Packet-based optical access ring is becoming a promising solution in metropolitan networks. Its performance depends mainly on how optical resource sharing takes place among the different competing access nodes. This network architecture has mostly been explored with regard to synchronous transmission, i.e., slotted wavelength-division multiplexing (WDM) ring. However, in this paper, we focus on the performance of asynchronous transmission-based networks with variable packet sizes. Analytical models are presented in an attempt to provide explicit formulas that express the mean access delay of each node of the bus-based optical access network. We prove that in such a network, fairness problems are likely to arise between upstream and downstream nodes sharing a common data channel. Furthermore, we show that sharing the channel's available bandwidth fairly but arbitrarily between access nodes, as in slotted WDM rings, does not resolve the fairness problem in asynchronous system. In this regard, we exhibit the inherent limitations of the token bucket access rate-based algorithm once applied to asynchronous transmission bus-based networks. To alleviate the aforementioned problem, we device a new strategy called traffic control architecture using remote descriptors. The proposed solution is based on a preventive mechanism to grant access to the shared resource. As illustrated in this paper, the proposed solution alleviates the performance degradation and the resource underutilization, while achieving fairness among bus nodes.

Resolving the fairness issues in bus-based optical access networks

Packet-based optical access ring is becoming a promising solution in metropolitan networks. Its performance depends mainly on how optical resource sharing takes place among the different competing access nodes. This network architecture has mostly been explored with regard to synchronous transmission (i.e., slotted WDM ring). However, in this article we focus on the performance of asynchronous transmission-based networks with variable packet sizes. We investigate the fairness issue that is likely to arise between upstream and downstream nodes sharing a common data channel. Furthermore, we show that sharing the channel's available bandwidth fairly but arbitrarily between access nodes, as in slotted WDM rings, does not resolve the fairness problem in asynchronous systems. In this regard, we exhibit the inherent limitations of the token bucket access rate-based algorithm once applied to asynchronous transmission bus-based networks. To alleviate the aforementioned problem, we devise a new strategy called traffic control architecture using remote descriptors (TCARD). The proposed solution is based on a preventive mechanism to grant access to the shared resource. As illustrated in the article, the proposed solution alleviates performance degradation and resource underutilization while achieving fairness among bus nodes.

Resolving the fairness issue in bus-based optical access networks

A method for operating a packet based data network (21; 31), the data network (21; 31) comprising a multitude of nodes (A, B, C, D) and a shared data bus (22; 32), wherein at least some of the nodes (A, B, C, D) add traffic to the data bus (22; 32), and wherein the upstream nodes (A, B, C, D) reserve data transfer capacity of the data bus (22; 32) for downstream nodes (A, B, C, D) by means of a fairness mechanism, is characterized in that at least some of the nodes (A, B, C, D) drop traffic from the data bus (22; 32), and that said fairness mechanism takes into account the drop traffic at downstream nodes (A, B, C, D). The inventive method allows a better bandwidth utilization and uses available resources more efficiently.

Method for operating a packet based data network

The recent trend in optical networks is switching packets directly in the optical domain. The aim is to benefit from both packet flexibility and optical transparency. In this article, we review current optical architectures that try to reconcile these two requirements. We discuss the challenges encountered in these new architectures and their respective niches. To meet the requirements of next-generation high-speed optical networks, we also propose a new solution based on the distribution of the aggregation process in the network. The feasibility of this scheme and the benefit that it provides over existing solutions are analyzed in this article.

/pdf/sub-wavelength-solutions-for-next-generation-optical-2flmbun15t.pdf

Sub-Wavelength Solutions for Next-Generation Optical Networks

politan area networks. In DBORN, metro clients like enterprise networks are connected to the optical metro-ring by edge nodes which share the wavelength channels on the ring. In order to allow for a high-speed optical interface on the upstream wavelengths while avoiding active optical switching components, a carrier sense multiple access/collision avoidance (CSMA/CA) medium access control (MAC) protocol is realized. A Fairness protocol so-called TCARD was proposed [2] to tackle with the positional priority problem and provide guaranteed QoS. In this paper, the MAC protocol and the closely related transmitter interface are described first. Then, the performance of the MAC protocol is evaluated with respect to important system parameters like slotted/unslotted operation mode, burst size distribution and node position in terms of the mean waiting time as well as the node-to-hub delay. The performance of TCARD is inspected through simulations with respect to different parameter settings. Based on the original TCARD protocol in asynchronous unslotted operation mode, we also introduce slotted TCARD for the slotted operation mode and obtain outstanding performance gains.

http://ieeexplore.ieee.org/iel5/9770/30813/01427029.pdf

Performance of MAC layer and fairness protocol for the dual bus optical ring network (DBORN)

In this paper, we propose and evaluate a new concept of traffic aggregation in mesh networks that aims to eliminate the bandwidth underutilization problem existing in all-optical wavelength routed networks. The proposed solution is based on the distribution of the aggregation process. So, instead of limiting the utilization of lightpaths capacity to the ingress node, each node along the path is allowed to fill on the fly this optical resource according to its availability. Therefore, the lightpath will be shared by several connections traveling from multiple ingress nodes to a single egress node. This technique combines the benefits of optical bypass and the statistical multiplexing gain. In order to gauge the value of the proposed solution, we formulate the problem using integer linear programming and study its performance through different scenarios using a prototype network. Our results show that distributed aggregation technique can improve significantly the network throughput and reduce the network cost.

Distributed aggregation in all-optical wavelength routed networks

We present and evaluate a novel protocol of traffic control that aims at solving the fairness issue typical of shared medium networks such as metropolitan rings. The proposed solution called TCARD (Traffic Control Architecture using Remote Descriptors) is based on a preventive mechanism to grant access to the resource -- i.e. free bandwidth is preserved by a node according to the traffic requirements from the other network nodes. A review of the existing methods used to manage fairness in ring networks is done and points out their inherent problems (performance issues, resource wastage or inadequacy). In contrast, we show how the new protocol addresses the above limitations, notably through a performance evaluation study. The major conclusion is the ability to avoid the degradation in performances and the resource sub-utilization while achieving fairness within the network.

Matching Fairness and Performance by Preventive Traffic Control in Optical Multiple Access Networks

Packet-based optical ring becomes the standard access medium in metropolitan networks. Its performance depends mainly on how optical resource sharing, among different competing access nodes, takes place. This network architecture has mostly been explored in regard to synchronous transmission. However, in the present paper, we focus on the performance of asynchronous transmission-based metropolitan networks with variable packet sizes. An analytical model is presented in an attempt to provide explicit formulas that express the mean access delay of each node of the bus-based optical access network. In addition, we prove that in such a network, fairness problems are likely to arise between upstream and downstream nodes sharing a common data channel. Furthermore, we show that sharing the available bandwidth fairly and arbitrarily between access nodes, as in slotted WDM rings, doesn’t resolve the fairness problem in asynchronous system.

/pdf/fairness-issues-in-bus-based-optical-access-networks-3rkj7bvbrv.pdf

Nizar Bouabdallah

Papers

Resolving the fairness issues in bus-based optical access networks

Resolving the fairness issue in bus-based optical access networks

Distributed aggregation in all-optical wavelength routed networks

Matching Fairness and Performance by Preventive Traffic Control in Optical Multiple Access Networks

Fairness Issues in Bus-Based Optical Access Networks