LightRing: An integrated WDM ring network solution for optical metropolitan area networks.

摘要

The challenge in a metropolitan area network (MAN) is to provide fast, flexible, and cost-effective service. This translates into providing a flexible network with high capacity and low cost. Two effective approaches can be explored in this regard. The first is to simplify the network protocol stack. This means to replacing the complex, voice-optimized SONET/SDH equipment with less costly, data-optimized, lower layer equipment. The challenge then becomes implementing simple protocols that match or exceed the functionality provided in SONET, i.e., survivability, management, error detection/correction, and so forth.; The second approach to improve cost/capacity efficiency in a MAN is through dynamic bandwidth provisioning. Due to the diversity and dynamics of MAN traffic, this approach plays a critical role in improving efficiency.; With the aim to design a cost/functionality- and cost/capacity-efficient MAN architecture, we propose, in this thesis, an innovative multi-token controlled Wavelength Division Multiplexing (WDM) ring solution (termed LightRing) with integrated dynamic “tell and-go” lightpath switching and optical packet switching.; To achieve dynamic lightpath on-demand, the LightRing solution applies a distributed and contention-free multi-token reservation mechanism for lightpath setup and teardown. Therefore, there is no single point of failure and bottleneck as in the centralized approach. To achieve high efficiency and low node cost for packet switching, the LightRing solution applies a dynamic control on the token holding time based on a target token inter-arrival time. These two alternative switching techniques are dynamically selected by a novel multi-token control protocol that regulates the transmissions of the nodes on the ring with the aim of complying with the service-level agreements of customers, maximizing the network bandwidth utilization, and minimizing the network latency under dynamic MAN traffic. This solution circumvents the latency problem (being too slow to switch packets) of current optical switching components by using of ring latency compensation. The proposed architecture and protocol are good candidates for designing IP over WDM networks for metropolitan areas because they do not require the cumbersome multi-layered approach based on ATM and SONET/SDH, and they provide all-optical transmission by means of extant optical technology. Although not specifically addressed in this thesis, multicast and self-healing reconfiguration are additional features of the proposed LightRing architecture.; Both analytical and simulation modeling techniques are used to assess the LightRing performance in the thesis. Compared with the dynamic centralized bandwidth allocation approach and packet switching based on target token rotation time, the performance results demonstrate that the LightRing's distributed control yields short set-up time (for lightpath) and access delay (for packet switching), that can be well below the ring round-trip propagation time, fair blocking probability, and high bandwidth utilization.