A cost-effective approach to optical packet/burst scheduling (original) (raw)
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A QoS supporting scheduling algorithm for optical burst switching DWDM networks
GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270)
The ubiquity of IP has led to IP-over-WDM as the core architecture for the next-generation optical Internet. Optical Burst Switching(OBS) has been proposed to be a competitive switching technology for DWDM networks. Data channel scheduling Algorithm is one of the major challenges in OBS. The same-service-to-all model of the current Internet is inadequate for the diverse quality of service expectations of Internet applications and users. Differentiated Service (DiffServ) was proposed to provide a scalable and manageble architecture for service differentiation in IP networks. This paper proposes a scheduling algorithm based on an existing LAUC-VF algorithm to support DiffServ and takes advantage of MPLS. Simulation results demonstrate that this algorithm has better QoS performance than the existing LAUC-VF algorithm.
Fast and versatile scheduler design for optical packet/burst switching
Optical Switching and Networking, 2011
The most promising solutions to increase bandwidth efficiency in IP over DWDM networks are represented by Optical Packet and Burst Switching. Due to the statistical multiplexing approach adopted, these paradigms must deal with packet/burst contentions at the node output channels and require the use of scheduling algorithms to optimize resource assignment and bandwidth utilization. However, very strict time constraints on the scheduling operations are imposed by the extremely high bit rates used, making the actual feasibility of the scheduler control logic a major implementation issue common to both technologies. This paper provides a specific formulation of the scheduling problem that can be used as the basis for the practical design of a fast and versatile scheduler, capable of implementing many algorithms found in literature. A possible implementation of the scheduler sub-functions, mainly based on the use of combinatorial operations, is also discussed and supported by the simulation of the hardware implementation time response, with results that demonstrate the feasibility of the proposed solution.
Optimal Burst Scheduling in Optical Burst Switched Networks
Journal of Lightwave Technology, 2000
Optical burst switching (OBS) is an emerging technology that allows variable size data bursts to be transported directly over dense wavelength division multiplexing links. In order to make OBS a viable solution, the burst-scheduling algorithms need to be able to utilize the available wavelengths efficiently, while being able to operate fast enough to keep up with the burst incoming rate. For example, for a 16-port OBS router with 64 wavelengths per link, each operating at 10 Gb/s, we need to process one burst request every 78 ns in order to support an average burst length of 100 kB. When implemented in hardware, the well-known horizon scheduler has O(1) runtime for a practical number of wavelengths. Unfortunately, horizon scheduling cannot utilize the voids created by previously scheduled bursts, resulting in low bandwidth utilization. To date, minimum starting void is the fastest scheduling algorithm that can schedule wavelengths efficiently. However, while its complexity is O(log m), it requires 10 log m memory accesses to schedule a single burst. This means that it can take up to several microseconds for each burst request, which is still too slow to make it a practical solution for OBS deployment. In this paper, we propose an optimal burst scheduler using constant time burst resequencing (CTBR), which has O(1) runtime. The proposed CTBR scheduler is able to produce optimal burst schedules while having processing speed comparable to the horizon scheduler. The algorithm is well suited to highperformance hardware implementation.
Optical burst switching is a promising solution for terabit transmission of IP data bursts over WDM networks. Optical Burst Switching (OBS) is a promising paradigm for the next-generation Internet. In this paper, we propose a random algorithm, first-fit wavelength algorithm and wavelength reservation algorithm. The blocking probability of the Optical Burst Switch will be analyzed depending upon the number of channels, loads and the number of links. The number of wavelengths on all the links will be kept constant. The blocking probability of the proposed scheme is significantly reduced as compare with general OBS.
Efficient resource reservation for optical burst switching networks
2009 IEEE Global Telecommunications Conference, GLOBECOM 2009
Optical burst switching (OBS) is one promising method for data transfer in photonic networks based on a WDM (Wavelength Division Multiplexing) technology. In the OBS scheme, the wavelength is exclusively reserved along the source and destination nodes, when the burst data is generated at the source. Then, efficient data transfer is expected. However, its performance is heavily dependent on the number of links that the lightpath goes through. TCP-based applications account for a majority of data traffic in the Internet; thus understanding and improving the performance of TCP over OBS networks is critical. In this paper, we present a new parallel wavelength reservation method for optical burst switching (OBS) networks based on adapting the set of potential wavelengths with the number of hops in the path. The uniqueness of this work when compared to existing works is that buffering resources, which consist of Optical Delay Lines (ODLs), are considered in the reservation mechanism. The consequence of this is that the time made by the segments in the various buffers across the selected path is taken into consideration. Various simulation experiments have been conducted to evaluate the performance of the scheme. It is found that our approach has better performance than previous related works reported in the literature. http://ieeexplore.ieee.org/xpls/abs\_all.jsp?arnumber=5425688
Techniques for improved scheduling in optical burst switched networks
2009 International Symposium on Autonomous Decentralized Systems, 2009
Optical burst switching (OBS) has emerged as a viable switching alternative in backbone optical networks since it can support high data rates with an intermediate granularity compared to wavelength routing and optical packet switching. At the edges of an OBS cloud, packets are assembled to form bursts which enter the network core and are switched on the fly using bandwidth previously reserved by their control packets at each node. A key problem in OBS networks is the assignment of wavelengths to incoming bursts, i.e. the scheduling of bursts. This paper proposes two new techniques which are shown to improve burst scheduling algorithms by lowering their complexity. The first proposed technique is based on a triangular estimator that defines a "drop zone"; bursts that fall into this area are considered to have a very low probability of finding a suitable wavelength and as such, no effort is made to schedule them. According to the second approach, the drop zone is defined dynamically based on the burst drop history. Simulation results show that both approaches yield burst drop rates marginally higher or identical to the LAUC-VF scheduling algorithm while reducing the number of channel or void checks and thus the algorithm complexity and execution time.
On ordered scheduling for optical burst switching
Computer Networks, 2005
Optical burst switching (OBS) is a promising optical networking paradigm for efficient transport of bursty IP traffic over wavelength division multiplexing (WDM) optical Internet networks. In OBS, the header of a burst is sent in advance of the data burst to reserve a wavelength channel at each optical switching node along the path. The nodes use a scheduling algorithm to assign wavelengths to incoming bursts. Our work is motivated from the observation that existing scheduling algorithms assign a wavelength to a burst when its header arrives at the node. Thus, information about other bursts whose headers arrive later is not available when the scheduling decision is made. This leads to suboptimal scheduling decisions and unnecessary burst dropping. The key idea in our proposed algorithm, Ordered Scheduling, is to defer making the scheduling decision until just before the burst arrival in order to have full knowledge about other bursts. The effectiveness of the proposed algorithm is studied through simulation and the computational complexity and signalling overhead are analysed.
Photonic Network Communications, 2005
Optical burst switching (OBS) is emerging as one promising switching paradigm for the next generation optical networks. To support multiple services in burst-switching networks, the OBS paradigm should support some quality-of-service (QoS) provisioning. A major design issue in such networks is to reduce the blocking probability of the bursts arising due to resource contention at the intermediate core router. In this paper, we propose a signaling protocol which we call 'Delayon-Demand' (OBS-DoD), to reduce blocking probability and support QoS in optical burst-switching networks. The proposed scheme guarantees that at least one of the bursts succeeds depending on its priority, propagation delay from the ingress router, and the burst-size when contention occurs at the core router. For this, we use a control packet to delay, in case of a contention, the transmission of bursts at the ingress router. We compare the performance of our proposal, by simulation, with an earlier proposed scheme, and show that the proposed OBS-DoD outperforms the earlier scheme in reducing the blocking probability. For simulation, we generated bursty traffic using an M/Pareto distribution http://dx.
Efficient techniques for improved QoS performance in WDM optical burst switched networks
Computer Communications, 2005
In this paper, we address the problems of burst scheduling, network fairness, and service differentiation in wavelength division multiplexing (WDM) optical burst switched (OBS) networks. We propose two approaches-time-slotting and burst fragmentation-to provide efficient solutions for the above problems. We also propose a path selection algorithm to distribute label switched paths (LSP) based on load balancing. Time slotting refers to the quantization of time into slots of fixed sizes. Time slotting aids fast implementation of scheduling algorithms. Further, the slotting is local to the nodes and they need not be synchronized across the network. In burst fragmentation, a burst is fragmented instead of being dropped if it cannot be accommodated on any wavelength as a whole. These fragments are then sent on different wavelengths on the same path. Only in the event, that a fragment cannot be scheduled on any wavelength of the link, is the burst dropped. We develop a new scheduling algorithm based on time-slotting and fragmentation. This algorithm has several attractive features such as fast and simple implementation and improved burst dropping performance. Using the hop-based shortest path algorithm to route a burst without accounting for the link load results in poor burst dropping performance. This is because, some links could be heavily loaded forming a bottleneck for network performance. Load balancing approach aims at reducing the bottleneck of data traffic in the network. We develop a path selection algorithm based on load balancing with the objectives of improving network performance in terms of burst dropping probability and improve fairness among bursts traversing paths of different lengths. We then develop an offset-based algorithm to provide inter-class service differentiation and intra-class fairness for the bursts belonging to classes with different levels of priority. An attractive feature of this algorithm is that it works with a constraint of maximum permissible initial offset time in order to reduce the burst transfer delay and also to reduce the buffer requirements at the ingress edge routers. It also ensures that shorter-hop bursts of a low-priority class does not perform better than the longer-hop bursts belonging to a high-priority class. Extensive simulation results have been used to demonstrate the effectiveness of the proposed approaches and algorithms for various identical and non-identical traffic demand scenarios. q
A Review of Optical Burst Switching in Wavelength Division Multiplexing Networks
2014 International Conference on Information Technology, 2014
Optical Burst Switching (OBS) is considered as an efficient switching paradigm for building the next generation optical Internet. This review has been motivated by the need for techniques that are capable of supporting the future bandwidth requirement of next-generation applications and services of Internet Protocol (IP) networks. The authors have discussed the basic concepts of OBS paradigm and outlined the signaling and scheduling issues related to OBS networks. Further, a brief summary on the issues that are essential for provisioning Qualityof-Service (QoS) in OBS networks has been outlined. Finally, an analytical model is presented to provide Burst Loss Probability (BLP) guarantees between every pair of source-destination nodes in the network.