Reliable and scalable network technologies are desired to meet the emerging demand for multimedia communication. Asynchronous Transfer Mode (ATM) is a key technology and its importance is widely recognized. An ATM layer service category, Available Bit Rate (ABR), was specified at the ATM Forum in 1996. ABR is intended to meet the requirements of non-real-time applications that assume best effort data transportation. It has distinctive features compared to other ATM layer categories. We proposed Application Program Interfaces (APIs) for ABR that allow applications to use ABR capability directly. The API is now a part of the ATM Forum specification. In this paper, we describe the background and necessity of ABR APIs and explain the primitives for them in detail. In addition to having common API primitives for requesting bandwidth or delay requirements during connection setup, ABR APIs can exchange feedback information during communication. Applications for such APIs are addressed and their effectiveness is shown by demonstrating simulation for the TCP-ABR interworking for a backbone ABR network. Finally, a migration scenario for utilizing such APIs is proposed.

This paper investigates Available Bit Rate (ABR) traffic control based on the Explicit Forward Congestion Indication (EFCI). A flow control mechanism is specified for ABR service to control the source rate. Resource Management (RM) cells are used to convey feedback. A source sends a forward RM cell for at least every N cells sent. At the destination, a forward RM cell turns around as a backward RM cell and returns to the source. A data cell has EFCI-bit in its header field. A network element sets EFCI-bit if it is congested. A destination indicates congestion status of networks by using RM cells based on the value of the EFCI-bit of the data cells. A one-bit feedback scheme is used by the ATM Forum. However, indication schemes have also been proposed which use explicit indication of source rate based both on values of the EFCI-bit of data cells and on other information contained in a forward RM cell. We evaluated explicit indication schemes as well as a one-bit scheme by simulation. Simulation study showed explicit cell rate indication gives superior performance than one-bit indication especially for long round trip distances. In this paper, we report the results with brief discussion.

In this paper, we first investigate the characteristics of movie contents over the Internet. As in the previous studies, we found the lognormal-distribution well fits the distribution of file size for the whole set of general movie contents. When we specifically focus on the subset that consists of movie trailers, however, it shows different distribution from the lognormal-distribution. Our analysis shows it is similar to an exponential-distribution. We here assume that movie trailers are one of the relevant contents for Contents Delivery Networks (CDN) or Peer-to-Peer (P2P) file exchange communities. We further studies the relationship between playing duration and file size for the movie trailers and we did not find any linear correlation among them. We next consider bandwidth requirements to retrieve movie trailer contents. Our objective is to make it possible for user to view the contents in real-time. Many previous studies investigate bandwidth requirement based only on the file size distribution. In this paper, we analyze the traffic design criteria for CDN or P2P by taking into account both of the results for the file size distribution and the relationship between playing duration and file size for movie trailers. Simulation studies reveal the impact for the bandwidth requirement.

The potential role of a network in improving end-to-end TCP control is considered. Communications in the high-speed network age are revealing the limitations of end-to-end TCP control. Especially, fairness among TCP connections is one such example. Solving these problems requires not only end-to-end control but also active network control. A brief overview of related work is given, followed by the proposal of a method for adjusting the Ack interval based on network information. The principle of our algorithm is based on the relationship between TCP transmission rate at TCP sources and Ack packets intervals from the bottleneck router. Our algorithm implicitly controls transmission rate of TCP sources. Special focus is given to a scenario in which a networks has a bottleneck at a router. Simulation based on the proposed interworking algorithm, called AckAdjust, showed a good end-to-end TCP performance as to fairness between multiple TCP connections in various cases.

In improving channel utilization in microcellular systems, adaptive channel allocation using distributed control has been reported to be effective. We describe an analytical approximation algorithm for channel dimensioning of distributed adaptive channel allocation. We compare our analytical results with simulation results and show the characteristics of permissible load as a function of the number of base station channels based on our method. Finally we illustrate traffic design and administration based on our algorithm.

This paper evaluates the performance of TCP over ATM by simulation studies to clarify its applicability to high-speed WANs. We compared the performance of TCP over ABR with that of TCP over UBR, and TCP over UBR with Early Packet Discard (EPD). As for TCP over UBR, TCP has all responsibilities for end-to-end performance. In this case, cell loss at the ATM layer degrades TCP performance. Optimum tuning of TCP parameters may mitigate this degradation problem, but cannot solve it. Using EPD with UBR can fairly reduce useless transmission of corrupted packets and improve TCP performance, but still have the problem on fairness. As a result, TCP over ABR was proved to be the most effective as long as it suppressed cell loss. It was also proved that, if we want to extract best performance by TCP over ABR, we need to choose TCP parameters such as window size or timer granularity, so that ABR rate control does not interact with TCP window control and retransmission control.

Using Available Bit Rate (ABR) service of Asynchronous Transfer Mode (ATM) at a backbone link will provide a lossless network. It, however, causes congestion at an edge-router and is reported to show poor end-to-end TCP performance. We consider how to improve the performance of TCP over a backbone ABR network. By using ABR feedback information (ACR) at edge-routers, we can adjust intervals of TCP Acknowledgement packets. This adjustment couples the ABR rate-based control loop and the TCP window-based control loop. Based on this scheme, we can achieve a good end-to-end TCP performance as well as good ATM layer performance over backbone ABR. This paper describes comprehensive study on the proposed mechanism.