Data transfer method combining erasure coding and cumulative decoding-status feedback: demonstration on an optical packet-switching network testbed

At a switching node in an optical packet switching (OPS) network, packet contention occurs whenever two or more packets try to reach the same output port of the node at the same wavelength, consequently it degrades network performance. Previous works on optical packet switching flourishingly adopted optical buffering with optical fibre delay line (FDL), wavelength conversion, or deflection routing to resolve packet contention. In this paper, we focus on the optical fibre delay line approach, especially the selection of proper length of FDL under asynchronous variable length packet traffic. As the length of fibre coils equipped in a FDL optical buffering system is impossible to be reconfigured frequently, a proper length of FDL should be determined during manufacture. The motivation is to observe the impact factors on FDL optical system performance in a WDM network scenario, and provide the empirical data as supports to select the proper length of FDL in an OPS node system.

Optical buffering is one of the main obstacles in optical packet switching (OPS) networks. We proposed the network global control strategy to resolve this problem. By introducing the cycled traffic at the edge node and the slot assignment algorithm at the core node, a slotted OPS networks with no contention can be realized. In this network, a good throughput, end to end delay and delay jitter performance can be gotten at high load simultaneously, so it may be a promising candidate for the future optical networks.

Buffering management is a crucial function in current optical packet switching (OPS) networks. To avoid packet blocking due to competition for the same switched path, optical buffering is required to queue packets after a router makes the forwarding decision. In this paper, the author proposed a buffering scheme based on optical code-division multiple access (OCDMA), where each packet is encoded with an optical signature code. An optical coding technique combining spectral-amplitude coding (SAC) and two-code keying (TCK) is introduced to advance the buffering performance regarding packet loss probability. In TCK, the payload bits “1” and “0” of a stored packet are respectively converted to a SAC signal and its complementarity. As the Hamming distance between the coding signals of bits “1” and “0” is extended, the existing drawback that the OCDMA-based buffer capacity is limited by the decoder noise increased with the number of queued SAC packets is resolved. Moreover, an encoder consisting of a fiber Bragg grating (FBG) array is applied for simplifying the system design. A SAC signal and its complementary counterpart can be generated simultaneously without the need of an extra encoder.

One of the difficulties of optical packet switched networks is buffering optical packets in the network. Burstiness of Internet traffic causes high packet drop rates and low utilization in very small buffered OPS networks. In this paper, we propose a new node-based pacing algorithm and show that it can increase the utilization of very small optical RAM buffered core optical packet-switched (OPS) networks.

An optical router with multistage distributed management features for the asynchronous optical packet switching (OPS) network is presented, which can improve switching capacity and all-optical scalability. A compact recycling-fiber-delay-line (Rec-FDL) based collision resolution mechanism is proposed to resolve the contentions for asynchronous and variable length optical packets. The analysis models of stabilities, packet loss rates (PLR) and average packet waiting latencies (PWL) for the router are developed based on the timer based optical packet assembly algorithm. The simulation shows that PLR and PWL for a 400-byte optical packet transmitted in the 32 wavelengths dense wavelength division multiplexing (DWDM) system equal to 3.48 × 10?4 and 0.072 ns, respectively. The non-blocking switching can be realized for the packets with lengths less than the buffer granularity of the Rec-FDL, and the optimized performance for the proposed router can be obtained through properly selecting of the system parameters.

Optical network is a high speed network thus reduce the huge bandwidth demands and increase the internet users. Optical burst switched network is an optical networking technique that allows dynamic sub wavelength. OBS is viewed as compromise the optical packet switching and optical circuit switching networks. OBS networks suffer from various security vulnerabilities. This paper propose a security threat named as Burst Circulating attack for OBS networks and provide defective mechanism for this attack. The ns2 simulator with modified nOBS patch is used simulate and verify the security parameter.

The huge traffic growth which is currently experienced (traffic nearly doubles every year) and foreseen to continue for several years calls for high capacity networks capable of efficiently handling various types of traffic (voice, video, data). WDM (Wavelength Division Multiplexing) optical networks exploiting also fast optical packet switching are expected to provide the required capacity and flexibility for the next generation of high-speed networks. In this context, the European ACTS KEOPS project (KEys to Optical Packet Switching) has concentrated on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. Optical packets of fixed duration have been considered where the payload bit rate, which is user-dependent, can vary from a few hundred Mb/s to 10 Gb/s whereas the header is at a fixed low bit rate (622 Mb/s) to facilitate processing at the network/node interfaces. The challenge addressed by the KEOPS project was therefore to combine the advantages of the relatively coarse-grained WDM techniques with emerging all-optical switching capabilities to yield a high-throughput optical platform directly underpinning next generation data networks (ATM, IP). The project which involved nine partners (Alcatel Alsthom Recherche (F), France Telecom-CNET (F), CSELT (I), Technical University of Denmark (DK), Alcatel CIT (F), Alcatel SEL (D), University of Bologna (I), ETH-Zurich (CH) and University of Strathclyde (UK)) has addressed both network and system studies as well as demonstration experiments based on advanced optoelectronic components developed in the project in order to validate the proposed concept.

Superstructured fiber Bragg grating (SSFBG) can be applied as the optical code (OC) encoder/decoder for optical code division access (OCDMA) and optical packet switching (OPS) networks. OC-based traffic (either OCDM traffic or OC-based packet labels) could be transmitted over the WDM networks to provide higher spectral efficiency and better scalability. The performance of this scheme is investigated for the first time in this paper, particularly the impact of the crosstalk in WDM networks with different channel spacing. These results can be used for assigning the optimal channel-spacing to get the highest spectral efficiency.

In this PhD dissertation multi-rate models are examined for the performance analysis of telecommunication networks through mathematical analysis and simulation. Particular emphasis is given to optical networks. The main goal is the development of analytical models for the calculation of network performance metrics, such as blocking probabilities, transmission delay and utilization of the common channel. The proposed analytical models are distinguished according to the network technologies. Three different technologies are considered: A) Wavelength routed optical networks. B) Optical access networks. C) Wireless Internet access networks. Multi-rate loss models are proposed for the performance evaluation of wavelength routed optical networks. Firstly, the case of a single link is considered and then a mesh all-optical network is examined. In addition, analytical models are proposed for Optical Packet Switching (OPS) networks, for the case of an all-optical OPS switch and of an OPS mesh network. Multi-rate analytical models are proposed for the evaluation of the performance of Passive Optical Networks (PONs) implementing different multiple access methods. For the case of Time Division Multiple Access (TDMA) the Ethernet PON is studied, which supports multiple service-classes. Regarding the Wavelength Division Multiplexing (WDM) PONs a hybrid WDM-TDMA PON is considered and the call-level performance is evaluated. Calls are distinguished by their arrival process, which can be random or quasi random, by their bandwidth requirements, which can be fixed of elastic and by their behavior during their service, which can be calls of fixed transmission rate or calls that alternate between ON and OFF periods. Finally multi-rate loss models are proposed for the case of Optical Code Division Multiple Access (OCDMA) PONs that take into account the user activity and the presence of additive noise in the transmission channel. For the performance analysis of wireless Internet access networks analytical models are proposed, which implement the IEEE 802.11 protocol or the IEEE 802.11e protocol. The proposed analysis calculated the saturation throughput and the end-to-end packet delay as a function of the Medium Access Control (MAC) delay and the queueing delay. In all cases the accuracy of the proposed models is validated through simulation.

The great contributions in optical networks added the optical burst switching (OBS) networks that are outperforming in advance methods referred to as optical circuit switching and optical packet switching networks in the direction of switching and transmitting data through optical fibres. The critical and obligatory factors in OBS are assembling the bursts, routing, resource (such as transmission channels) scheduling, and burst segmenting for optimal transmission. Hence, the current research is focusing on these either of divergent factors of OBS and putting efforts to contribute optimal approaches to assemble, route, schedule or segment. In this paper, the segmentation scheme is investigated through simulation and it is shown that segmentation with void filling can achieve a significantly reduced burst loss rate.KeywordsOptical burst switchingBurst drop ratio

Analytic and approximate traffic model is proposed for asynchronous optical packet switching (AOPS) networks to serve the network performance analysis. The study shows that AOPS network traffic could be modeled as Poisson arrival with Gaussian-distributed packet size, when the timeout-based optical packet assembly algorithm is adopted and the incoming IP traffic at AOPS edge routers is short-range dependent. These findings are helpful to accurately dimension the traffic model for AOPS networks.

Traditional Forward Error Correction (FEC) mechanisms can be divided into Packet level FEC (PFEC) mechanisms and Byte level FEC (BFEC) mechanisms. The PFEC mechanism of recovering from errors in a source packet requires an entire FEC redundant packet even though the error involves a few bit errors. The recovery capability of the BFEC mechanism is only half of the FEC redundancy. Accordingly, an adaptive Sub-Packet FEC (SPFEC) mechanism is proposed in this paper to improve the quality of video streaming data over wireless networks, simultaneously enhancing the recovery performance and reducing the end-to-end delay jitter. The SPFEC mechanism divides a packet into n sub-packets by means of the concept of a virtual packet. The SPFEC mechanism uses a checksum in each sub-packet to identify the position of the error sub-packet. Simulation experiments show the adaptive SPFEC mechanism achieves high recovery performance and low end-to-end delay jitter. The SPFEC mechanism outperforms traditional FEC mechanism in terms of packet loss rate and video Peak Signal-to-Noise Ratio (PSNR). SPFEC offers an alternative for improved efficiency video streaming that will be of interest to the designers of the next generation environments.

As new bandwidth-hungry IP services are demanding more and more capacity, transport networks are evolving to provide a reconfigurable optical layer in order to allow fast dynamic allocation of WDM channels. To achieve this goal, optical packet-switched systems seem to be strong candidates as they allow a high degree of statistical resource sharing, which leads to an efficient bandwidth utilization. In this work, we propose an architecture for optical packet-switched transport networks, together with an innovative switching node structure based on the concept of per-packet wavelengthrouting. Some simulations results of node operation are also presented. In these simulations, the node performance was tested under three different traffic patterns.KeywordsTransport NetworkWavelength ConversionOptical Burst SwitchingPacket LengthOptical PacketThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Packet contention is a major issue in optical packet switching network. To resolve contention, optical buffering approach is used using Fiber Delay Lines (FDLs). Yet there is a heavy packet loss rate due to unavailability of output-port and free FDLs. This paper proposes a selective minimum delay value algorithm (SMDV) to resolve contention for shared FDL buffering architecture in order to ensure the availability of output-port for the contended packet after coming out from FDL. Simulation result shows that proposed scheme can achieve a packet loss rate of ~ even at heavy traffic load 0.9 for 32×32 switch using 32 variable length FDL.

This paper deals with massive number of optical code (OC) label generation and recognition for scalable optical packet switching (OPS) networks. In order to expand the system scalability of code label processing, we develop a record port count 128 x 128 optical encoder/decoder (E/D) and propose a novel three-dimensional (3-D) optical label combining code label with wavelength and polarization. In the experiment, we conduct a proof-of-concept demonstration of 4-code x 2-wavelength x 2-polarization and validate that the 3-D labeling scheme can consequently increase the available number of code label up to more than 1,000 labels. Real-time labeling performance using a field programmable gate array (FPGA)-based processor and crosstalk influence at an optical switch are also experimentally evaluated.