Burst Assembly Research Articles

A Novel Contention Resolution Scheme for Optical Burst Switching Network

Optical burst switching (OBS) is a promised newly technology to implemented the all-optical transmission for Internet protocol (IP) traffic. How to effectively resolve the burst contention at the core router and propose a QoS (Quality of Service) supported burst assembly technique is a critical issue in nowadays. In this paper, a novel burst contention resolution scheme for OBS network has been proposed, this scheme based on two main aspects. Firstly, we propose a new burst segmentation approach named both-direction-segmentation (BDS), which could subtly take the advantages of burst head-segmentation and burst tail-segmentation approach. Secondly, corresponding to BDS, a novel burst assembly technique, which we called hybrid burst assembly (HBA) also has been proposed. Different from several existing burst assembly techniques, which only protect high-priority bursts. HBA has also been considered to protect the relatively high-class packets in low-priority bursts. A simulation is given out at the end of this paper, we observe that the proposed contention resolution scheme not only could minimize the losing of packets remarkably but also could efficiently and veritably support QoS for OBS network. The results have some valuable theoretic significances to design the real network in practice.

Effect of switching time on timer-based burst assembly and its effect on voice-over-Internet protocol quality of service over optical burst switching networks

It is well known that performance, such as burst loss probability and transmission delay, for optical burst switching (OBS) networks greatly depends on the switching time of the OBS switch. We analyze the switching-time effect on the burst loss probability using a continuous-time Markov chain. In our analysis, the transmission time of a burst is characterized with both the burst size and the switching time, and the burst loss probability, burst throughput, and data throughput are explicitly derived using the Geo,M/M/c/c queueing model. Numerical examples show that our analysis is quite useful for investigating the effect of the switching time on the timer-based burst assembly. We also consider voice-over-Internet Protocol (VoIP) service as a delay-sensitive application, and we investigate the switching time on the VoIP service. From our performance analysis, we derive an appropriate switching time and a burst processing time of the VoIP service in terms of the transmission distance.

Service differentiation using hybrid shared optical buffers in transparent optical networks

This paper proposes a novel service differentiation mechanism utilizing optical buffers in transparent optical networks. We first introduce fiber delay line (FDL)-based optical buffers and propose a hybrid shared optical buffered node. Based on the proposed buffer, diverse service requirements can be satisfied by assigning different priorities on accessing the buffer. Since the blocking performance is affected by the basic delay unit of FDL represented by a ratio of the burst length, this paper also takes into account the effect of the burst assembly process on the buffer performance. By dynamically adjusting the burst length under the changing traffic load, optimal performance of the proposed optical buffer can be achieved. Our simulation results show that diverse service requirements can be satisfied in terms of burst blocking probability and buffering delay time.

Dimensioning Burst Assembly Process in Optical Burst Switching Networks

Suitably aggregated data burst enhances link utilization and reduces data processing complexity of optical transport networks rather than just transmitting each bursty input traffic from access networks. This data burst generation method is called as a burst assembly process and has two assembly parameters, timer and threshold, for regulating burst release time and burst size. Since the traffic characteristics of data burst generated at the burst assembler may affect network performance, the decision of burst assembly parameters should be carefully designed. Thus, in this paper we study the dimensioning burst assembly process to find the burst assembly parameter values satisfying target performance. For this purpose, we first analyze timer-based and threshold-based burst assembly processes, respectively. As constraints on the dimensioning burst assembly process, we consider the following performance metrics: 1) processing delay of control packet, 2) burst loss at control plane, and 3) link utilization. Based on these constraints, a decision mechanism of the burst assembly parameters is proposed. From numerical analysis, we suggest a possible lower boundary value for the burst assembly parameters satisfying the target burst loss rate and delay time at the control plane.

Analysis of the Effects of Radiolytic-Gas Bubbles on the Operation of Solution Reactors for the Production of Medical Isotopes

One of the primary methods to produce medical isotopes, such as 99Mo, is by irradiation of uranium targets in heterogeneous reactors. Solution reactors present a potential alternative to produce medical isotopes. The Medical Isotope Production Reactor (MIPR) concept has been proposed to produce medical isotopes with lower uranium consumption and waste than those in heterogeneous reactors. Commercial production of medical isotopes in solution reactors requires steady-state operation at ~200 kW. At this power regime, fuel-solution temperature increase and radiolytic-gas bubble formation introduce a negative reactivity feedback that has to be mitigated. A model based on the point reactor kinetic equations has been developed to investigate these reactivity effects. This model has been validated against experimental results from the Los Alamos National Laboratory uranyl fluoride Solution High-Energy Burst Assembly (SHEBA) and shows the feasibility of solution reactors for the commercial production of medical isotopes.

Packet-based burst queue modeling at an edge in optical-burst switched networks

Optical burst switching is a promising solution for terabit transmission of IP data bursts over WDM networks as the next-generation Internet infrastructure. In this paper, we analyze burst queue with burst assembler at an edge in Optical Burst-Switched (OBS) networks. It is significant from the fact that most of processing and buffering are concentrated at the edge in OBS networks. Modeling the burst queue in terms of IP packets, we aim to investigate the waiting time in burst queue following burst assembler, the size of which influences the cost of constructing OBS networks. The proposed analytical model is verified through simulation.

Comparative Account of Bandwidth Efficiency in Optical Burst Switching and Optical Circuit Switching Networks

The performance of Optical Burst Switched (OBS) networks is compared to that of Optical Circuit Switched (OCS) networks in terms of bandwidth efficiency. Two traffic flow models are employed to investigate the effects of traffic grooming, packetization, buffering and burst assembly on bandwidth efficiency and utilization. Traffic is represented by fluid-flow continuous bit streams in the first model and by packet-based discrete flows in the second model. It is shown that the parameters of traffic characteristics and burst assembly have significant impact on the relative bandwidth savings of OBS. The bandwidth efficiency of OBS compared to OCS should not be taken for granted and has to be examined carefully on a case by case basis.

Amplification effects of the send rate of TCP connection through an optical burst switching network

This paper investigates support for TCP RENO flows in an Optical Burst Switching (OBS) network. In particular we evaluate the TCP send-rate, i.e., the amount of data sent per time unit taking into account the burst assembly mechanism at the edge nodes of the OBS network and burst loss events inside the network. The analysis demonstrates an interesting phenomenon, that we call correlation benefit. This phenomenon is introduced by the aggregation mechanism and can give rise, in some conditions, to a significant increase in the TCP send-rate. These results are obtained by means of an analytical model, based on a Markovian approach, and have been validated via an intensive simulation campaign.

Resource Allocation Algorithms for Controllable Service Differentiation in Optical Burst Switching Networks

Optical Burst Switching (OBS) has been developed as an efficient switching technique to exploit the capacity provided by Wavelength Division Multiplexing (WDM) transmission technology for the next generation optical Internet. One critical design issue in OBS is how to provide Quality-of-Service (QoS) on optical networks. In order to provide the service differentiation, we propose in this paper a buffer allocation algorithm to schedule bursts at the edge OBS nodes, a bandwidth allocation algorithm and a Fiber Delay Line (FDL) allocation algorithm to schedule bursts at the core OBS nodes. We also introduce a new burst assembly technique in which the burst is generated either when the sum of the collected packet sizes reaches the maximum threshold or when the burst assembling time reaches the timeout limit. Our simulation results show that the proposed algorithms achieve the controllable burst loss probability for different service classes. The bandwidth allocation algorithm performs very well at the core OBS nodes in terms of the low loss probability.

Throughput of high-speed TCP in optical burst switching networks

High-speed TCP (HSTCP) has been proposed to achieve high throughput in the high bandwidth and long-delay environment. The throughput of HSTCP is studied when the backbone network adopts the optical burst switching (OBS) technology. The study shows that small burst assembly time and a large burst loss ratio in OSB can reduce the throughput of HSTCP significantly, but HSTCP still performs much better than TCP.

Traffic Statistics and Performance Evaluation in Optical Burst Switched Networks

Optical burst switching (OBS) is a promising switching technology to exploit the potential benefits of optical communication and, at the same time, support statistical multiplexing of data traffic at a fine granularity. To quantify its benefits, the paper describes several typical burst assembly algorithms and studies their impact on the assembled burst traffic characteristics as well as the performance of TCP traffic. Also described is a proactive burst scheduling algorithm, called burst overlap reduction algorithm (BORA), which schedules locally assembled bursts in such a way as to reduce burst contention at downstream nodes in OBS networks. Furthermore, to provide analytical insights into performance evaluation of OBS networks, a burst loss model at an OBS node and its extension to different reservation protocols are presented.

A novel framework for IP DiffServ over optical burst switching networks

This paper presents a novel framework for IP Differentiated Services (DiffServ) over optical burst switching (OBS), namely, DS-OBS. The network architecture, functional model of edge nodes and core nodes, the control packet format, a novel burst, assembly scheme at ingress nodes and scheduling algorithm of core nodes are presented. The basic idea is to apply DiffServ capable burst assembly at ingress nodes and perform different per hop behavior (PHB) electronic treatments for control packets of different QoS class services at core nodes. Simulation results show that the proposed schemes can provide the best differentiated service for expedited forwarding (EF), assured forwarding (AF) and best, effort (BE) services in terms of end-to-end delay, throughput and IP packet loss probability.

Analysis of an Edge Router for Span-Constrained Optical Burst Switched (OBS) Networks

Edge routers are one of the key elements in an optical burst switched (OBS) network. Packets are assembled into bursts and then disassembled after being switched through the network. In a span-constrained OBS network, the edge router latency dominates propagation delay through the network. Consequently, the analysis of the edge router latency under different input traffic conditions and for different edge router parameters is essential for achieving an optimized network performance. In this paper, we present a framework to model and analyze in detail the performance of an edge router for span constrained networks under varying traffic utilizations, traffic statistics and burst assembly parameters. Two burst assembly algorithms are presented, and their impact on burst size and assembly time is studied for fixed and variable-size packets. We identify three distinct regions of edge router operation as a function of the input traffic statistics and burst assembly parameters. This enabled us to better understand the behavior of edge router latency under different input traffic conditions. The results of the analysis are then used to formulate design principles for the edge router. The impact of traffic self-similarity in each of these regions of operation was also analyzed. It is shown that self-similar traffic affects the variance of the burst size and assembly time, but does not impact overall edge router latency.

QoS Scheduler/Shaper for Optical Coarse Packet Switching IP-Over-WDM Networks

For IP-over-WDM networks, optical coarse packet switching (OCPS) has been proposed to circumvent optical packet switching limitations by using in-band-controlled per-burst switching and advocating traffic control enforcement to achieve high bandwidth utilization and quality-of-service (QoS). In this paper, we first introduce the OCPS paradigm. Significantly, we present a QoS-enhanced traffic control scheme exerted during packet aggregation at ingress nodes, aiming at providing delay and loss class differentiations for OCPS networks. Serving a dual purpose, the scheme is called (/spl psi/,/spl tau/)-Scheduler/Shaper, where /spl psi/ and /spl tau/ are the maximum burst size and burst assembly time, respectively. To provide delay class differentiation, for IP packet flows designated with delay-associated weights, (/spl psi/,/spl tau/)-Scheduler performs packet scheduling and assembly into bursts based on their weights and a virtual window of size /spl psi/. The guaranteed delay bound for each delay class is quantified via the formal specification of a stepwise service curve. To provide loss class differentiation, (/spl psi/,/spl tau/)-Shaper facilitates traffic shaping with larger burst sizes assigned to higher loss priority classes. To examine the shaping effect on loss performance, we analytically derive the departure process of (/spl psi/,/spl tau/)-Shaper. The aggregate packet arrivals are modeled as a two-state Markov modulated Bernoulli process (MMBP) with batch arrivals. Analytical results delineate that (/spl psi/,/spl tau/)-Shaper yields substantial reduction, proportional to the burst size, in the coefficient of variation of the burst interdeparture time. Furthermore, we conduct extensive simulations on a 24-node ARPANET network to draw packet loss comparisons between OCPS and just-enough-time (JET)-based OBS. Simulation results demonstrate that, through burst size adjustment, (/spl psi/,/spl tau/)-Shaper effectively achieves differentiation of loss classes. Essentially, compared to JET-based OBS using out-of-band control and offset-time-based QoS strategy, OCPS is shown to achieve invariably superior packet loss probability for a high-priority class, facilitating better differentiation of loss traffic classes.

Optical burst switching: a new area in optical networking research

In this tutorial, we give an introduction to optical burst switching and compare it with other existing optical switching paradigms. Basic burst assembly algorithms and their effect on assembled burst traffic characteristics are described first. Then a brief review of the early work on burst transmission is provided, followed by a description of a prevailing protocol for OBS networks called just-enough-time (JET). Algorithms used as an OBS core node for burst scheduling as well as contention resolution strategies are presented next. Trade-offs between their performance and implementation complexities are discussed. Recent work on QoS support, IP/WDM multicast, TCP performance in OBS networks, and labeled OBS is also described, and several open issues are mentioned.

On the Changes of Self-similar Traffic through Optical Burst-Switched Networks

The changes of self-similar traffic through an optical burst-switched network were completely investigated for the first time. The results showed that the burst assembly/ disassembly can change neither the self-similar nature of the traffic, nor the degree of self-similarity; they just change its short time-scale behaviors.

Photonic burst switching (pbs) architecture for hop and span-constrained optical networks

The paper presents a new architecture, called photonic burst switching (PBS), with variable time slot provisioning, supporting high-speed bursty data transmission within hop and span-constrained networks. First, the edge and switching node architecture for in-band and out-of-band signaling is defined with optical switch fabric performance parameters. Second, the edge router regions of operation for burst assembly are studied via simulations. Third, we introduce: (i) a GMPLS-based PBS software architecture in terms of control and data plane operations that is extended to enable the PBS optical interfaces with software building blocks for edge and switching nodes; (ii) an adaptive PBS MAC layer functionality and framing of multiple generic payloads. The integration of the proposed PBS network architecture with low-cost optical switching fabrics and GMPLS-based software architecture should provide the means for robust and efficient optical transport of bandwidth-demanding applications within enterprise networks.

Optimized TQ-MAP: An Adaptive Mapping Mechanism to Guarantee the Coherence of QoS Support from IP to OBS

Because of its scalability, the idea of coarse packet classification can be utilized to OBS networks. However, due to the limited number of priorities supported by OBS networks, we usually adopt a many-to-one composite class burst (CCB) assembly technique, e.g., N:1-CCB. In this kind of technique, there are two aspects related to scalable QoS support, i.e., mapping relationship and assembly resource allocation. This paper simultaneously takes the two aspects into consideration, and proposes a novel assembly mapping mechanism, called Optimized TQ-MAP, in which the most important feature is adaptivity. Based on nonlinear programming and differential calculus, it allocates the burst assembling capacity between classes fairly, efficiently and differentially, and matches IP QoS requirement with OBS QoS capacity as possible as it can. The simulation results show that Optimized TQ-MAP is more adaptive, and can efficiently guarantee the coherence of QoS support from IP to OBS.

A Novel Optical Burst Assembly Technique Based on a Dynamic Threshold Mechanism to Support Scalable QoS

In IP networks, coarse packet classification is a scalable QoS solution. Similarly, it can also be utilized to an OBS network. In order to match IP QoS requirements with the data processing capacity and flexibility of OBS networks, we propose a novel optical burst assembly technique, which is based on mapping rules and a dynamic threshold mechanism called ATQ-DT. How to map the IP QoS to burst priority is resolved by the mapping rules, and how to efficiently allocate the assembly capacity among classes belonging to the same priority is answered by ATQ-DT. This mechanism determines the maximum share for each class, which is proportional to the current unused capacity. Among the three mapping rules we propose, TQ-MAP is the most reasonable one because it considers both the traffic condition and the QoS requirement. As shown by simulation results, the assembly technique ATQ-DT with TQ-MAP can most remarkably improve the packets loss probability (PLP) to support QoS.

A Data Burst Assembly Algorithm in Optical Burst Switching Networks

Presently, optical burst switching (OBS) technology is under study as a promising solution for the backbone of the optical Internet in the near future because OBS eliminates the optical buffer problem at the switching node with the help of no optical/electro/optical conversion and guarantees class of service without any buffering. To implement the OBS network, there are a lot of challenging issues to be solved. The edge router, burst offset time management, and burst assembly mechanism are critical issues. In addition, the core router needs data burst and control header packet scheduling, a protection and restoration mechanism, and a contention resolution scheme. In this paper, we focus on the burst assembly mechanism. We present a novel data burst generation algorithm that uses hysteresis characteristics in the queueing model for the ingress edge node in optical burst switching networks. Simulation with Poisson and self-similar traffic models shows that this algorithm adaptively changes the data burst size according to the offered load and offers high average data burst utilization with a lower timer operation. It also reduces the possibility of a continuous blocking problem in the bandwidth reservation request, limits the maximum queueing delay, and minimizes the required burst size by lifting up data burst utilization for bursty input IP traffic.