The dramatic growth in e-business is strengthening demands for the collocation of enterprise servers in highly reliable data centers and high-speed connections between several local area networks (LANs). The emergence of low-cost and high-speed Ethernet-based networks, such as fast Ethernet (100 MbE) and GbE, are accelerating these demands: data-center services, and virtual LAN (VLAN) or IP-based virtual private network (IP-VPN) services are beginning to be offered via wide area networks (WANs) [5].

The most effective way of implementing such services is to consolidate the switching equipment and information servers into the CN and directly connect each user to the CN. This minimizes the burden of operation and maintenance for the switches and servers while offering wide service areas (several tens of kilometers radius). Although such switching node consolidation has been reported through the use of time-division multiple access technology [5], the reported network shared 2.5 Gbps bandwidth among all users under synchronous time slot control, thus making it difficult to realize guaranteed gigabit services.

This section describes a wide-area access network that directly connects the users to the CN through the use of WDM; each user occupies two fixed wavelengths (up-and downstream). The network consolidates the switches in the CN, thus minimizing the burden of system operation and maintenance. To decrease the number of optical fibers used while keeping ...

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