Table Of Contents
Table Of Contents

Visualization

Overview

The INET Framework is able to visualize a wide range of events and conditions in the network: packet drops, data link connectivity, wireless signal path loss, transport connections, routing table routes, and many more. Visualization is implemented as a collection of configurable INET modules that can be added to simulations at will.

Visualizing Network Communication

Visualizing Packet Drops

Several network problems manifest themselves as excessive packet drops, for example poor connectivity, congestion, or misconfiguration. Visualizing packet drops helps identifying such problems in simulations, thereby reducing time spent on debugging and analysis. Poor connectivity in a wireless network can cause senders to drop unacknowledged packets after the retry limit is exceeded. Congestion can cause queues to overflow in a bottleneck router, again resulting in packet drops.

Packet drops can be visualized by including a PacketDropVisualizer module in the simulation. The PacketDropVisualizer module indicates packet drops by displaying an animation effect at the node where the packet drop occurs. In the animation, a packet icon gets thrown out from the node icon, and fades away.

The visualization of packet drops can be enabled with the visualizer’s displayPacketDrops parameter. By default, packet drops at all nodes are visualized. This selection can be narrowed with the nodeFilter, interfaceFilter and packetFilter parameters.

One can click on the packet drop icon to display information about the packet drop in the inspector panel.

Packets are dropped for the following reasons:

  • queue overflow

  • retry limit exceeded

  • unroutable packet

  • network address resolution failed

  • interface down

Visualizing Transport Path Activity

With INET simulations, it is often useful to be able to visualize network traffic. INET provides several visualizers for this task, operating at various levels of the network stack. One of such visualizers is TransportRouteVisualizer that provides graphical feedback about transport layer traffic.

TransportRouteVisualizer visualizes traffic that passes through the transport layers of two endpoints. Adding an IntegratedVisualizer is also an option, because it also contains a TransportRouteVisualizer. Transport path activity visualization is disabled by default, it can be enabled by setting the visualizer’s displayRoutes parameter to true.

TransportRouteVisualizer observes packets that pass through the transport layer, i.e. carry data from/to higher layers.

The activity between two nodes is represented visually by a polyline arrow which points from the source node to the destination node. TransportRouteVisualizer follows packets throughout their path so that the polyline goes through all nodes which are the part of the path of packets. The arrow appears after the first packet has been received, then gradually fades out unless it is reinforced by further packets. Color, fading time and other graphical properties can be changed with parameters of the visualizer.

By default, all packets and nodes are considered for the visualization. This selection can be narrowed with the visualizer’s packetFilter and nodeFilter parameters.

Visualizing Network Path Activity

Network layer traffic can be visualized by including a NetworkRouteVisualizer module in the simulation. Adding an IntegratedVisualizer module is also an option, because it also contains a NetworkRouteVisualizer module. Network path activity visualization is disabled by default, it can be enabled by setting the visualizer’s displayRoutes parameter to true.

NetworkRouteVisualizer currently observes packets that pass through the network layer (i.e. carry data from/to higher layers), but not those that are internal to the operation of the network layer protocol. That is, packets such as ARP, although potentially useful, will not trigger the visualization.

The activity between two nodes is represented visually by a polyline arrow which points from the source node to the destination node. NetworkRouteVisualizer follows packet throughout its path so the polyline goes through all nodes that are part of the packet’s path. The arrow appears after the first packet has been received, then gradually fades out unless it is reinforced by further packets. Color, fading time and other graphical properties can be changed with parameters of the visualizer.

By default, all packets and nodes are considered for the visualization. This selection can be narrowed with the visualizer’s packetFilter and nodeFilter parameters.

Visualizing Routing Tables

In a complex network topology, it is difficult to see how a packet would be routed because the relevant data is scattered among network nodes and hidden in their routing tables. INET contains support for visualization of routing tables, and can display routing information graphically in a concise way. Using visualization, it is often possible to understand routing in a simulation without looking into individual routing tables. The visualization currently supports IPv4.

The RoutingTableVisualizer module (included in the network as part of IntegratedVisualizer) is responsible for visualizing routing table entries.

The visualizer basically annotates network links with labeled arrows that connect source nodes to next hop nodes. The module visualizes those routing table entries that participate in the routing of a given set of destination addresses, by default the addresses of all interfaces of all nodes in the network. That is, it selects the best (longest prefix) matching routes for all destination addresses from each routing table, and shows them as arrows that point to the next hop. Note that one arrow might need to represent several routing entries, for example when distinct prefixes are routed towards the same next hop.

Routing table entries are represented visually by solid arrows. An arrow going from a source node represents a routing table entry in the source node’s routing table. The endpoint node of the arrow is the next hop in the visualized routing table entry. By default, the routing entry is displayed on the arrows in following format:

destination/mask -> gateway (interface)

The format can be changed by setting the visualizer’s labelFormat parameter.

Filtering is also possible. The nodeFilter parameter controls which nodes’ routing tables should be visualized (by default, all nodes), and the destinationFilter parameter selects the set of destination nodes to consider (again, by default all nodes.)

The visualizer reacts to changes. For example, when a routing protocol changes a routing entry, or an IP address gets assigned to an interface by DHCP, the visualizer automatically updates the visualizations according to the specified filters. This is very useful e.g. for the simulation of mobile ad-hoc networks.

Displaying IP Addresses and Other Interface Information

In the simulation of complex networks, it is often useful to be able to display node IP addresses, interface names, etc. above the node icons or on the links. For example, when automatic address assignment is used in a hierarchical network (e.g. using Ipv4NetworkConfigurator), visual inspection can help to verify that the result matches the expectations. While it is true that addresses and other interface data can also be accessed in the GUI by diving into the interface tables of each node, that is tedious, and unsuitable for getting an overview.

The InterfaceTableVisualizer module (included in the network as part of IntegratedVisualizer) displays data about network nodes’ interfaces. (Interfaces are contained in interface tables, hence the name.) By default, the visualization is turned off. When it is enabled using the displayInterfaceTables parameter, the default is that interface names, IP addresses and netmask length are displayed, above the nodes (for wireless interfaces) and on the links (for wired interfaces). By clicking on an interface label, details are displayed in the inspector panel.

The visualizer has several configuration parameters. The format parameter specifies what information is displayed about interfaces. It takes a format string, which can contain the following directives:

  • %N: interface name

  • %4: IPv4 address

  • %6: IPv6 address

  • %n: network address. This is either the IPv4 or the IPv6 address

  • %l: netmask length

  • %M: MAC address

  • %: conditional newline for wired interfaces. The ’’ needs to be escaped with another ’’, i.e. ’%\’

  • %i and %s: the info() and str() functions for the networkInterface class, respectively

The default format string is "%N %\\%n/%l", i.e. interface name, IP address and netmask length.

The set of visualized interfaces can be selected with the configurator’s nodeFilter and interfaceFilter parameters. By default, all interfaces of all nodes are visualized, except for loopback addresses (the default for the interfaceFilter parameter is "not lo\".)

It is possible to display the labels for wired interfaces above the node icons, instead of on the links. This can be done by setting the displayWiredInterfacesAtConnections parameter to false.

There are also several parameters for styling, such as color and font selection.

Visualizing IEEE 802.11 Network Membership

When simulating wifi networks that overlap in space, it is difficult to see which node is a member of which network. The membership may even change over time. It would be useful to be able to display e.g. the SSID above node icons.

IEEE 802.11 network membership can be visualized by including a Ieee80211Visualizer module in the simulation. Adding an IntegratedVisualizer is also an option, because it also contains a Ieee80211Visualizer. Displaying network membership is disabled by default, it can be enabled by setting the visualizer’s displayAssociations parameter to true.

The Ieee80211Visualizer displays an icon and the SSID above network nodes which are part of a wifi network. The icons are color-coded according to the SSID. The icon, colors, and other visual properties can be configured via parameters of the visualizer.

The visualizer’s nodeFilter parameter selects which nodes’ memberships are visualized. The interfaceFilter parameter selects which interfaces are considered in the visualization. By default, all interfaces of all nodes are considered.

Visualizing Transport Connections

In a large network with a complex topology, there might be many transport layer applications and many nodes communicating. In such a case, it might be difficult to see which nodes communicate with which, or if there is any communication at all. Transport connection visualization makes it easy to get information about the active transport connections in the network at a glance. Visualization makes it easy to identify connections by their two endpoints, and to tell different connections apart. It also gives a quick overview about the number of connections in individual nodes and the whole network.

The TransportConnectionVisualizer module (also part of IntegratedVisualizer) displays color-coded icons above the two endpoints of an active, established transport layer level connection. The icons will appear when the connection is established, and disappear when it is closed. Naturally, there can be multiple connections open at a node, thus there can be multiple icons. Icons have the same color at both ends of the connection. In addition to colors, letter codes (A, B, AA, …) may also be displayed to help in identifying connections. Note that this visualizer does not display the paths the packets take. If you are interested in that, take a look at TransportRouteVisualizer, covered in section Visualizing Transport Path Activity.

The visualization is turned off by default, it can be turned on by setting the displayTransportConnections parameter of the visualizer to true.

It is possible to filter the connections being visualized. By default, all connections are included. Filtering by hosts and port numbers can be achieved by setting the sourcePortFilter, destinationPortFilter, sourceNodeFilter and destinationNodeFilter parameters.

The icon, colors and other visual properties can be configured by setting the visualizer’s parameters.

Visualizing The Infrastructure

Visualizing the Physical Environment

The physical environment has a profound effect on the communication of wireless devices. For example, physical objects like walls inside buildings constraint mobility. They also obstruct radio signals often resulting in packet loss. It’s difficult to make sense of the simulation without actually seeing where physical objects are.

The visualization of physical objects present in the physical environment is essential.

The PhysicalEnvironmentVisualizer (also part of IntegratedVisualizer) is responsible for displaying the physical objects. The objects themselves are provided by the PhysicalEnvironment module; their geometry, physical and visual properties are defined in the XML configuration of the PhysicalEnvironment module.

The two-dimensional projection of physical objects is determined by the SceneCanvasVisualizer module. (This is because the projection is also needed by other visualizers, for example MobilityVisualizer.) The default view is top view (z axis), but you can also configure side view (x and y axes), or isometric or ortographic projection.

The visualizer also supports OpenGL-based 3D rendering using the OpenSceneGraph (OSG) library. If the OMNeT++ installation has been compiled with OSG support, you can switch to 3D view using the Qtenv toolbar.

Visualizing Node Mobility

In INET simulations, the movement of mobile nodes is often as important as the communication among them. However, as mobile nodes roam, it is often difficult to visually follow their movement. INET provides a visualizer that not only makes visually tracking mobile nodes easier, but also indicates other properties like speed and direction.

Node mobility of nodes can be visualized by MobilityVisualizer module (included in the network as part of IntegratedVisualizer). By default, mobility visualization is enabled, it can be disabled by setting displayMovements parameter to false.

By default, all mobilities are considered for the visualization. This selection can be narrowed with the visualizer’s moduleFilter parameter.

The visualizer has several important features:

  • Movement Trail: It displays a line along the recent path of movements. The trail gradually fades out as time passes. Color, trail length and other graphical properties can be changed with parameters of the visualizer.

  • Velocity Vector: Velocity is represented visually by an arrow. Its starting point is the node, and its direction coincides with the movement’s direction. The arrow’s length is proportional to the node’s speed.

  • Orientation Arc: Node orientation is represented by an arc whose size is specified by the orientationArcSize parameter. This value is the relative size of the arc compared to a full circle. The arc’s default value is 0.25, i.e. a quarter of a circle.

These features are disabled by default; they can be enabled by setting the visualizer’s displayMovementTrails, displayVelocities and displayOrientations parameters to true.

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