J. P. Fernandez-Palacios

Towards cloud-ready transport networks

This article presents an operators view of the evolution towards a transport network ready to support cloud services, which are hosted in data centers and reachable through the network. This work shows the reasons why current transport networks are not efficiently designed for a cloud environment, and it describes the architecture for a cloud-ready network. To show the feasibility of such a cloud-ready network, we present three experimental validations of the concepts to support our network evolution.

CAPEX study for a multilayer IP/MPLS-over-flexgrid optical network

The ever-increasing Internet Protocol (IP) traffic volume has finally brought to light the high inefficiency of current wavelength-routed over rigid-grid optical networks in matching the client layer requirements. Such an issue results in the deployment of large-size, expensive, and power-consuming IP/Multi-Protocol Label Switching (MPLS) layers to perform the required grooming/aggregation functionality. To deal with this problem, the emerging flexgrid technology, allowing for reduced-size frequency grids (usually referred to as frequency slots), has recently attracted much attention among network operators, component and equipment suppliers, and the research community. In this paper, we tackle the multilayer IP/MPLS-over-flexgrid optimization problem. To this end, an integer linear programing formulation and a greedy randomized adaptive search procedure (GRASP) metaheuristic are provided. Using GRASP, we analyze the cost implications that a set of frequency slot widths have on the capital expenditure investments required to deploy such a multilayer network. For the sake of a compelling analysis, exhaustive numerical experiments are carried out considering a set of realistic network topologies, network equipment costs, and traffic instances. Results show that investments in optical equipment capable of operating under slot widths of 12.5 GHz, or even 25 GHz, are more appropriate, given the expected traffic evolution.

Planning fixed to flexgrid gradual migration: drivers and open issues

Flexgrid technology has recently been presented as the most promising option for upgrading the currently operating fixed grid optical networks and extending their capacity to be able to deal with the massive traffic volumes forecast for the next decade. Although the current traffic is successfully supported on fixed grid networks, flexgrid technology brings features that are not offered by the fixed grid networks, such as transporting optical connections with a capacity beyond 100 Gb/s and elasticity against time-varying traffic. In light of this, a gradual fixed grid to flexgrid migration is generally accepted in order to add these useful features to the network. In this article, we study the migration process where flexgrid is deployed in the network progressively, and review the main drivers and open issues induced by its deployment.

Cross-stratum orchestration and flexgrid optical networks for data center federations

Current inter-data-center connections are configured as static big fat pipes, which entails large bit rate over-provisioning and thus high operational costs for DC operators. On the other hand, network operators cannot share such connections between customers, because DC traffic varies greatly over time. Those connections are used to perform virtual machine migration and database synchronization among federated DCs, allowing elastic DC operations. To improve resource utilization and save costs, dynamic inter-DC connectivity is currently being targeted from a research point of view and in standardization form. In this article, we show that dynamic connectivity is not enough to guarantee elastic DC operations and might lead to poor performance provided that not enough overprovisioning of network resources is performed. To alleviate it to some extent, we propose using the flexgrid optical technology that enables finer spectrum granularity adaptation and the ability to dynamically increase and decrease the amount of optical resources assigned to connections. DCs can be interconnected through a flexgrid-based network controlled using a centralized software defined network, based on the architecture currently being proposed by the IETF; a cross-stratum orchestrator architecture coordinates DC and network elastically. Illustrative results show that dynamic elastic connectivity provides benefits by reducing the amount of overprovisioned network resources and facilitating elastic DC operations.

Path computation element in telecom networks: Recent developments and standardization activities

This paper provides an overview of the recent developments in research and the IETF standardization body on using a path computation element in complex telecom networking scenarios such as the multi-layer and multi-domain cases. Implications on the control plane when using such element are addressed as well as the required protocol extensions. The emerging impairment-aware routing and wavelength assignment problem is extensively treated for networks using lightpaths.

Demonstration of low latency Intra/Inter Data-Centre heterogeneous optical Sub-wavelength network using extended GMPLS-PCE control-plane

This paper reports on the first user/application-driven multi-technology optical sub-wavelength network for intra/inter Data-Centre (DC) communications. Two DCs each with distinct sub-wavelength switching technologies, frame based synchronous TSON and packet based asynchronous OPST are interconnected by a WSON inter-DC communication. The intra/inter DC testbed demonstrates ultra-low latency (packet-delay <270 µs and packet-delay-variation (PDV)<10 µs) flexible data-rate traffic transfer by point-to-point, point-to-multipoint, and multipoint-to-(multi)point connectivity, highly suitable for cloud based applications and high performance computing (HPC). The extended GMPLS-PCE-SLAE based control-plane enables innovative application-driven end-to-end sub-wavelength path setup and resource reservation across the multi technology data-plane, which has been assessed for as many as 25 concurrent requests.

IP offloading over multi-granular photonic switching technologies

This paper introduces and demonstrates the technical feasibility of a new network architecture where Internet traffic between IP accesses (BRAS) and inter-carrier interconnection nodes is exclusively transported over multi-granular photonic switching technologies without any intermediary transit IP packet processing.

Assessment of flexgrid technologies in the MAN for centralized BRAS architecture using S-BVT

We numerically analyze a flexgrid metro network scenario identifying the requirements for BRAS centralization. A cost-effective S-BVT architecture based on MB-OFDM and DD with DSP-enabled software-defined flexible/adaptive capabilities is proposed and experimentally evaluated for supporting multiple 10Gb/s connections.

Network virtualization, control plane and service orchestration of the ICT STRAUSS project

Emerging cloud applications such as real-time data backup, remote desktop, server clustering, etc. require not only more traffic being delivered between datacenters, but also dedicated and application-specific virtual optical network (VON) services to support each applications QoS and SLA level. On the other hand, another requirement is to support end-to-end network service provisioning across multiple VONs comprising different transport (e.g. Flexi-grid DWDM OCS, OPS, etc) and control plane technologies (e.g., centralized OpenFlow or distributed GMPLS). This paper presents the preliminary architecture of the network virtualization, control and orchestration layers proposed in the STRAUSS project.

Migration steps toward flexi-grid networks

It is widely acknowledged by operators and market analysts from all parts of the telecommunications industry that bandwidth demand is increasing dramatically, year by year. This traffic growth highly impacts on all network segments and pushes network operators to consider new networking solutions. Flexi-grid technologies enable more flexible use of the spectral resources, increasing the overall network spectral efficiency. However, the currently deployed fixed-grid dense wavelength division multiplexing (DWDM) optical infrastructure might be replaced with new components to enable this technology. This paper first identifies a realistic expectation of modulation formats for the next 10 years and quantifies the possible capacity gains. Second, we study when the capacity will be exhausted using current fixed-grid optical channel assignment, and compare this with a pack of novel evolution strategies toward flexi-grid. Results show that the capacity will be exhausted by 2019 in the Spanish core network, and that by applying the flexi-grid evolutionary model, the network life can be extended up to five years. A shorter-term rationale to migrate to flexi-grid is the availability of cost-effective 400 Gbps and 1 Tbps transmission.