and Mobility Models. But a simple user behaviour does not require to use INotificationGenerator. Therefore, by default, no user behaviour modelling is considered. The picture below shows the OPSNetwork model.

OPS Node Model (OPSNetwork)

KOPSNode is the node model used to simulate opprtunisic networks. It is organised in terms of layered protocol stack. Each layer is configured as an interface to plug in different protocol layer implementations. The picture below shows the architecture of the KOPSModel model.

When evaluating the performance of opportunistic networks, the following aspects must be considered before configuring a node.

  1. What application model (Applcation Layer) is used to generate and receive data?

  2. What forwarding model (Forwarding Layer) is used to forward packets by nodes?

  3. What link adaptation model (Link Adaptation Layer) is used if the nodes are overlaid on another transport protocol?

  4. What link layer model (Link Layer) used to make direct communications between nodes?

  5. What mobility model (Mobility) is used to simulated movements of users?

Configuring a node is done using the .ini file. A sample is given here

Application Layer

The application layer generates and injects data into the network. At the same time, it expects data generated by other nodes. There are 3 types of application layers.

User Behaviour Based Application

This application layer is for nodes configured with the user behaviour model identified in Reactive User Behavior and Mobility Models. To cater to the data traffic generation model used in these nodes, a KBasicNotificationGenerator is configured at the network level. This network-wide model holds a set of messages and disseminates to the user behaviour models of nodes. The user behaviour model is a destination-less data dissemination model. The models associated with notification generation are,

  • KBasicNotificationGenerator - Notifications (i.e., messages) are held and disseminated to the user behaviour models of each node to inject them into the network.

The applicatin layer of every node is configured to use the user behaviour model by configuring the following models.

  • KBasicUBM - Performs the enforcement of user preferences on the notifications (messages)
  • KBasicUBMApp - Injects and receives to/from network

Destination Oriented Data Dissemination

This is a simple application model allows the generation of data destined to other nodes. The data is generated (injected to the network) by each node in a round-robin manner. In the single destination mode, all data are sent to one designated node. If this mode is not set, then the data is sent to different destinations. The following model must be configured to use this type of application.

  • KMessengerApp - Injects and receives destination oriented data

Destination-less Data Dissemination

This application model allows the injection of destinaion-less data into the network. This means that these data items are expected by all the nodes in the network (not just one destination). They are injected in a round-robin manner by nodes. The following model must be configured to use this type of application.

  • KHeraldApp - Injects and receives destination-less data based on a cyclic configuration
  • KHeraldAppForDifferentiatedTraffic - Injects and receives destination-less data generated based on different patterns (random or traces)

Forwarding Layer

This layer is configured to forward data and feedback based on the to the forwarding strategy employed. The current forwarding strategies (models) are,

The models KProphetRoutingLayer and KSpraywaitRoutingLayer are, by their nature, destination oriented forwarders. Therefore, they can only be used with a destination oriented application.

Link Adaptation Layer

This layer is tasked with converting packets sent by the forwarder to the specific link technology used (at Link Layer). Currently implemented is a simple pass-through layer.

  • KLinkAdaptLayer - Pass-through layer

Link Layer

This layer implements the operations of a link technology used to perform direct communication between nodes. Currentl models are as follows.

  • KWirelessInterface - A simple wireless interface implementation (without the INET framework)
  • KWirelessInterfaceWithContactTraces - A simple wireless interface implementation using contact traces for contact creation rather than INET mobility models

Mobility Modelling

Movement of nodes is currently handled through the mobility models made available in the INET framework. Therefore, any mobility model that conforms to the INET mobility interface can be used to emulate mobility in opportunistic networks. For the user behaviour based simulations, a special mobility model has been developed to interact with the application. This model, ExtendedSWIMMobility has to be copied into INET and rebuilt before building OPS.