The two previous messages were used to setup reservations. Path Teardown is used to delete an entry in the path state, as well as all dependent reservation state.
The path state is searched in order to find an entry corresponding to the Session object contained in the message. If none is found, the message is discarded silently.
Once found, the Path Teardown message is forwarded to every outgoing interface in order to remove any trace of this path information all along the data path.
Then, every entry in the reservation state corresponding to this path state entry (which means that its Filter_Spec object matches the Sender_Template object of the path state entry) is selected, and the corresponding Filter_Spec is removed in each member of this set. If necessary, the reservation state is deleted.
Finally, the corresponding entry in the path state is removed. Traffic Control is called in order to update the reservations in order to maintain state consistency.