o set up connection with another ATM device, it sends a signalling request directly to the connected ATM switch. The signalling request packets contain the end destination point address and any desired QoS parameter for the virtual connection. The signalling packet is reassembled by the switches and is examined to see whether it has the resources along with the desired QoS parameters to set up such a connection. It then sets up a VC on the input links and subsequently forwards the request out of the interface as specified in its switching table to the next ATM switch for further analysis, until it reaches the destination. 'V' connections are then set up along the path going to the end destination as every switch on the route examines the signalling packet and forwards it to the next switch. If a switch is not able DETAILED PLANNING to provide the desired QoS, the request is rejected and a message is then sent back to the point of origination. If the end point can support the desired QoS, it responds with accept messages as well as VCI/VPI values that the originator should use for the cells destined to the end point. Upon acceptance of the connections, traffic management functions ensure that each of the connections adheres to the traffic contract as agreed. This involves traffic management functions and techniques such as: traffic parameters connection admission control (CAC) conformance monitoring and control queuing. Traffic Parameters We have seen different types of service classes (CBR, UBR, etc.) available in ATM. Each of these service classes is defined by a set of traffic parameters, which describes the charac- teristic of the traffic source. These parameters are set to ensure a proper resource allocation to provide a guaranteed bandwidth and adhere to the desired QoS across the ATM network. The most common traffic parameters are as follows: Peak cell rate (PCR): This is defined as the maximum instantaneous rate that the user will transmit. It can be calculated as the inverse of the minimum time interval b