A Zapata

Next-generation 100-gigabit metro ethernet (100 GbME) using multiwavelength optical rings

This paper investigates the challenges for developing the current local area network (LAN)-based Ethernet protocol into a technology for future network architectures that is capable of satisfying dynamic traffic demands with hard service guarantees using high-bit-rate channels (80...100 Gb/s). The objective is to combine high-speed optical transmission and physical interfaces (PHY) with a medium access control (MAC) protocol, designed to meet the service guarantees in future metropolitan-area networks (MANs). Ethernet is an ideal candidate for the extension into the MAN as it allows seamless compatibility with the majority of existing LANs. The proposed extension of the MAC protocol focuses on backward compatibility as well as on the exploitation of the wavelength domain for routing of variable traffic demands. The high bit rates envisaged will easily exhaust the capacity of a single optical fiber in the C band and will require network algorithms optimizing the reuse of wavelength resources. To investigate this, four different static and dynamic optical architectures were studied that potentially offer advantages over current link-based designs. Both analytical and numerical modeling techniques were applied to quantify and compare the network performance for all architectures in terms of achievable throughput, delay, and the number of required wavelengths and to investigate the impact of nonuniform traffic demands. The results show that significant resource savings can be achieved by using end-to-end dynamic lightpath allocation, but at the expense of high delay.

Investigation of the scalability of dynamic wavelength-routed optical networks [Invited]

Feature Issue on Optical Interconnection Networks (OIN). We describe results of the scalability analysis for dynamic wavelength-routed optical networks with end-to-end lightpath assignment and central network control with electronic scheduling and processing of lightpath requests. We investigate the effect of the algorithm complexity in both the scheduling and the dynamic routing and wavelength assignment (DRWA) of lightpath requests. Scheduling theory and static performance-prediction techniques were applied to define the bounds on the electronic processing time of requests, and hence the maximum number of nodes supported by a centralized dynamic optical network for given blocking probability, latency, and network diameter. Scalability analysis results show that medium-sized centralized networks (~50 nodes) can be supported when these networks are reconfigured on a burst-by-burst basis. In addition, we found that real topologies showed a complex trade-off between the request processing time, blocking probability, and resource requirements. These findings can be used to determine the optimum combination of scheduling/DRWA algorithm, showing that the fastest DRWA algorithm does not necessarily lead to the minimum blocking probability and maximum scalability but that a careful consideration of both blocking and processing speed is required. The results are applicable both to dynamic network architectures with centralized request processing such as wavelength-routed optical networks and to the design of advanced optical switching matrices and routers.

Dynamic wavelength-routed optical burst-switched networks: scalability analysis and comparison with static wavelength-routed optical networks

Analytic equations are developed to quantify the maximum network size supported by a centralized dynamic optical network architecture. Comparison with static networks establishes the maximum traffic load for which wavelength resources reduction is achievable.

Fast blocking probability evaluation of end-to-end optical burst switching networks with non-uniform ON–OFF input traffic model

A novel, accurate, numerically stable and fast mathematical method for network-wide blocking probability evaluation of end-to-end optical burst switching (OBS) networks with heterogeneous link capacity under non-uniform traffic is proposed. Unlike most of previous works, which have used the Poisson model for the burst traffic, this paper considers a non-uniform ON–OFF model being a more realistic choice for OBS networks. Compared with simulation, the method was proved to be very accurate and much faster (up to four orders of magnitude faster than simulation in the studied cases). These features make the proposed method very useful for network analysis, especially for large size networks where simulation time can be prohibitively high.

Fast and effective dimensioning algorithm for end-to-end optical burst switching networks with ON-OFF traffic model

A novel algorithm for fast dimensioning of end-to-end optical burst switching networks is proposed. The proposed method determines the number of wavelengths for each network link according to the traffic load, the routing algorithm and the required blocking probability per connection. The burst input traffic is modeled by an ON-OFF alternating renewal process, which is more realistic for OBS networks than the typically used Poisson model. Compared to the two most typically used dimensioning approaches, the proposed method results in significant lower wavelength requirements whilst achieving the same target blocking probability. Additionally, the proposed method takes less than one second to dimension the network links which makes it several orders of magnitude faster than the conventional simulation approach.

Impact of burst aggregation schemes on delay in optical burst switched networks

This work compares the maximum delay in five different burst assembly schemes. The mean packet delay is analytically derived and evaluated by simulation for Poisson and non-Poisson input traffic. The results allow to define an optimum burst assembly scheme in terms of the introduced delay.

Optimal routing for minimum wavelength requirements in end-to-end optical burst switching rings

A novel routing and link dimensioning optimisation method which minimises the total wavelength requirements of dynamic optical WDM rings - the most popular topology in metropolitan networks- is proposed. The method finds the solution (set of routes) of minimum cost by solving an integer linear optimisation problem. Contrary to the common belief, results show that the optimal routes found by the proposed method are not necessarily balanced and that significant wavelength savings are achieved compared to the usual balanced-load routing approach in rings. This makes the proposed method the best choice for implementation in future dynamic WDM ring networks.

Do we really need dynamic wavelength-routed optical networks?

It is widely believed that dynamic operation in wavelength-routed optical networks could overcome the inefficiencies of static allocation in wavelength usage. In this paper this hypothesis is reviewed by quantifying the wavelength requirements in dynamic wavelength-routed optical networks and the comparison of these to those of the static approach. To do so, new analytical and heuristic lower bounds for the wavelength requirements in dynamic networks are proposed. They are used to evaluate the optimality of existing algorithms whose wavelength requirements are evaluated by means of simulation. Results show that dynamic wavelength-routed optical networks can save wavelengths only at low traffic loads (<0.4) and that the highest savings are achieved in sparsely physically connected networks.

Static vs. Dynamic Wavelength-Routed Optical Networks under Time-Varying Traffic

Potential wavelength savings of dynamic WDM networks with respect to static ones are quantified under time-varying traffic. The traffic matrix with the highest traffic load (ρ_max) determines the wavelength savings, observed only for ρ_max<;0.1-0.3.