The connection admission control is one of preventive traffic control in ATM networks. The one objective of connection admission control is to keep the network load moderate so as to achieve a performance objective associated with quality of services (QOS). Because the cell loss rate is more sensitive to offered load than the average queuing delay in ATM networks, QOS requirement associated with cell loss rate is considered. The connection admission control acts as one of the major roles in traffic control. The job of connection admission control is to make an acceptance decision for connection set-up request to control the network load. This paper proposed and evaluated a connection admission control method. The proposed method is suitable for real time operation even in large diversity of connection types, because the amount of calculation for connection admission control is reduced remarkably compared to conventional algorithms. Moreover, the amount of calculation for the algorithm does not increase even when the number of connection types increases. The proposed method uses probability function for the number of cells transferred from multiplexed connections and uses recursive equations in estimating cell loss rate.

This paper discusses and evaluates an effect of cell level FEC (Forward Error Correction) capability on error-free (i.e. reliable) IP multicast service over ATM networks. In the error-free IP multicast service, every receiver is delivered IP packet from the sender synchronously. Without applying the FEC policy, the expected IP packet error/loss probability becomes large, when the number of multicast receivers is large. For example, when the cell error/loss probability of each ATM data-link segment is 10-6 and the number of receivers is 103, the IP packet error/loss probability observed at the sender is about 0.5, which means that about 50% of IP packet sent from the sender will be subject to retransmission. One possible solution would be using the intermediate multicast-TCP entities, that terminate TCP protocol, among the sender and the receivers. However, this approach requires the additional entities within the network and can not provide the ordered message delivery for a multipoint-to-multipoint communication. On the contrary, with applying the FEC policy, the expected IP packet error/loss probability is dramatically reduced. Therefore, an error-free IP multicast service can be provided with a simple architecture, even when the number of multicast receiver is large, e.g. 105. For example, when the cell error/loss probability of each ATM data-link segment is 10-6, the packet error/loss probability observed at the sender is less than 10-2 even for 106 receivers. Finally, even when the cell error/loss probability of ATM data-link segment is large, e.g. 10-3, the IP multicast service without the FEC policy can not apply even for 10 receivers. However, the IP multicast with the FEC policy can apply upto few hundred of receivers.

Broadband ISDN based on ATM technologies is expected to offer enhanced and sophisticated services to customers. Since ATM will first be introduced in the business communication world, it will be worth to discuss the future image of desirable ATM customer premises network (CPN). In this paper, we first consider the possible migration scenario of Broadband CPN and some important requirements for the realization of the scenario. Then, we discuss the key issues to be solved for future ATM-CPN, which include network topology, traffic control and connectionless communication services.