Traffic policing in ATM networks with multimedia traffic: the super leaky bucket

Traffic policing and bandwidth management strategies at the User Network Interface (UNI) of an ATM network are investigated by simulation. The network is assumed to transport real time (RT) traffic like voice and video as well as non-real time (non-RT) data traffic. The proposed policing function, called the super leaky bucket (S-LB), is based on the leaky bucket (LB), but handles the three types of traffic differently according to their quality of service (QoS) requirements. Separate queues are maintained for RT and non-RT traffic. They are normally served alternately, but if the number of RT cells exceeds a threshold, it gets non-pre-emptive priority. Further increase of the RT queue causes low priority cells to be discarded. Non-RT cells are buffered and the sources are throttled back during periods of congestion. The simulations clearly demonstrate the advantages of the proposed strategy in providing improved levels of service (delay, jitter and loss) for all types of traffic.

Fatal impact? The effects of emotional arousal and weapon presence on police officers' memories for a simulated crime

Purpose. (1) To investigate the effects of emotional arousal and weapon presence on the completeness and accuracy of police officers' memories; and (2) to better simulate the experience of witnessing a shooting and providing testimony. Methods. A firearms training simulator was used to present 70 experienced police officers with either a shooting or a domestic dispute scenario containing no weapons. Arousal was measured using both self-report and physiological indices. Recall for event details was tested after a 10-minute delay using a structured interview. Identification accuracy was assessed with a photographic line-up. Results. Self-report measures confirmed that the shooting induced greater arousal than did the other scenario. Overall, officers' memories for the event were less complete, but more accurate, when they had witnessed the shooting. The recall and line-up data did not support a weapon focus effect. Conclusions. Police officers' recall performance can be affected both qualitatively and quantitatively by witnessing an arousing event such as a shooting.