HOWTO determine the path of an attribute or trace source

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Aggregated Objects

$-prefixed items in a path are used to perform an aggregation lookup using the TypeId of the Object you are looking for. Since almost all TypeIds have a ns3:: prefix, you will usually see the compound prefix $ns3::



the above path works because ns3::TcpL4Protocol instances are aggregated to the node in which they exist. On the other hand see this one:


the above path is getting device 0 in node 0, and, then, doing GetObject<WifiRemoteStationManager> on it but it gets null because the remote station manager is not aggregated to the device.

Objects of a specific type

$-prefixed items in a path are also used to do a type cast to an object of a particular type.

For example:


will match only with devices of type WifiNetDevice.

Conversely, the following:


will match with any device, regardless of the type.

Objects referenced by attributes of other Objects

2) non-$ prefixed non-terminating items in a path are used to perform an attribute lookup on an attribute of type Pointer. This is often used as an alternative to object aggregation.

As an example, when using a wifi device:


the above path works, because devices with TypeId ns3::WifiNetDevice have a RemoteStationManager attribute which is of type Ptr<WifiRemoteStationManager>. On the other hand, see this one:

the above path doesn't work,
gets you to a Node Object, and there is no Attribute named TcpL4Protocol. All this in spite of the fact that TcpL4Protocol is aggregated with Node -- remember that for querying aggregated objects you need the $ prefix.


  • A nice way to figure out a path is to use the ConfigStore: if you use it to dump all attributes in a text file, you can see a valid path for each attribute (this, arguably, does not work for trace sources).
  • Also, note that there is a 'Config' LogComponent: just activate it by stating LogComponentEnable ("Config", LOG_LEVEL_ALL); somewhere in your simulation script.