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For the practical deployment of optical packet switching (OPS) system, realizing all-optical buffering is a critical issue. In this paper, we present a hybrid labelling scheme based on optical code-division multiplexing (OCDM) over generalized multi-protocol label switching (GMPLS) network. The virtual optical memory is implemented by assigning queuing packets with different coded-WDM labels. The proposed hybrid labels combine the advantages of wavelength-division multiplexing (WDM) with spectral-amplitude-coding (SAC) OCDM. Due to the cyclic-shift property of arrayed-waveguide grating (AWG) and maximal-length sequence (M-sequence) codes, blocks of label generating and processing in node organization can be built in low complexity. Furthermore, utilizing hybrid coding technique in the buffering node increases the efficiency of label generating and processing. Derivation of the probability of packet missing is done to quantify the buffering performance of virtual optical memory. Simulation results show that the hybrid-coded labels, as compared to the conventional OCDM labels, are able to buffer the data packets with a relatively low probability of packet missing under similar label length. [ABSTRACT FROM AUTHOR]

Abstract: Optical Label Switching (OLS) has been considered to be a promising approach to realize optical packet switching (OPS) networks. In an OLS router, the header processing module retrieves the routing information carried in the optical header and then replaces the old header with a new one through optical label swapping. The cost-effectiveness and the speed of performing label swapping are two major concerns. Due to lack of optical random access memory, optical label swapping has become a big challenging issue in implementing OLS switches. To overcome these difficulties, in this paper, we propose two Linear Random Code (LRC)-based label encoding schemes to achieve label swapping free OPS networks. Using the proposed schemes, a small sized label is needed. Only simple modulo-2 multiplication and modulo-2 addition operations are required to decode an optical label and there is no optical label swapping during packets traverse along the entire routing path. In our system, each source–destination pair is assigned multiple paths so the network is with traffic engineering and fault tolerance capabilities. We have carried out extensive simulations to evaluate the performance of the proposed scheme. Compared with the well-known KIS encoding scheme, the proposed LRC-based scheme can reduce the label size significantly. An 8-byte LRC label is long enough to support all node pair with five paths in a 300-node network. [Copyright &y& Elsevier]

Abstract: Optical packet switch with multicast capability can inspire a broad range of multipoint to multipoint applications in future optical networks. An optical multicast packet switching architecture, equipped with feedback shared small number of limited-range multi-wavelength converters (LMWCs) and output shared some full-range wavelength converters (FRWCs), is proposed for a wavelength-division multiplexed optical multicast network to improve multicast performance in the paper. The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to only use LMWCs. In the architecture, the two converters are shared by all the multicast packets importing to the optical multicast switch node. A maximum bipartite matching with minimum edges weights strategy was designed to employ fewer wavelength converters and avoid useless degradation of optical signal quality for the architecture to improve the node performance. The simulation results show that the proposed architecture and its wavelength converter scheduling algorithm can reduce the multicast packet loss probability with relatively lesser wavelength conversion cost. [Copyright &y& Elsevier]

Abstract: We proposed and investigated superimposing intensity-modulated labels onto high-speed carrier-suppressed return-to-zero frequency shift keying-modulated payloads in optical label-switching packet networks. The transmission performances of 2.5Gb/s ASK label on 40Gb/s CSRZFSK payload is studied for the first time. [Copyright &y& Elsevier]

Abstract: Optical burst switching is a promising all-optical switching technology for the next generation optical networks and signaling is one of the key components of it. According to propagation direction of control packets, the existing signaling schemes for optical burst switched networks can be roughly divided into three categories: one-way, two-way, and hybrid signaling. Since one-way signaling launches bursts without the acknowledgment of successful reservation of resources, it has small end-to-end delay but high data loss rate; two-way signaling uses a control packet to gather the state of links and needs the successful acknowledgment before sending out a burst, so it has large end-to-end delay but low data loss rate. A hybrid signaling gets a tradeoff of performance between one-way and two-way signaling. In this paper, we propose another hybrid signaling named inverse two-way signaling. By introducing the process of link state collection into one-way signaling, the inverse two-way signaling can decrease the data loss rate without increasing the end-to-end delay compared to one-way signaling. In other words, the inverse two-way signaling is an improved version of one-way signaling. [Copyright &y& Elsevier]

Abstract: Packet-switching WDM ring networks with a hotspot transporting unicast, multicast, and broadcast traffic are important components of high-speed metropolitan area networks. For an arbitrary multicast fanout traffic model with uniform, hotspot destination, and hotspot source packet traffic, we analyze the maximum achievable long-run average packet throughput, which we refer to as multicast capacity, of bi-directional shortest path routed WDM rings. We identify three segments that can experience the maximum utilization, and thus, limit the multicast capacity. We characterize the segment utilization probabilities through bounds and approximations, which we verify through simulations. We discover that shortest path routing can lead to utilization probabilities above one half for moderate to large portions of hotspot source multi- and broadcast traffic, and consequently multicast capacities of less than two simultaneous packet transmissions. We outline a one-copy routing strategy that guarantees a multicast capacity of at least two simultaneous packet transmissions for arbitrary hotspot source traffic. [Copyright &y& Elsevier]

Abstract: In the Optical Burst Switching (OBS) Network, the burst assembly technique is one of the challenging issues in the implementation of the system. It has the influence on the burst characteristic, which gives an impact on the network performance. Burst assembly is the process of assembling incoming data from the higher layer into bursts at the ingress edge node of the OBS network. The burst assembly mechanism must then place these packets into bursts based on some assembly policy. In this paper, the OBS system performance has been observed in simulated 12-node network based on Just-Enough-Time (JET) reservation protocol with various burst assembly techniques under the standard drop policy (DP) and the segmentation policy for contention resolution. The simulation results show that the performance of the proposed Adaptive-Threshold with Fixed Maximum Time Limitation (ATH-FMTL) burst assembly scheme is better than conventional burst assembly schemes in terms of loss probability and average assembly delay. Also, the proposed scheme avoids a sudden increase in the burst size and makes the burst sent out smoother as compared to conventional schemes. [Copyright &y& Elsevier]

Abstract: TCP-over-OBS is a promising transport paradigm to support next-generation Internet. It is well known that load-balanced routing generally improves loss performance over OBS. We identify that implementing TCP over load-balanced OBS could lead to persistent out-of-order delivery of TCP segments, resulting in unnecessary timeouts and fast retransmissions. In this paper we evaluate the performance of Reordering-Robust TCP (RR-TCP) over OBS networks. We develop an analytical end-to-end transfer delay model for TCP SACK and RR-TCP over load-balanced OBS networks. We observe that standard TCP experiences significant throughput degradation due to persistent packet reordering. Through simulations and modeling we show that RR-TCP achieves significant improvement compared to TCP SACK. In our simulations we add High-Speed TCP functionality to RR-TCP (HS-RR-TCP). The simulations show up to a 300% performance improvement for HS-RR-TCP compared to HS-TCP-SACK under ideal conditions and a 20% improvement on NSFnet with background traffic. [ABSTRACT FROM AUTHOR]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: A novel scheme of time-stacked optical code label based on optical code division multiple (OCDM) technique for optical packet switching network is proposed, in which two-dimensional wavelength–time OCDM code is used as the optical label. Packet loss rate and system characteristic based on the proposed scheme are studied. Results show that less packet loss rate of proposed scheme can be achieved as compared with that of one-dimension time-stacked optical code label system. [Copyright &y& Elsevier]

Abstract: In this paper, an optically controlled loop buffer is proposed and experimentally demonstrated. It utilizes a semiconductor optical amplifier (SOA) based loop mirror as a fast switch to realize the writing and reading of packets within this buffer and a circulator based optical reflector to achieve internal re-circulations. By adding fibers with different lengths between the loop mirror and the circulator, variable delay time per circulations can be obtained. We also demonstrate the performance of the 2.5 and 10Gb/s data packets in this buffer structure, as well as the influence of the two different control signal formats on the packet signal degradation during buffering. This loop buffer has the merits of low cost and improved performance compared to other similar loop buffer structures. According to the obtained results, the achieved number of circulations is greatly increased. [Copyright &y& Elsevier]

Abstract: Metropolitan Area Networks (MANs) are considered one of the best arenas for an early introduction of optical packet switching technologies. However, there is still no clear definition of how these technologies should be exploited in the design of innovative MANs. In this paper we consider different architectures that have been studied in the framework of the European Network of Excellence e-Photon/ONe and analyze their advantages and limitations. The main contribution of this work is the proposal of an analytical framework to compare these architectures in terms of resource demand when dimensioning them for a given traffic matrix and, from this analysis, discuss issues and trade-offs arising in the design of optical packet MANs. [Copyright &y& Elsevier]

Abstract: A novel scheme of optical-code label (OC-label) switching based on a special optical packet generation where the payload and the OC-label are located in different spectrum section is proposed. The payload and the OC-label are separated using a fiber Bragg grating (FBG) without any strict timing. The results of the simulation verified the feasibility of the scheme. [Copyright &y& Elsevier]

In this paper, we investigate the performance of optical packet switches. Optical packet switches are operated entirely in the optical domain (except for the header extraction). The optical buffering is realised by using fiber delay lines (FDL's). We analyse, using generating functions, an optical buffering structure, consisting of FDL's with increasing lengths. We use this analysis to investigate the packet loss rate (PLR) in two types of switches with output buffering. [ABSTRACT FROM AUTHOR]