S. De Maesschalck

Intelligent optical networking for multilayer survivability

In recent years, telecommunication networks have faced explosive (IP) traffic growth. As traffic keeps growing, network reliability gains more and more importance. This article investigates to which extent switched connections and fast connection provisioning, typical for intelligent optical networks (IONs), can be used to provide resilience in an IP-over-optical multilayer network scenario. This solution, based on transport network flexibility, is compared with more traditional static multilayer resilience schemes in terms of cost (capacity) requirements and operational (dis)advantages.

Benefits of GMPLS for multilayer recovery

IP-based backbone networks are gradually moving towards a network model consisting of high-speed routers that are flexibly interconnected by lightpaths set up by an optical transport network consisting of WDM links and optical cross-connects. Recovery mechanisms at both network layers are crucial to reach the high availability requirements of critical services. In such a model, the GMPLS protocol suite can provide a distributed control plane that can be used to deliver rapid and dynamic circuit provisioning of end-to-end optical lightpaths. This article explains that it can be very beneficial to exploit this functionality to enhance the cost effectiveness of multilayer recovery significantly. Several practical case studies illustrate this concept and highlight the opportunities and challenges to be faced.

Multi-layer traffic grooming in networks with an IP/MPLS layer on top of a meshed optical layer

Traffic grooming in networks employing WDM is gaining attention due to the difference between the bandwidth requirements of the traffic demands coming from the client layer and the capacity of a wavelength in an optical transport network (OTN). In this paper an algorithm for efficient traffic grooming in a multi-layer IP/MPLS-over-meshed OTN scenario is presented. It allows designing the IP/MPLS logical topology best suited to deal with the offered traffic pattern, taking into account the unidirectional and maybe asymmetric character of IP traffic. This multi-layer traffic grooming algorithm is based on the idea of charging the IP/MPLS layer for the capacity it consumes in the optical layer. In order to assess its performance, a comparison with other grooming approaches is made. The results show that our method allows for serious savings in the overall network design cost. It also allows for a gradual capacity installation in the network, thus spreading the installation cost.

Efficient Protection in MPλS Networks Using Backup Trees: Part Two—Simulations

In Part One of this study [1], we presented three approaches for organizing backup tree (BT) protection, where a BT was used to protect a group of working paths (WPs) against single failures. Shared BT protection uses less capacity compared to d edicated (path) protection (DP), while having the same fast recovery. Using shared BT protection is particularly suitable for multi-protocol lambda switching (MPλS) networks and can save about 15% capacity resources compared to DP. In this paper, we present a simulation study in which we apply the approaches presented in Part One for several network topologies with different demand scenarios. The effects of network and demand characteristics on the capacity gain obtained with these approaches are analyzed. In addition, the comparison between BTs and 1 : N protection is made.

Traffic Studies for Fast Optical Switching in an Intelligent Optical Network

The optical layer of the transport network is expected in the (near) future to make the transition from a statically configured layer to a fully flexible, automatic and intelligent layer. Such an intelligent optical network (ION) allows to set up (or tear down) bandwidth between two nodes on demand, following a simple request of the client network layer: the so-called switched connections. For successful deployment of these switched connections it is of utmost importance to have a well-educated idea about the granularities of the traffic flows in the optical transport network. Deploying switched connections with a capacity of 10 Gbps to transport a traffic demand with a granularity of a few hundred Mbps does not exactly make efficient use of the network resources. In this paper, the granularity of the traffic demand between US metro areas is investigated for two future points in time, namely 2006 and 2010. For this study we focus on the traffic flows between two metro area entities: the points of presence (PoPs) or the main aggregation points of the customer traffic in a metro area, and the collector central offices (COs) or the nodes a bit further in the metro area, closer to the end-customers. We have found that a significant portion of the total traffic volume at these moments in time will qualify for transport using switched connections with a capacity of 10 Gbps. According to our study, in 2006 around one third of the traffic will qualify for transportation in such 10 Gbps connections between PoPs in different metro areas, while by 2010 this amount will have increased to more than 99%. The traffic granularity between the collector COs, however, will in 2006 still be too small to justify the use of direct 10 Gbps connections, but in 2010 almost three quarter of the traffic could make use of 10 Gbps direct connections from collector CO to collector CO. These results enable us to sketch the expected network evolution scenario and determine the type and size of equipment needed in the different steps of the network evolution. The optical edge aggregation switches will have to be moved deeper into the metro area with time: in 2006 they will be needed at the PoPs, while by 2010 they could be placed at the collector COs.

How the asymmetric nature of IP traffic influences the cost of the underlying optical layer

In this article the influence of the asymmetric nature of (IP) traffic on the cost of the underlying optical transport network is investigated over a time frame of six years using a realistic traffic forecast for a European fiber-optic network. The currently deployed transport networks contain bidirectional optical line systems and are thus inherently symmetric, although the traffic that has to be conveyed over those networks is asymmetric. This article shows that a cost reduction of up to 38% can be obtained if the bidirectional line systems are replaced by unidirectional ones.In this article the influence of the asymmetric nature of (IP) traffic on the cost of the underlying optical transport network is investigated over a time frame of six years using a realistic traffic forecast for a European fiber-optic network. The currently deployed transport networks contain bidirectional optical line systems and are thus inherently symmetric, although the traffic that has to be conveyed over those networks is asymmetric. This article shows that a cost reduction of up to 38% can be obtained if the bidirectional line systems are replaced by unidirectional ones.

Design and experiments of an automatic switched optical network (ASON)

This paper describes the activities and the preliminary results of the IST Project LION (Layers Interworking in Optical Networks), whose main objective is to design and test a robust and managed transport network based on an automatic switched optical network (ASON).

Asymmetric IP traffic and its consequences for the optical layer

This paper studies the influence of the asymmetric nature of IP traffic on the cost of the underlying optical transport network, which contains bidirectional optical line-systems and is thus inherent symmetrical.

Circuit/wavelength switching and routing

This paper gives an overview of the work carried out during the course of the COST-266 action on circuit/wavelength switched network studies. Several subjects are discussed in detail in this paper. A first important topic deals with the different control plane models in single- and multidomain networks. A second important issue is the routing and wavelength assignment problem, both in networks with static and dynamic traffic demands. Also the IP-over-OTN network architecture, envisaged to be the network architecture most suited for future transport networks, is discussed. Finally the study on optical virtual private networks is presented.

Developing control plane models for optical networks

In this paper, a new border gateway protocol (BGP) control plane model, which combines the advantages of the wellknown overlay and peer models is proposed, together with preliminary requirements for the extensions to the BGP to realize this control plane model.