Tatsuki Ichihashi

An ultra light weight CAC mechanism (UL-CAC) for soft guarantee in ATM networks

CAC (connection admission control) is one of the most important functions in ATM networks to provide various requested QoS from end users. CAC mechanisms for a soft guarantee which assure the requested QoS statistically are classified with a non-parametric or a parametric approach. However, both approaches have disadvantages. The non-parametric approach needs the dedicated hardware to monitor actual traffic streams. Generally, the parametric approach must invoke complicated calculations to analyze mathematical models. The paper proposes a simplified CAC mechanism referred to as UL-CAC (ultra-lightweight CAC) for soft guarantee. Although this mechanism is included in a category of the parametric approach, it does not need complicated calculations. The paper presents its mechanism which is applied to VBR traffic streams characterized by the dual leaky bucket mechanism and is applied to CBR traffic streams. It also verifies suitability by some simulations.

A proposal of flow control mechanism for multicast ABR and its performance

One of the functions that should be provided in ATM LANs is multicast communication. For multicast communication on ATM LANs, the architecture of the switch fabric and protocols for signaling have been studied. However, when data communication using a multicast connection such as a LAN emulation service which expects the high throughput is provided, ABR (available bit rate) service on a multicast connection (multicast ABR) is also required. ABR service has been actively discussed in the ATM Forum. Unfortunately, the study on flow control mechanism for multicast ABR is not sufficient. This paper discusses a suitable flow control mechanism for multicast ABR and shows its performance. At first, it summarizes the approaches for the flow control and describes the outline of the proposed mechanism based on the suitable approach. Next it evaluates the performance and shows the effectiveness of the mechanism by simulations. Moreover, after pointing out the importance of operations in the case of link failures on the multicast tree, it discusses the cooperation in this case between the flow control and the related functions to detect these failures.

New signaling procedures in ATM networks for advance resource reservation

Currently, communication with resource reservation on ATM networks has been required by popularization of multimedia applications. Types of resource reservation are classified into two types according to reservation timing. One type invokes resource reservation just before communication between users. Another type invokes it in advance. In this type, resources can be reserved with communication time periods invoked by a user, well before actual communication. For the former type, several standardization committees, such as the ATM Forum and ITU‐T, have provided some signaling protocols. However, the latter type has no signaling protocol although necessity of this type has increased. This paper presents approaches of this type at first. Next, it proposes new signaling protocols to support this type keeping consistency with the conventional protocols for the former type, and compares proposed protocols. Moreover, it presents mechanisms to reserve resources cooperating with proposed signaling protocols.

Implementing models of the FDDI-II cycle synchronization technique

Abstract This paper considers the cycle synchronization technique of FDDI-II and evaluates it on some possible implementation models. In an FDDI ring system, each station determines the bit clock of data transmitted therefrom. In an FDDI-II system also supporting a circuit-switched service, 125 μs cycles are generated and circulated on a ring from a master station, and each slave station synchronizes to them. The smoothing function of the physical layer in each station adjusts the length of the preamble to transmit data without loss. We explored five models of stations and simulated cycle circulation operation on a ring to verify the smoothing functions effectiveness and the propriety of the FDDI-II cycle synchronization technique.