Yao-Tzung Wang

Mobility management of interconnected virtual LANs over ATM networks

One of the most powerful virtual LAN (VLAN) features is the capability to group users into broadcast domains, which are independent of their locations on the physical network. This paper deals with VLAN services using ATM LAN emulation technology which operates on a client/server model, and focuses on the issues of supporting transparent VLAN services for mobile terminals. A mobile VLAN architecture is proposed to efficiently maintain multiple VLAN broadcast domains over ATM networks even if the topology is changed dynamically due to mobility. This architecture exploits a hypercube over tree (HOT) hierarchical structure, i.e., trees are connected in a hypercube manner, to interconnect different VLANs servers. To filter excessive server-to-server traffic, an intelligent frame forwarding algorithm is proposed for the servers. The proposed mobile VLAN system brings us a step closer towards facilitating mobility and conforms to existing LAN emulation environment.

Interconnection of large-scale LANs via a two-stage switching hub for multimedia applications

As broadband multimedia applications to the desk top are becoming popular today, the high-speed bandwidth demand from a single user will occupy large shares of the LANs channel capacity. Therefore, the evolution of LAN technologies has shifted from shared to dedicated media. More and more LANs are being installed and their interconnection will require parallel switching techniques such as a high-speed switching hub. The ATM small cell-size switching approach is intended to accommodate the mixed media such as voice, data and video. To fulfil the switching cost, bandwidth and latency criteria, a two-stage switching hub for LAN interconnection is designed and presented in this paper. The packet switching technique is used in the first stage switching to efficiently interconnect the local LANs. For the second stage design, the ATM cell switching is adopted to accommodate multimedia traffic and internetworking among LANs and WANs. The switching architecture including both the packet and cell switching units is thoroughly described. The message flow and routing mechanism are presented in the paper. This architecture has been proved to have the advantages of very low latency, flexible scalability and easy routing management with two-way learning.<<ETX>>

Multicast routing for wavelength-routed WDM networks with dynamic membership

Future broadband networks must support integrated services and offer flexible bandwidth usage. In our previous work, we explore the optical link control layer on the top of optical layer that enables the possibility of bandwidth on-demand service directly over wavelength division multiplexed (WDM) networks. Today, more and more applications and services such as video-conferencing software and Virtual LAN service require multicast support over the underlying networks. Currently, it is difficult to provide wavelength multicast over the optical switches without optical/electronic conversions although the conversion takes extra cost. In this paper, based on the proposed wavelength router architecture (equipped with ATM switches to offer O/E and E/O conversions when necessary), a dynamic multicast routing algorithm is proposed to furnish multicast services over WDM networks. The goal is to joint a new group member into the multicast tree so that the cost, including the link cost and the optical/electronic conversion cost, is kept as less as possible. The effectiveness of the proposed wavelength router architecture as well as the dynamic multicast algorithm is evaluated by simulation.

On the support of bandwidth on demand service over wide-area WDM optical networks

Future broadband networks must support integrated services and offer flexible bandwidth usage. Most existing proposals for wide-area wavelength division multiplexed (WDM) networks employ circuit switching adopting the concept of lightpath, in which each circuit or lightpath occupies an entire wavelength. This, however, is not suited for end-to-end transport of information streams, typically with each stream having its unique traffic characteristics such as the bandwidth needed, different traffic bursty nature, and diverse service requirements. In this paper, we explore the extensions of the functions of what we refer as the optical link control (OLC) layer, native on top of optical layer, to offer finer granularity of wavelength usage and further enable the possibility of bandwidth on-demand (BoD) service directly over WDM networks. The objective is to facilitate the support of integrated services over WDM networks and to mitigate the changes needed in the upper layers as well. The proposed approach attempts to exploit the strengths of both optics and electronics, in which packets are either routed end-to-end over a lightpath transparently, or forwarded from wavelength to wavclength by electronic switching, whenever required. Furthermore, in order to establish an end-to-end BoD connection, the issue of how to select the best wavelength to route the given connection is also investigated. The effectiveness of the proposal is evaluated by simulation.