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1.
为了降低光突发交换网络中突发包的丢失率、减小网络延时、提高网络信道的利用率,采用了一种新型考虑优先级的基于冗余合并的突发包冲突解决机制。算法增加了回退信道作为保护信道,根据业务的优先级对冲突的突发包进行分段,使无法顺利传送的突发包碎片进入到回退信道;同时,考虑到网络中存在着很多短小而难以利用的信道资源,算法将回退信道里的突发包碎片进行多次克隆,多个克隆碎片和由上游节点到来的突发包合并成粒度可变的虚拟突发包发送,克隆碎片的优先级定义为最低,以保证不抢占正常突发包的信道资源。结果表明,相比以往的冲突解决算法,此算法具有较低的丢包率、相对小的延时率和优越的信道利用率。 相似文献
2.
A fundamental issue in optical burst switching (OBS) networks is to solve the burst contention for the core node. In this
paper, a novel priority-based contention solution strategy for OBS networks is proposed. When the contention occurs, the burst
priority is considered firstly, and then the burst segmentation method is used for the low priority bursts in this strategy.
Ensuring the integrity of high priority bursts, part of the segmented bursts can be transmitted to the destination node via
combining wavelength conversion and optical buffer method. Simulation results show that the proposed scheme not only ensures
the integrity of high priority bursts, but also reduces the packet loss rate of the low priority bursts maximally, so that
it can support good quality of service (QoS) for the network. 相似文献
3.
Network dimensioning should be progressed for pursuing the ultimate efficiency of network system resources in order to satisfy
target performance. This article studies node dimensioning as a method of resource optimization in optical burst switching
(OBS) networks. OBS is a new switching technology for pursuing bufferless transparent optical networks by sending control
packets prior to data burst in order to provision resources for the burst. However, the basic assumption of a bufferless node
implies burst contention at a core node when more than two bursts attempt to move forward the same output simultaneously.
Thus, burst contention is a critical performance metric and this article takes it into account as a constraint on node dimensioning
and target performance. In this article, we first present node dimensioning issues for OBS networks. Two constraints from
the transport plane and the control plane which affect burst contention are then introduced. The effect of the burst assembly
process on node dimensioning is also presented. From numerical analysis, the optimal number of wavelengths in a link, which
provides the lowest blocking probability, is obtained to suggest a guideline for node dimensioning. 相似文献
4.
为了降低光突发交换网络中突发包的丢失率、降低网络路径的阻塞率、减小突发包冲突的概率,提出了考虑优先级的突发包碎片可控合并重传算法。当网络中数据通信发生冲突时,该算法能根据优先级进行突发包的分片,核心节点将这一信息反馈给边缘节点,边缘节点根据突发碎片的优先级以一定的概率重传被丢弃的突发包分片;同时,针对由于多次重传导致的突发包碎片过多的问题,该算法还按照突发包碎片的优先级顺序进行碎片重组,大大降低了网络的阻塞率。结果表明,相比以往的冲突解决算法,此算法在网络业务繁忙时的数据丢比特率和网络阻塞率方面的改善作用有比较明显的优势。这一结果对光突发交换网络的网络的性能改善方面是有帮助的。 相似文献
5.
OBS网络中一种基于突发包优先级分割的可控重传方案 总被引:2,自引:2,他引:0
在光突发交换(OBS)网络中,突发包会由于竞争OBS核心节点输出端口的有限波长资源而发生冲突。突发包重传能够在一定程度上减少由于突发包在核心节点冲突而导致的数据损失,但重传次数的增加可能会加重网络负荷,反而增加数据丢失率。并且,在多业务存在的OBS网络中,重传方案需要能够实现区分服务以保证网络的服务质量(QoS)。据此,本文提出一种基于突发包优先级分割的可控重传方案,在实施优先级分割的同时,根据网络负荷赋予每次重传不同的概率,并对重传次数加以控制。最后,仿真分析了路径阻塞率和不同优先级业务的字节丢失率(ByLP,byte loss probability)性能。 相似文献
6.
7.
Li-Mei Peng Kyoung-Min Yoo Kyeong-Eun Han Young-Chon Kim 《Photonic Network Communications》2008,15(3):213-225
Optical burst switching (OBS) has been proposed as a new optical switching paradigm for the next generation Internet due to
its flexibility and feasibility compared to OCS and OPS. Moreover, serving as a backbone that interconnects a number of access
networks, OBS ring topologies have been a good choice for solving the current metro gap problem between core network and access
network owning to its simplicity and scalability. In this paper, we provide an insight into the OBS ring network that consists
of nodes using TT–TR (Tunable Transmitter–Tunable Receiver). The node architectures with TT–TR may make efficient use of network
resources even though traffic pattern, such as IP traffic with self-similarity dynamically change, and can support good expandability.
However, all nodes share the limited network resources. This may result in contention such as wavelength contention and transceiver
contention leading to burst loss. In order to use the shared network resources fairly and efficiently as well as reducing
the resource contention, we focus on the design of medium access control (MAC) protocols based on multiple tokens. Each token
is allocated to one wavelength to denote the accessibility of that wavelength, i.e., once the token is captured, the corresponding
wavelength can be used to transmit a burst. As tokens hold the key for using wavelengths to transmit bursts, token management
including the token release time is crucial in the proposed MAC protocols. Thus, two kinds of multiple-token based MAC protocols
with different token release times are proposed: token release after transmitting burst (TRTB) and token release after transmitting
control header (TRTC). Each of them is classified into two schemes called TRTB/TRR and TRTB/RCA and correspondingly TRTC/TRR
and TRTC/ RCA. RCA stands for receive collision avoidance. The target is to increase the performance while reducing the processing
overhead at each node. The performance of the TRTB and TRTC protocols are evaluated and compared in terms of queuing delay,
burst loss rate, and channel utilization by OPNET simulation. The effects of various design parameters are also investigated
through simulation in order to evaluate their scalability. In all the proposed schemes, tokens are just used to denote the
accessibility of each wavelength. Finally, as an alternative, we also propose a new scheme based on the TRTC protocol called
TRTC/CAT (collision avoidance by tokens) to avoid contention by using tokens.
相似文献
Young-Chon KimEmail: |
8.
Contention-Based Limited Deflection Routing Protocol in Optical Burst-Switched Networks 总被引:3,自引:0,他引:3
《Selected Areas in Communications, IEEE Journal on》2005,23(8):1596-1611
Optical burst switching (OBS) is a very promising switching technology for realization of an economical optical Internet. In OBS networks, when contention occurs at an intermediate switch, two or more bursts that are in contention can be lost because a forwarding path reservation is not made for a burst until a control message for the burst arrives. That is the reason why one of the critical design issues in OBS is finding ways to minimize burst dropping resulting from resource contention. In this paper, we propose and analyze a novel deflection routing protocol, which mitigates and resolves contention with significantly better performance as compared with techniques currently known in the literature. While several variants of the basic deflection routing scheme have been proposed before, they all lacked the ability to determine the alternate route based on clear performance objectives. In this paper, we present an on-demand deflection routing scheme, which sequentially performs the following: 1) based on certain performance criteria, dynamically determines if the burst should be deflection routed or retransmitted from source and 2) if the decision is to deflection route, then the same is done using a path that is based on minimization of a performance measure that combines distance and blocking due to contention. The proposed contention-based limited deflection routing scheme prevents injudicious deflection routing. Our simulation results show that the scheme proposed here has much superior performance both in terms of burst loss probability and increased network throughput. Through analytical and simulation modeling, a number of useful insights into the OBS network protocols and performance are provided. 相似文献
9.
A major concern in optical burst-switched (OBS) networks is contention, which occurs when more than one bursts contend for the same data channel at the same time. Due to the bufferless nature of OBS networks, these contentions randomly occur at any degree of congestion in the network. When contention occurs at any core node, the core node drops bursts according to its dropping policy. Burst loss in OBS networks significantly degrades the throughput of TCP sources in the local access networks because current TCP congestion control mechanisms perform a slow start phase mainly due to contention rather than heavy congestion. However, there has not been much study about the impact of burst loss on the performance of TCP over OBS networks. To improve TCP throughput over OBS networks, we first introduce a dropping policy with burst retransmission that retransmits the bursts dropped due to contention, at the ingress node. Then, we extend the dropping policy with burst retransmission to drop a burst that has experienced fewer retransmissions in the event of contention at a core node in order to reduce the number of events that a TCP source enters the slow start phase due to contention. In addition, we propose to limit the number of retransmissions of each burst to prevent severe congestion. For the performance evaluation of the proposed schemes, we provide an analytic throughput model of TCP over OBS networks. Through simulations as well as analytic modeling, it is shown that the proposed dropping policy with burst retransmission can improve TCP throughput over OBS networks compared with an existing dropping policy without burst retransmission. 相似文献
10.
突发包冲突在无光缓存能力的光突发交换(OBS)网络中是一个尚未解决的问题.在对JET协议进行改进的基础上,文章首次提出了一种新型的突发包冲突解决方案,分析了其可行性及相对传统算法的优势. 相似文献
11.
12.
《Lightwave Technology, Journal of》2009,27(24):5563-5570
13.
光突发交换网络中支持QoS的一种竞争处理机制 总被引:3,自引:0,他引:3
分段丢弃是最近提出的一种资源竞争解决方法.该文对尾部丢弃竞争处理方法中存在的弊端进行了分析.提出了改进的头部丢弃处理方法,该方法是当竞争重叠部分长度小于整个后到的竞争突发数据的长度时就丢弃后到突发数据的头部,否则就丢弃整个后到突发数据.为了更好地支持区分服务和尽可能地减少错序,该文还提出了基于优先级的混合封装机制.仿真结果证明基于优先级的混合封装机制和改进的头部丢弃方法联合使用时,对降低分组丢失率及支持区分服务等性能效果很明显. 相似文献
14.
15.
《Communications Magazine, IEEE》2005,43(11):S48-S55
Optical burst switching has been receiving increased attention as a promising technology for building the next-generation optical Internet. This article presents the design and discusses the implementation of an overlay mode optical burst-switched network testbed. A flexible "transceiver + forwarding" edge node architecture is proposed to perform both electronic burst assembly/disassembly and optical burst forwarding. It is designed to provide class of service and wavelength selection for locally generated bursts, and transparency to cut-through bursts. The functional modules of the control plane and related key design issues are presented. In particular, we discuss a scheduling mechanism that efficiently combines two different contention resolutions in space and wavelength domains. Experimental results show the effectiveness of this scheme in reducing burst blocking probability. Furthermore, the performance of the network testbed and corresponding methods of improving it are discussed. 相似文献
16.
17.
光突发交换网络中的闭环竞争解析 总被引:2,自引:0,他引:2
为改善光突发交换网络(OBS)的性能,深入探讨了光突发交换网络中的闭环竞争解析,提出了OBS网络中的主动资源预留方案OBS—RED和显式竞争通知方案OBS—ECN。OBS—RED采用随机早期丢弃策略,即根据数据信道拥塞情况,随机早期地丢弃控制分组。OBS—ECN的实现需要OBS—RED的支持。在OBS—ECN中,不是随机丢弃控制分组,而是将这一信息显式地通知边缘节点,边缘节点再作相应的处理。OBS—RED与OBS—ECN的应用,有利于提高网络吞吐量和链路带宽资源利用率,大大减少数据突发的阻塞概率。 相似文献
18.
This paper proposes a contention resolution scheme considering multicast traffic in optical burst switching (OBS) networks.
In OBS networks, for unicast bursts, contention can be avoided by deflection routing. However, deflection routing cannot be
applied to multicast bursts because multicast bursts are transmitted along light-trees which are fixed, tree-shaped routes.
Therefore, the loss probability of multicast bursts is generally high. To resolve this problem, the proposed scheme introduces
an ingenious offset time assignment strategy which completely avoids contention of multicast bursts due to transmissions of
unicast bursts by strategically assigning additional offset times. Furthermore, in the proposed scheme, unicast bursts avoid
contention with deflection routing. Through simulation experiments, we show that the proposed scheme improves the loss probabilities
of both of unicast bursts and multicast bursts. 相似文献
19.
Optical burst switching (OBS) is regarded as one of the most promising switching technologies for next generation optical
networks. However, the data burst contention problem is still unresolved thoroughly even though slotted OBS (SOBS) is studied
as a new paradigm reducing the blocking rate. In this article, we propose a tree-based slot allocation (TSA) algorithm for
loss-free SOBS networks, where the TSA algorithm originally avoids contention of the time-slots by reserving the time-slots
with different time-slot positions for the source nodes, respectively. In order to manage the time-slots efficiently, we also
propose an OBS superframe, which is a cyclic period and consists of multiple time-slots transmitted by the source nodes toward
the same incoming port of a destination node. In addition, we attempt to optimize multiplexing of the OBS superframes to reduce
wavelength consumption. On the other hand, when incoming traffic is beyond expectation, a source node may need more time-slots
to prevent packet loss because of buffer overflow. For reallocation of the time-slots, we propose a flow control scheme managing
some number of shared time-slots, where a control node adaptively allocates (or redeems) the time-slots to (or from) source
nodes by utilizing the shared time-slots based on fluctuating traffic condition. Simulation results show that the blocking
rate of the proposed TSA–OBS scheme is zero with acceptable queueing delay at moderate traffic offered loads. In addition,
multiplexing optimization simulated in the 14-node NSFNET achieves a 63% reduction of wavelength consumption. Moreover, the
proposed flow control scheme assisting the TSA algorithm maintains a target upper-bound of queueing delay at the source node,
so that packet loss caused by buffer overflow is prevented. 相似文献
20.
Junling Yuan Xuhong Li Jing Zhang Qikun Zhang Yunyang Fu 《Photonic Network Communications》2018,35(2):177-186
Optical burst switching (OBS) is a promising technology for next-generation optical networks. Slotted OBS is an improved version of OBS to reduce burst loss rate, in which wavelength channels are divided into time slots. Slotted OBS has an implicit and under-used property that resources for two bursts with the same source and the same destination are interchangeable. The property further means that resource for a long-distance burst can be partially used by a short-distance burst. In this paper, we utilize the property to design a resource reservation scheme for slotted OBS networks. The scheme reserves a batch of slots every time; the specific number of slots is calculated according to number of arrived bursts and partial success rate (a newly introduced conception in this paper) at each node. Simulation results show that the proposed scheme can get lower burst loss rate, comparing with the well-performing two-way signaling scheme. 相似文献