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1.
In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. To prevent packet loss in the switch, fiber delay lines (FDLs) are used as optical buffers to store optical packets. However, assigning FDLs to the arrival packets to achieve high throughput, low delay, and low loss rate is not a trivial task. In the authors' companion paper, several efficient scheduling algorithms were proposed for single-stage shared-FDL optical packet switches (OPSs). To further enhance the switch's scalability, this work was extended to a multistage case. In this paper, two scheduling algorithms are proposed: 1) sequential FDL assignment and 2) multicell FDL assignment algorithms for a three-stage optical Clos-Network switch (OCNS). The paper shows by simulation that a three-stage OCNS with these FDL assignment algorithms can achieve satisfactory performance. 相似文献
2.
Packet contention is a major issue in an optical packet switching network. It is not a trivial task to resolve contention
due to lack of optical RAM technology. This article proposes a two-stage shared fiber delay line (FDL) optical packet switch
for contention resolution. In this article, shared FDLs are used to buffer optical packets, in which a pool of buffer memory
is shared among all switch output ports. Most of the existing optical buffering schemes are output-based which require a huge
number of FDLs as well as a larger switch size that incur extra implementation cost. However, a shared buffering approach
is considered in this article in order to reduce implementation cost. In this article, FDLs are implemented in two stages
using an extremely simple auxiliary switch. The proposed switch architecture leads to more efficient use of buffer space.
The superiority of the proposed switch architecture has been established by means of extensive simulations. The performance
of the proposed switch is investigated under bursty traffic. Simulation result shows that the proposed switch can achieve
satisfactory performance at the price of a reasonable amount of FDLs. Moreover, the significance of the proposed switch is
confirmed by simulation. 相似文献
3.
Jianming Liu Lee T.T. Xiaohong Jiang Horiguchi S. 《Lightwave Technology, Journal of》2009,27(8):955-966
Buffers are essential components of any packet switch for resolving contentions among arriving packets. Currently, optical buffers are composed of fiber delay lines (FDL), whose blocking and delay behavior differ drastically from that of conventional RAM at least two-fold: 1) only multiples of discrete time delays can be offered to arriving packets; 2) a packet must be dropped if the maximum delay provided by optical buffer is not sufficient to avoid contention, this property is called balking. As a result, optical buffers only have finite time resolution, which may lead to excess load and prolong the packet delay. In this paper, a novel queueing model of optical buffer is proposed, and the closed-form expressions of blocking probability and mean delay are derived to explore the tradeoff between buffer performance and system parameters, such as the length of the optical buffer, the time granularity of FDLs, and to evaluate the overall impact of packet length distribution on the buffer performance. 相似文献
4.
In this paper, a novel optical packet switch is proposed, which uses a set of shared fiber delay lines (FDLs) and a set of
shared tunable wavelength converters (TWCs) to resolve optical packet contentions. In addition, two control algorithms, i.e.,
Fiber-First (FF) and Wavelength-First (WF), are proposed to schedule optical packets. Performance of the novel switch is evaluated
by means of simulation experiments. Simulation results show that based on either of these two control algorithms, the switch
can achieve super performance without employing a lot of FDLs and TWCs. Moreover, the performance of FF and WF is compared.
Detail analyses are also given in this paper. 相似文献
5.
Tao Zhang 《International Journal of Communication Systems》2012,25(2):158-168
A major challenge in packet‐based optical networks is packet contention, which occurs when two or more packets are heading to the same output at the same time. To resolve contention in the optical domain, a fundamental approach is fiber delay‐line (FDL) buffering, in which packets can be delayed for a fixed amount of time. In the literature, the performance of FDL buffering has been studied extensively. However, most existing works are based on an assumption that there is only one fiber per link in the network. In this paper, we address the architecture and performance of FDL buffers in packet‐based asynchronous multifiber optical networks (PAMFONET), in which each link in the network may consist of multiple optical fibers. We propose a framework for FDL buffers in PAMFONET, in which we provide three essential architectures and corresponding packet scheduling policies. Extensive simulation results show that, with appropriate settings, the same number of FDLs can lead to better performance in multifiber networks than in single‐fiber networks. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
Zheng Liang Shilin Xiao 《Lightwave Technology, Journal of》2007,25(8):1978-1985
The fiber delay line (FDL) buffer is widely used in optical packet switching networks for contention solution. In this paper, a quantized delay buffer model is proposed to analyze the performance of the single-wavelength FDL buffer. Considering the delay quantization in the FDLs, the delay time and the waiting time of the packet are discussed. Without specific assumptions of the packet arrival process and length distribution, the model presents a generic approach to study the delay time distribution and modify the integral equation for the waiting time distribution. Analytic and exact results of the two aforementioned distributions can be obtained without any approximation. The accuracy of the model is validated through simulation. 相似文献
7.
Performance of fiber delay‐line buffers in asynchronous packet‐based optical switching networks with wavelength conversion
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A major challenge in asynchronous packet‐based optical networks is packet contention, which occurs when two or more packets head to the same output at the same time. To resolve contention in the optical domain, two primary approaches are wavelength conversion and fiber delay line (FDL) buffering. In wavelength conversion, a contending packet can be converted from one wavelength to another in order to avoid conflict. In FDL buffering, contending packets can be delayed for a fixed amount of time. While the performance of wavelength conversion and FDL buffering has been evaluated extensively in synchronous networks with fixed‐sized packets, in this paper, we study the performance of FDL buffers in asynchronous packet‐based optical networks with wavelength conversion. An analytical model is proposed to evaluate the performance in terms of packet loss probability and average delay. Extensive simulation and analytical results show that, with appropriate settings, FDL buffers can perform much better in switches with wavelength conversion than in switches with no conversion. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
Optical packet switching (OPS) is a promising technology to enable next-generation high-speed IP networks. A major issue in
OPS is packet contention that occurs when two or more packets attempt to access the same output fiber. In such a case, packets
may be dropped, leading to degraded overall switching performance. Several contention resolution techniques have been investigated
in the literature including the use of fiber delay lines (FDLs), wavelength converters (WCs), and deflection routing. These
solution typically induce extra complexity to the switch design. Accordingly, a key design objective for OPS is to reduce
packet loss without increasing switching complexity and delay. In this paper, we investigate the performance of contention
resolution in asynchronous OPS architectures with shared FDLs and WCs in terms of packet loss and average switching delay.
In particular, an enhanced FDL-based and a novel Hybrid architecture with shared FLDs and WCs are proposed, and their packet scheduling algorithms are presented and evaluated. Extensive
simulation studies show that the performance of proposed FDL-based architecture outperforms typical OPS architectures reported
in the literature. In addition, it shown that, for the same packet loss ratio, the proposed hybrid architecture can achieve
up to 30% reduction in the total number of ports and around 80% reduction in the overall length of fiber as compared to the
FDL-based architectures. 相似文献
9.
Efficient burst scheduling algorithms in optical burst-switched networks using geometric techniques 总被引:4,自引:0,他引:4
Jinhui Xu Chunming Qiao Li J. Guang Xu 《Selected Areas in Communications, IEEE Journal on》2004,22(9):1796-1811
Optical burst switching (OBS) is a promising paradigm for the next-generation Internet. In OBS, a key problem is to schedule bursts on wavelength channels, whose bandwidth may become fragmented with the so-called void (or idle) intervals, using both fast and bandwidth efficient algorithms so as to reduce burst loss. To date, two well-known scheduling algorithms, called Horizon and LAUC-VF, have been proposed in the literature, which trade off bandwidth efficiency for fast running time and vice versa, respectively. In this paper, we propose a set of novel burst scheduling algorithms for OBS networks with and without fiber delay lines (FDLs) utilizing the techniques from computational geometry. In networks without FDLs, our proposed minimum-starting-void (Min-SV) algorithm can schedule a burst in O(logm) time, where m is the total number of void intervals, as long as there is a suitable void interval. Simulation results suggest that our algorithm achieves a loss rate which is at least as low as LAUC-VF, but can run much faster. In fact, its speed can be almost the same as Horizon (which has a much higher loss rate). In networks with FDLs, our proposed batching FDL algorithm considers a batch of FDLs to find a suitable FDL to delay a burst which would otherwise be discarded due to contention, instead of considering the FDLs one by one. The average running time of this algorithm is therefore significantly reduced from that of the existing burst scheduling algorithms. Our algorithms can also be used as algorithmic tools to speed up the scheduling time of many other void-filling scheduling algorithms. 相似文献
10.
Yusuke Hirota Shinya Yatsuo Hideki Tode Koso Murakami 《Optical Switching and Networking》2012,9(3):252-263
Programmable variable delay lines have been developed, so as to delay packets in variable durations by combining several lengths of Fiber Delay Lines (FDLs) in optical packet switch. In practice, Two-stage variable optical packet switch with this programmable variable delay lines has been proposed. This switch has two buffers. The one is the programmable variable delay lines (Look-ahead Buffer). The other is the fixed FDLs that re-input a packet from the output to the input (Loop-back Buffer). The switch can foresee following packets and avoid contentions effectively by using two buffers. However, existing studies only focus on the Look-ahead Buffer. Intelligent usage of the Loop-back Buffer is actually out of concern. This paper proposes a sophisticated scheduling method in the Two-stage switch. The proposed method controls both the Look-ahead Buffer and the Loop-back Buffer cooperatively and improves the utilization of the switching process. The proposed method uses the Loop-back Buffer adaptively and distributes traffics in time and space domain. The effectiveness of the proposed method is evaluated through extended simulation experiments and basic hardware design. 相似文献
11.
Develder Chris Houdt Benny Van Blondia Chris Pickavet Mario Demeester Piet 《Photonic Network Communications》2004,8(2):149-161
The major goal of optical packet switching (OPS) is to match switching technology to the huge capacities provided by (D)WDM. A crucial issue in packet switched networks is the avoidance of packet losses stemming from contention. In OPS, contention can be solved using a combination of exploitation of the wavelength domain (through wavelength conversion) and buffering. To provide optical buffering, fiber delay lines (FDLs) are used. In this paper, we focus on an optical packet switch with recirculating FDL buffers and wavelength converters. We introduce the Markovian arrival process with marked transitions (MMAP), which has very desirable properties as a traffic model for OPS performance assessment. Using this model, we determine lower and upper bounds for the packet loss rate (PLR) achieved by the aforementioned switch. The calculation of the PLR bounds through matrix analytical methods is repeated for a wide range of traffic conditions, including highly non-uniform traffic, both in space (i.e., packet destinations) and time (bursty traffic). The quality of these bounds is verified through comparison with simulation results. 相似文献
12.
An analytical model is derived to evaluate the performance of an optical switch using a feed-forward fiber delay line (FDL)
per output for contention resolution. Two different forwarding algorithms for the switch are presented and evaluated: a simple
forwarding algorithm (SFA) that is easier to implement, and an enhanced algorithm that provides better performance in terms
of both packet loss probability and packet delay. The analytical model can be utilized with both packet and burst switching
schemes to characterize the performance of the proposed architecture. Results show that the proposed architecture reduces
the packet loss probability compared to that without FDLs. Finally, the same architecture is shown to be capable of supporting
Quality of Service (QOS).
相似文献
Anura Jayasumana (Corresponding author)Email: |
13.
Signal loss and noise accumulation can cause fading in optical buffers implemented by fiber delay lines (FDLs). Optical packets that excessively recirculate through FDLs are easily dropped from their routing paths. Therefore, analytical models and packet scheduling schemes require additional considerations for FDL buffers. This work proposes an analytical model for all-optical packet switching networks with finite FDL buffers and a general class of scheduling schemes including many basic scheduling schemes. We intend to minimize the packet loss probability by ranking packets to achieve an optimal balance between latency and residual lifetime in the general class of scheduling schemes. The analytical model is based on a non-homogeneous Markovian analysis to study the effects of various scheduling schemes on packet loss probability and average latency. Analytical results show how various network parameters affect the optimal balance, and illustrate how properly balancing latency and residual distance can significantly improve network performance. 相似文献
14.
《Photonics Technology Letters, IEEE》2008,20(18):1581-1583
15.
Mounire El Houmaidi Mostafa A. Bassiouni Guifang Li 《Photonic Network Communications》2007,13(1):111-122
In this paper, we combine fiber delay lines (FDL) and optical wavelength conversion (OWC) as the solution for the burst contention problem in optical burst switching (OBS). We present a placement algorithm, k-WDS, for the sparse placement of FDLs at a set of selected nodes in the network. The algorithm can handle both uniform and non-uniform traffic patterns. Our extensive performance tests show that k-WDS provides more efficient placement of optical fiber delay lines than the well-known approach of placing the resources at nodes with the highest experienced burst loss. Performance results are also given to compare the benefit of using FDLs alone, OWCs alone, as well as a mixture of both FDLs and OWCs. A new algorithm, A-WDS, for the placement of an arbitrary numbers of FDLs and OWCs is presented and evaluated under different uniform and non-uniform traffic loads using network simulation of the NSFNET topology and randomly generated graphs. The paper is concluded by presenting the design of a cost-effective optical switch equipped with variable-delay FDL bank. Based on the switch design, a scheme to provide differentiated services for multiple classes of traffic is presented and evaluated. 相似文献
16.
Scheduling Algorithms for a Slotted Packet Switch with either Fixed or Variable Length Packets 总被引:3,自引:2,他引:1
Callegati F. Cerroni W. Corazza G. Develder C. Pickavet M. Demeester P. 《Photonic Network Communications》2004,8(2):163-176
We address the problem of congestion resolution in optical packet switching (OPS). We consider a fairly generic all-optical packet switch architecture with a feedback optical buffer constituted of fiber delay lines (FDL). Two alternatives of switching granularity are addressed for a switch operating in a slotted transfer mode: switching at the slot level (i.e., fixed length packets of a single slot) or at the burst level (variable length packets that are integer multiples of the slot length). For both cases, we show that in spite of the limited queuing resources, acceptable performance in terms of packet loss can be achieved for reasonable hardware resources with an appropriate design of the time/wavelength scheduling algorithms. Depending on the switching units (slots or bursts), an adapted scheduling algorithm needs to be deployed to exploit the bandwidth and buffer resources most efficiently. 相似文献
17.
18.
We present an exact analytical model for single-wavelength quality of service (QoS) differentiation in a two-class optical packet switch. In this system, QoS differentiation is achieved by limiting the set of fiber delay lines (FDLs) to the low-priority class, whereas the high-priority class is allowed to access the entire FDL bank. The analytical model is based on multi-regime Markov fluid queues and is extensible to multi-class systems with more than two classes. Markovian arrival process packet arrivals and phase-type distributed packet sizes are considered for the purpose of generality. The proposed analytical model is validated through simulations. The numerical results provide insight into determining appropriate subsets of FDLs allowed for the access of the low-priority class. The results also show that it is possible to direct almost all the packet losses to the low-priority class under moderate loads. 相似文献
19.
W. Rogiest K. Laevens D. Fiems H. Bruneel 《AEUE-International Journal of Electronics and Communications》2010,64(10):953-959
Circumventing the speed bottleneck of electronic switching, novel switching approaches like optical burst switching (OBS) and optical packet switching (OPS) handle the switching of bursts (or packets) in backbone nodes optically, and include a set of fiber delay lines (FDLs) for optical buffering. While previous work acknowledges the performance difference between optical FDL buffers and electronic RAM buffers, the important role of synchronization herein has received little attention to date. 相似文献
20.
Optical buffers implemented by fiber delay lines (FDLs) have a volatile nature due to signal loss and noise accumulation.
Packets suffer from excessive recirculation through FDLs, and they may be dropped eventually in their routing paths. Because
of this, packet scheduling becomes more difficult in FDL buffers than in RAM buffers, and requires additional design considerations
for reducing packet loss. We propose a latency-aware scheduling scheme and an analytical model for all-optical packet switching
networks with FDL buffers. The latency-aware scheduling scheme is intended to minimize the packet loss rate of the networks
by ranking packets in the optimal balance between latency and residual distance. The analytical model is based on non-homogeneous
Markovian analysis to study the effect of the proposed scheduling scheme on packet loss rate and average delay. Furthermore,
our numerical results show how various network parameters affect the optimal balance. We demonstrate quantitatively how to
achieve the proper balance between latency and residual distance so that the network performance can be improved significantly.
For instance, we find that under a given latency limit and light traffic load our scheduling scheme achieves a packet loss
rate 71% lower than a scheduling scheme that ranks packets simply based on latency. 相似文献