Juan Pedro Fernández-Palacios

Dynamic routing and spectrum (re)allocation in future flexgrid optical networks

Future flexible-grid elastic optical networks are very promising due to their higher spectrum efficiency and flexibility comparing to the rigid spectrum grid optical networks realized with the traditional wavelength division multiplexing (WDM) technology. The maturity of key system components enabling flexgrid optical networks, such as advanced modulation techniques and multi-granular switching, is already high enough and thus their deployment is expected in the near future. The main feature of such networks is the removal of fix grid-space assignment (in general 50GHz) to the optical connections independently of the required bandwidth. In fact, the available optical spectrum in flexgrid network is divided into frequency slots of a fixed spectrum width and an optical connection can be allocated into the number of slots that better matches the actual bandwidth of the connection demand. Nonetheless, such allocation must satisfy two constraints, i.e. the slots must be (i) contiguous in the spectrum domain and (ii) continuous along the links on the routing path. These constraints result in a need for dedicated Routing and Spectrum Allocation (RSA) algorithms able to operate under dynamic traffic conditions. From the network design perspective, an important issue is the selection of the frequency slot width which may have an impact on the network performance. Last but not least, network dynamicity entails spectrum fragmentation, which significantly reduces the network performance. In this paper we address these topics and, in particular: (1) we present an RSA algorithm to be used in dynamic network scenarios, (2) we study the optimal slot width as a function of the foreseen traffic to be served, and (3) we propose an algorithm to reallocate already established optical connections so that to make room in the spectrum for the new ones. Exhaustive simulation results reveal that the proposed approach improves the blocking probability performance in flexgrid optical networks.

Survivable IP/MPLS-Over-WSON Multilayer Network Optimization

Network operators are facing the problem of dimensioning their networks for the expected huge IP traffic volumes while keeping constant or even reducing the connectivity prices. Therefore, new architectural solutions able to cope with the expected traffic increase in a more cost-effective way are needed. In this work, we study the survivable IP/multi-protocol label switching (MPLS) over wavelength switched optical network (WSON) multilayer network problem as a capital expenditure (CAPEX) minimization problem. Two network approaches providing survivability against optical links, IP/MPLS nodes, and opto-electronic port failures are compared: the classical overlay approach where two redundant IP/MPLS networks are deployed, and the new joint multilayer approach which provides the requested survivability through an orchestrated interlayer recovery scheme which minimizes the over-dimensioning of IP/MPLS nodes. Mathematical programming models are developed for both approaches. Solving these models, however, becomes impractical for realistic networks. In view of this, evolutionary heuristics based on the biased random-key genetic algorithm framework are also proposed. Exhaustive experiments on several reference network scenarios illustrate the effectiveness of the proposed approach in minimizing network CAPEX.

Is multilayer networking feasible

IP traffic has been growing every year, bringing the need for deploying an IP backbone interconnected by links provided by the transport network. Thus, network operators have had traditionally divided their core network in two, the IP network and the transport network. Network planning and engineering tasks have been performed independently in both domains. Traditionally, the transport network has been quite inflexible, and changes have often required a long time to occur. However, recent developments in the control plane allow flexibility in the transport network, making it possible to set up and tear down circuits on demand. In this light, multilayer traffic engineering has been proposed to jointly manage both IP and transport layers, with the aim of optimizing the use of resources. This paper aims to describe the rationale behind multilayer traffic engineering, demonstrate its feasibility and quantify its advantages in terms of cost effectiveness. Also, this work takes a look at the different choices in performing the multilayer operation, in terms of control plane implementation and equipment integration. Finally, the paper presents a report on multilayer traffic engineer experimentation which proves its feasibility and show a preliminary techno-economic case study of the multilayer operation.

Finding the target cost for sliceable bandwidth variable transponders

Elastic optical networking (EON) is a solution that promises to improve infrastructure utilization by implementing flexible spectrum allocation with small spectrum slots instead of the rigid 50 GHz fixed grid of current dense wavelength division multiplexing deployments. This new EON flexible grid supports bandwidth variable transponders (BVTs) that can tune their bit rate and bandwidth dynamically with a trade-off between reach and capacity. However, when BVTs need to transmit at low bit rates, part of their capacity is wasted. Therefore, the sliceable bandwidth variable transponder (SBVT) has been proposed, which can provide even higher levels of elasticity and efficiency to the network. SBVTs enable transmitting from one point to multiple destinations, changing the traffic rate to each destination and the number of destinations on demand. The aim of this work is to identify the target cost of 400 Gb/s and 1 Tb/s SBVTs to reduce, by at least 50%, transponder costs in a core network scenario. This target cost is calculated in relation to estimations for BVTs of 400 Gb/s and 1 Tb/s (non-sliceable). In light of our results, cost savings of 50% are feasible for 1 Tb/s transponders until 2020 with a higher cost than non-sliceable transponders. Savings of 50% for the 400 Gb/s case are possible in the short-term before 1 Tb/s SBVTs can appear in the market. Feasibility of such savings with a target cost higher than current non-sliceable transponders shows that SBVTs can be a reality. Moreover, this work assesses the IP port savings thanks to the utilization of the SBVTs.

A service-oriented hybrid access network and clouds architecture

Many telecom operators are deploying their own cloud infrastructure with the two-fold objective of providing cloud services to their customers and enabling network function virtualization. In this article we present an architecture we call SHINE, which focuses on orchestrating cloud with heterogeneous access and core networks. In this architecture intra and inter DC connectivity is dynamically controlled, maximizing the overall performance in terms of throughput and latency while minimizing total costs. The main building blocks are: a future-proof network architecture that can scale to offer potentially unlimited bandwidth based on an active remote node (ARN) to interface end-users and the core network; an innovative distributed DC architecture consisting of micro-DCs placed in selected core locations to accelerate content delivery, reducing core network traffic, and ensuring very low latency; and dynamic orchestration of the distributed DC and access and core network segments. SHINE will provide unprecedented quality of experience, greatly reducing costs by coordinating network and cloud and facilitating service chaining by virtualizing network functions.

The need for a Control Orchestration Protocol in research projects on optical networking

The Control Orchestration Protocol (COP) abstracts a common set of control plane functions used by an various SDN controllers, allowing the interworking of heterogeneous control plane paradigms (i.e., OpenFlow, GMPLS/PCE). COP has been defined using YANG model language and can be transported using RESTconf, which is being incorporated by industry. COP has been defined in the scope of STRAUSS due to the need for an overarching control plane protocol for network orchestration. In this paper, several research projects describe how the COP could fit in their architecture and propose a use case for COP usage. The proposed COP use cases cover the following research projects: STRAUSS, IDEALIST, DISCUS, COMBO, INSPACE.

Elastic optical networking: An operators perspective

Although there is perhaps an acceptance that EON has benefits, there is a debate about whether a full flexgrid implementation is required to achieve those benefits. Current industry debate addressed in this paper relates to when is the most appropriate time for carriers to: (a) install flexgrid ready components, and (b) enable them and start using the technology.

SDN orchestration of OpenFlow and GMPLS flexi-grid networks with a stateful hierarchical PCE [invited]

New and emerging use cases, such as the interconnection of geographically remote data centers, are drawing attention to the need for provisioning end-to-end connectivity services spanning multiple and heterogeneous network domains. This heterogeneity is due not only to the data transmission and switching technology (the so-called data plane) but also to the deployed control plane, which may be used within each domain to automate the setup and recovery of such services, dynamically. The choice of a control plane is affected by factors such as availability, maturity, operators preference, and the ability to satisfy a list of functional requirements. Given the current developments around OpenFlow and software-defined networking (SDN) along with the need to account for existing deployments based on GMPLS, the problem of heterogeneous control plane interworking needs to be solved. The retained solution must equally address the specific issues of multidomain networks, such as limited domain topology visibility, given the scalability and confidentiality constraints that characterize them. In this setting, we propose a functional and protocol architecture for such interworking, based on the key concepts of network abstraction and overarching control, implemented in terms of a hierarchical stateful path computation element (PCE), which provides the orchestration and coordination layer. In the proposed architecture, the PCEP and BGP-LS protocols are extended to support OpenFlow addresses and datapath identifiers, unifying both GMPLS and OpenFlow domains. The solution is deployed in an experimental testbed and validated. Although the main scope of the approach is the interworking of OpenFlow and GMPLS, the same approach can be directly applied to a wide range of multidomain scenarios, with either homogeneous or heterogeneous control technologies.

OpEx savings by reduction of stock of spare parts with Sliceable Bandwidth Variable Transponders

This work analyses the OpEx savings related to stock of spare parts for Sliceable Bandwidth Variable Transponders versus traditional fixed rate transponders. Target cost of sliceable transponders based on these OpEx savings is obtained.

Experimental Demonstration of Multivendor and Multidomain EON With Data and Control Interoperability Over a Pan-European Test Bed

The operation of multidomain and multivendor EONs can be achieved by interoperable sliceable bandwidth variable transponders (S-BVTs), a GMPLS/BGP-LS-based control plane, and a planning tool. The control plane is extended to include the control of S-BVTs and elastic cross connects, which combine a large port-count fiber-switch (optical backplane) and bandwidth-variable wavelength-selective switches, enabling the end-to-end provisioning and recovery of network services. A multipartner testbed is built to demonstrate and validate the proposed end-to-end architecture. Interoperability among S-BVTs is experimentally tested between different implementations. In this case, transponders are configured using the proposed control plane. The achieved performance with hard-decision and soft-decision FECs using only the information distributed by the control plane is measured against the performance of the single-vendor implementation, where proprietary information is used, demonstrating error-free transmission up to 300 km.