Michael Düser

Analysis of a dynamically wavelength-routed optical burst switched network architecture

The concept of optical burst switching (OBS) aims to allow access to optical bandwidth in dense wavelength division multiplexed (DWDM) networks at fractions of the optical line rate to improve bandwidth utilization efficiency. This paper studies an alternative network architecture combining OBS with dynamic wavelength allocation under fast circuit switching to provide a scalable optical architecture with a guaranteed QoS in the presence of dynamic and bursty traffic loads. In the proposed architecture, all processing and buffering are concentrated at the network edge and bursts are routed over an optical transport core using dynamic wavelength assignment. It is assumed that there are no buffers or wavelength conversion in core nodes and that fast tuneable laser sources are used in the edge routers. This eliminates the forwarding bottleneck of electronic routers in DWDM networks for terabit-per-second throughput and guarantees forwarding with predefined delay at the edge and latency due only to propagation time in the core. The edge burst aggregation mechanisms are evaluated for a range of traffic statistics to identify their impact on the allowable burst lengths, required buffer size and achievable edge delays. Bandwidth utilization and wavelength reuse are introduced as new parameters characterizing the network performance in the case of dynamic wavelength allocation. Based on an analytical model, upper bounds for these parameters are derived to quantify the advantages of wavelength channel reuse, including the influence of the signaling round-trip time required for lightpath reservation. The results allow to quantify the operational gain achievable with fast wavelength switching compared to quasistatic wavelength-routed optical networks and can be applied to the design of future optical network architectures.

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.

Performance of a dynamically wavelength-routed optical burst switched network

This letter describes a novel network architecture combining optical burst switching with dynamic wavelength allocation to achieve a guaranteed quality of service. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Burst aggregation is evaluated for a range of traffic statistics in terms of delay and packet loss rate, and an analytical model is given to quantify the benefits of dynamic wavelength reuse. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength-routed optical networks.

Performance of a dynamically wavelength-routed, optical burst switched network

This letter describes a novel network architecture combining optical burst switching with dynamic wavelength allocation to achieve a guaranteed quality of service. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Burst aggregation is evaluated for a range of traffic statistics in terms of delay and packet loss rate, and an analytical model is given to quantify the benefits of dynamic wavelength reuse. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength-routed optical networks.The concept of optical burst switching (OBS) aims to allow access to optical bandwidth in dense wavelength division multiplexed (DWDM) networks at fractions of the optical line rate to improve bandwidth utilization efficiency. This paper studies a novel approach to combine OBS with dynamic wavelength allocation to provide a scalable optical architecture with a guaranteed QoS. In the proposed architecture all processing and buffering are concentrated at the network edge and bursts are assigned to fast tuneable lasers an routed over a bufferless optical transport core using dynamic wavelength assignment and no wavelength conversion. This guarantees forwarding with pre-defined delay at the edge, and latency due only to propagation time in the core. The edge burst aggregation mechanisms are evaluated for a range of traffic statistics to identify their impact on the allowable burst lengths, required buffer size and achievable edge delays. Bandwidth utilization and wavelength re-use are introduced and upper bounds for these parameters are derived to quantify the advantages of dynamic wavelength allocation, including the influence of the signaling round-trip time-required for lightpath reservation. The results allow evaluation of the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength-routed optical networks.

Timescale analysis for wavelength-routed optical burst-switched (WR-OBS) networks

The relationship of three timing parameters in the WR-OBS network architecture has been identified and investigated, to quantify the limits on the operation of a dynamic network. An adaptive burst assembler at the network edge provides an accurate estimation of the maximum edge delay whilst preventing buffer overflow, depending only on the mean and variance of incoming traffic. The round-trip time defines the achievable wavelength re-use under dynamic network operation, which could be as large as 20 for the example shown. The processing and queueing latency in the network control node links all three parameters and imposes a lower bound to the edge delay for a given number of edge routers. The unlimited burst size (UBS) scheme not only overcomes the main limitation of many OBS approaches-excessive burst loss for high network loads, but also reduces latency with increasing load, potentially ensuring adaptive network operation over a wide range of loads.

Analysis of burst scheduling for dynamic wavelength assignment in optical burst-switched networks

We discuss the benefits and limitations of the dynamic RWA in a centralised optical burst-switched network architecture. We present systematic comparison between the performance of the dynamic and static RWA in terms of QoS provisioning and bandwidth utilisation. Additionally, we consider a new component in the WROBS architecture, namely the request scheduler. We demonstrate that its application to the dynamic RWA significantly improves the performance of the WROBS.

Bandwidth Utilisation and Wavelength Re-Use in WDM Optical Burst-Switched Packet Networks

Results describing the design trade-offs in bandwidth utilisation and wavelength re-use in optical burst-switched networks are reported. The effects of traffic statistics are analysed, and a set of bounds for the network design and lightpath set-up time for dynamic network control is derived. The round-trip time required for signalling is identified to be a key parameter in optimising the network performance.

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.

Nanosecond channel-switching exact optical frequency synthesizer using an optical injection phase-locked loop (OIPLL)

Experimental results are reported on an optical frequency synthesizer for use in dynamic dense wavelength-division-multiplexing networks, based on a tuneable laser in an optical injection phase-locked loop for rapid wavelength locking. The source combines high stability (<1-kHz channel frequency error over 5-K temperature change), with high output power (/spl sim/2dBm), wide tuning range (40 nm), high spurious suppression (>50 dB), narrow linewidth (10 MHz), and fast wavelength switching (<10 ns).

Analysis of wavelength-routed optical burst-switched network performance

This paper studies a novel scalable network architecture combining optical burst switching (OBS) with dynamic wavelength allocation to guarantee quality of service (QoS), forming a wavelength-routed optical burst-switched network. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Different burst aggregation mechanisms are evaluated for a range of traffic statistics in terms of delay and packet loss rate. New network performance parameters in an analytical model quantify the advantages of dynamic wavelength allocation. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength routed optical networks.