This paper motivates the combination of optical burst switching (OBS) networks with wavelength-routed networks which provide a virtual topology. Opportunities for advanced network design, support for important future transport network scenarios, and resilience as well as capacity adaptation functionality are among its key benefits. The paper discusses principal trade-offs, both qualitatively and quantitatively, regarding virtual topologies and statistical multiplexing in order to derive guidelines for resource efficient topology design. Then, the OBTN architecture is described, which can efficiently transport burst data over a virtual topology of lightpaths and can reduce the port count of optical burst-switched nodes. Finally, the OBTN dimensioning process is outlined and results of a unified performance and cost comparison are presented.
This paper presents an architecture and a realization of a burst reservation module for optical burst switching using the just-enough-time (JET) reservation scheme. JET is a reserve-a-fixed-duration reservation algorithm, i.e., wavelength channels are allocated exactly for the burst transmission time. As the exact start and end times of all bursts have to be recorded and processed for JET burst reservation, several publications assumed its realization to be prohibitively complex. This paper proposes an architecture for a hardware-based reservation module for JET. This architecture has been described in VHDL and synthesized on an FPGA representative for today's programmable logic technology. The proposed solution is evaluated under dynamic traffic based on timing and resource utilization results taken from the FPGA realization. The results of the performance evaluation prove that with this reservation module JET can even be realized for burst durations in the microsecond range.
Optical burst switching (OBS) has been proposed in the late 1990s as a novel photonic network architecture directed towards efficient transport of IP traffic. OBS aims at cost-efficient and dynamic provisioning of sub-wavelength granularity by optimally combining electronics and optics. Optical bursts cut through intermediate nodes, i.e., data stays in the optical domain at all times, while the control information is signaled out-of-band and processed electronically. In contrast to optical packet switching, OBS aggregates and assembles packets electronically into bursts of variable length according to destination and QoS class at the edge of the network. This paper surveys current trends in OBS and discusses proposed solutions for burst reservation and scheduling, burst assembly, contention resolution and QoS provisioning as well as design and scalability of OBS nodes. Also, it looks at the question of the optimal burst size, which has been around from the very beginning of OBS, based on recent trends and results. On the one hand, burst size and burst characteristics are influenced by client layer traffic and burst assembly scheme. On the other hand burst size and burst characteristics have an impact on network performance and node architectures. Finally, consequences of burst durations in the microsecond and millisecond range are presented and compared.
Optical burst switching (OBS) has recently attracted increasing interest
as a network architecture for the future optical Internet.
In OBS, efficient contention resolution is a key issue.
This paper investigates the performance of shared converter
pools for contention resolution in OBS.
First, key design parameters for contention resolution
in OBS nodes which employ wavelength converters and
simple fiber delay line (FDL) buffers are discussed.
Then, the performance of a converter pool is evaluated
for a Poisson and
a self-similar traffic model.
Depending on load and node dimensioning, the number of wavelength converters
can be reduced by 50-75%.
Finally, different converter usage strategies for the combination of
a converter pool and an FDL buffer are presented and compared.
A strategy that prefers FDL's over converters for contention resolution
can reduce burst loss probability
for converter pools with a small number of converters.
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