Slotted Optical Packet Research Articles

Packet Loss Rate Differentiation in slotted Optical Packet Switching OCDM/WDM

Packet Loss Rate Differentiation in slotted Optical Packet Switching OCDM/WDM

Packet Loss Rate Differentiation in slotted Optical Packet Switching OCDM/WDM

We propose a multi-class mechanism for Optical Code Division Multiplexing (OCDM), Wavelength Division Multiplexing (WDM) Optical Packet Switch (OPS) architecture capable of supporting Quality of Service (QoS) transmission. OCDM/WDM has been proposed as a competitive hybrid switching technology to support the next generation optical Internet. This paper addresses performance issues in the slotted OPS networks and proposed four differentiation schemes to support Quality of Service. In addition, we present a comparison between the proposed schemes as well as, a simulation scheduler design which can be suitable for the core switch node in OPS networks. Using software simulations the performance of our algorithm in terms of losing probability, the packet delay, and scalability is evaluated.

Contentionless transmission in buffer-less slotted optical packet switched networks

Abstract Contention of optical packets in optical packet switched (OPS) networks is a major problem, and it is even more critical in buffer-less OPS networks. In this paper, an innovative contention avoidance technique is proposed which uses combination of special traffic shaping at ingress switches and special time slot reservation technique through the path of traffic flows in core network. This novel protocol is called contentionless transmission OPS (CLTOPS) suitable for buffer-less slotted OPS networks. Performance evaluations show that the CLTOPS can outperform the original slotted-OPS architecture in terms of packet loss rate (PLR) performance, with or without using wavelength conversion. It is shown that there is a trade-off between the amount of improvement in PLR and additional delay applied to the users’ packets at the ingress switches buffers. However, appropriate parameters can be selected to make the additional delay tolerable for users’ applications.

Capacity-enhanced receivers for low-latency Burst Optical Slot Switching rings

We propose a new receiver architecture for coherent detection in slotted optical packet switching rings with elastic (rate adaptive) optical transponders. Such rings are a candidate solution for future datacenter and metropolitan networks. The new receiver can detect more than a single packet per time slot and consequently has higher flexibility (translating into higher supported capacity, or, equivalently, lower end-to-end latency, or a combination or both), at the cost of a moderate increase in the transponder complexity and energy consumption (less than 10 %). We apply network planning and traffic engineering simulation tools (which we validate on small examples using theoretical models) to quantify the increase in network capacity and latency reduction that can be achieved thanks to the use of the new receivers. Finally, we identify the stability problem of the insertion process in the rings with the coherent receivers and propose a polynomial network planning algorithm, for the case of fast-tunable transmitters. We evaluate the cost of enforcing the stability, in terms of the additional transponders needed, for the mentioned case.

Contention avoidance in bufferless slotted optical packet switched networks with egress switch coordination

Optical packets contention in optical packet switched (OPS) networks can lead to Optical packet loss which will reduce network performance. In this paper, a new contention avoidance technique is proposed which utilizes the combination of traffic shaping at ingress switches and a time slot reservation technique using the coordination of egress switches. This novel protocol is called egress coordination OPS (EGCOPS) suitable for buffer-less slotted-OPS networks. Simulation results show that the EGCOPS outperforms the original slotted-OPS protocol in terms of optical packet loss rate (PLR), with or without using wavelength conversion. However, the packet shaping feature of EGCOPS can increase the delay of users’ packets at the queues of ingress switches. There is a trade-off between the PLR improvement and the additional delay applied to the users’ packets. Still, EGCOPS parameters can be selected in such a way that additional delay can be tolerable by users’ applications.

Performance Analysis of Slotted Optical Switching Scheme using Non-uniform Traffic Pattern

In this paper, we present the performance analysis of bufferless slotted optical packet switching using non uniform traffic pattern. The mathematical analysis has been done to evaluate the packet loss rate and also compared with the existing uniform traffic pattern. In addition to this, we have also studied the performance of the non uniform traffic pattern with the uniform traffic pattern of various packet sizes. Under non-uniform traffic pattern, packet loss rate is very much reduced compared to the uniform traffic pattern and more number of packets has been transmitted for the same period of time.

Packet contention resolution in slotted optical packet switch using ant-colony based algorithm

An ant-based contention resolution scheme for the slotted optical packet switched networks has been proposed, and the optimal number of fibre delay lines (FDLs) used in the switch under various traffic loads is investigated. The proposed algorithm can makes FDLs and output port assignment so as to improve the cell-loss rate under various traffic loads. It is found for traffic loads 0.9, 0.6, 0.3, the optimum value for FDL is 64 128 and 128.

Parallel desynchronized block matching: A feasible scheduling algorithm for the input-buffered wavelength-routed switch

The input-buffered wavelength-routed (IBWR) switch is a promising switching architecture for slotted optical packet switching (OPS) networks. The benefits of the IBWR fabric are a better scalability and lower hardware cost, when compared to output buffered OPS proposals. A previous work characterized the scheduling problem of this architecture as a type of matching problem in bipartite graphs. This characterization establishes an interesting relation between the IBWR scheduling and the scheduling of electronic virtual output queuing switches. In this paper, this relation is further explored, for the design of feasible IBWR scheduling algorithms, in terms of hardware implementation and execution time. As a result, the parallel desynchronized block matching (PDBM) algorithm is proposed. The evaluation results presented reveal that IBWR switch performance using the PDBM algorithm is close to the performance bound given by OPS output buffered architectures. The performance gap is especially small for dense wavelength division multiplexing (DWDM) architectures.

Contention Reduction in Core Optical Packet Switches Through Electronic Traffic Smoothing and Scheduling at the Network Edge

A contention-aware packet-scheduling scheme for slotted optical packet switching (OPS) networks is proposed, which employs edge-traffic shaping to reduce contention, coupled with a modified type of renegotiated service incorporating rate prediction. Queuing and scheduling of traffic is implemented electronically within the edge nodes, shaping user traffic into streams, which have a fixed bit rate only for a short period, which is renegotiated at regular intervals in response to user requirements and network conditions. Via an appropriate protocol, edge nodes gain knowledge of relevant network scheduling and topology information. This is used to schedule user-data packets appropriately, in order to reduce contention. Simulation and analytical results demonstrate that in the core, under typical conditions, packet loss below 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> may be obtained, with a load of 0.8 and with core optical-packet switch buffers having only 20-slot capacity. The tradeoffs between parameters affecting such results are investigated, demonstrating clearly that much more modest optical core buffers than previously thought necessary can provide acceptable performance. The performance and scalability of these proposals are investigated and discussed, demonstrating their feasibility

Traffic models for slotted optical packet switched networks

Optical packet switching (OPS) has emerged as a promising architecture for the future all-optical network scenario. In order to have a successful deployment of OPS networks, several networking issues must be resolved, e.g., how to resolve contentions and how to provide Quality-of-Service (QoS) differentiation. Such networking studies often rely on teletraffic analysis in order to quantify the performance of the OPS network. In this paper, we introduce new and review existing traffic models for slotted buffer-less OPS networks. In particular, we present a novel asymmetric traffic model, suitable for studying the effects of non-uniform traffic. Optical packet switches with and without wavelength conversion are studied. Numerical evaluations and a comparison study of the presented traffic models are reported. The main contributions of this paper are to advance the field of establishing a theoretical framework for slotted OPS networks and to act as a tutorial for teletraffic engineering in such networks.

Contention resolution in slotted WDM optical packet switching networks using cascaded auxiliary switch

A contention resolution scheme for slotted optical packet switching networks is proposed. The optical switch is augmented using auxiliary output ports connected to an auxiliary switch through fibre delay lines. The node architecture is illustrated and the results of the model show that packet blocking probability is improved using the proposed scheme.

Packet loss rate differentiation in slotted optical packet switched networks

This letter presents a packet loss rate (PLR) differentiation scheme suitable for slotted optical packet switched networks. An analytical model of the proposed scheme is presented and expressions for the PLRs are derived for a multiclass scenario. We also show that the use of the proposed scheme does not result in any reductions in the average switch throughput.