In ATM networks Connection Admission Control (CAC) is a key part of traffic control but several challenging problems still remain. One is how to assign sufficient bandwidth fast enough to achieve real-time CAC. Although solutions to the bandwidth assignment problem have been proposed, they require a lot of calculations depending on the number of VCs and on the number of different VC types. Therefore, it is difficult to apply these solutions to real-time CAC decisions, This paper presents a cell-loss ratio evaluation algorithm that takes the peak and the average cell rates as inputs, and providers the upper-bound of the cell-loss ratio. The most remarkable characteristic of this algorithm is that it does not require exhaustive calculation and its calculation load is independent of the number of VCs and the number of different VC types. Using this approximation, we propose a real-time CAC. The experimental results show that call processing of the proposed CAC using a processor, whose pertormance is almost the same as that of a processor in a conventional PBX, terminates within several milliseconds.

This paper proposes a hybrid access control scheme for broadcast-based ATM-LANs. Broadcast-based ATM-LANs are shared media networks with star topology. In this network, packets are broadcast to all subscriber terminals by a CPYF (Cell COPY Function) node located in the ATM network and only relevant packets are extracted and sent to the destined user layer function by packet filtering functions in the terminals. The simplicity of the packet transfer mechanism makes the network very economical. In broadcast-based ATM-LANs, the hybrid access control scheme is effective in improving performance. In this scheme, short packets and long packets are transmitted respectively by means of a back-pressure type and a CSMA/CD type access control scheme. Throughput evaluation was performed by computer simulation and the results show that the proposed scheme achieves a high throughput characteristic.

Originally intended for application to B-ISDN, which is carrier oriented, ATM technology has been actively studied for application to LAN based environments since the beginning of the 1990s. One of the most notable things in LAN area is development of a rich set of application services. A number of technical specifications for major application services have been developed, which include LAN Emulation, IP over ATM, Multi-protocol over ATM, Voice and Telephony over ATM, as well as Native ATM services such as MPEG2 over ATM. Development of these new services raises new challenges related to traffic management. Keeping pace with the development, a number of traffic control mechanisms have also been developed to maximize the performance of these services. Traffic control and management techniques, however, are still in the early stage of their learning curve. Network engineers are facing challenging problems related to traffic management. This paper reviews major service-related technologies and discusses traffic management issues associated with these services. Especially, it describes the real world traffic management as practiced by average network engineers with state-of-the-art products. Although the thechnology developments have advanced through many research works, there seems to be a considerable gaps between the practice and principles. This paper discusses the traffic issues of ATM LAN from this perspective and points out some challenges for the future. Most of the difficulties in handling traffic issues stems from the differences in implementation details. To alleviate this difficulty, the introduction of a unified node model which describes the traffic handling capability of ATM nodes in sufficient detail is suggested.