Oscar Gonzalez de Dios

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.

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 Assessment of ABNO-Driven Multicast Connectivity in Flexgrid Networks

The increasing demand of internet services is pushing cloud services providers to increase the capacity of their data centers (DC) and create DC federations, where two or more cloud providers interconnect their infrastructures. As a result of the huge capacity required for the inter-DC network, the flexgrid optical technology can be used. In such scenario, applications can run in DCs placed in geographically distant locations, and hence, multicast-based communication services among their components are required. In this paper, we study two different approaches to provide multicast services in multilayer scenarios assuming that the optical network is based on the flexgrid technology: 1) establishing a point-to-multipoint optical connection (light-tree) for each multicast request, and 2) using a multipurpose virtual network topology (VNT) to serve both unicast and multicast connectivity requests. When that VNT is not able to serve an incoming request as a result of lack of capacity, it is reconfigured to add more resources. A control plane architecture based on the applications-based network operations (ABNO) one, currently being standardized by the IETF, is presented; workflows are proposed and PCEP extensions are studied for the considered approaches. The experimental validation is carried-out on a testbed setup connecting Telefonica, CNIT, and UPC premises.

A GRASP with path-relinking heuristic for the survivable IP/MPLS-over-WSON multi-layer network optimization problem

In this paper we deal with the survivable internet protocol (IP)/multi-protocol label switching (MPLS)-over-wavelength switched optical network (WSON) multi-layer network optimization problem (SIMNO). This problem entails planning an IP/MPLS network layer over a photonic mesh infrastructure whilst, at the same time, ensuring the highest availability of services and minimizing the capital expenditures (CAPEX) investments. Such a problem is currently identified as an open issue among network operators, and hence, its solution is of great interest. To tackle SIMNO, we first provide an integer linear programming (ILP) formulation which provides an insight into the complexity of its managing. Then, a greedy randomized adaptive search procedure (GRASP) with path-relinking (PR) together with a biased random-key genetic algorithm (BRKGA) are specifically developed to help solve the problem. The performance of both heuristics is exhaustively tested and compared making use of various network and traffic instances. Numerical experiments show the benefits of using GRASP instead of BRKGA when dealing with highly complex network scenarios. Moreover, we verified that the use of GRASP with PR remarkably improves the basic GRASP algorithm, particularly in real-sized, complex scenarios such as those proposed in this paper.

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.

Window-based burst assembly scheme for TCP traffic over OBS

The impact of burstification delay on the transmission control protocol traffic statistics is presented as well as a new assembly scheme that uses flow window size as the threshold criterion. It is shown that short assembly times are ideally suitable for sources with small congestion windows, allowing for a speedup in their transmission. In addition, large assembly times do not yield any throughput gain, despite the large number of segments per burst transmitted, but result in a low throughput variation, and thus a higher notion of fairness among the individual flows. To this end we propose a new burst assembly scheme that dynamically assigns flows to different assembly queues with different assembly timers, based on their instant window size. Results show that the proposed scheme with different timers provides a higher average throughput together with a smaller variance, which is a good compromise for bandwidth dimensioning.

TCP traffic analysis for timer-based burstifiers in OBS networks

The purpose of this paper is to assess the impact of timer-based burst assembly algorithms for TCP traffic. We present an analysis for short, medium and long assembly times and investigate segment and flow distribution over the assembled bursts. Further, we also analyze their impact on the congestion window evolution and on the effective throughput achieved. It has been found out that short assembly times are ideally suitable for sources with small congestion windows, allowing for a speed up, while large assembly times yield a lower throughput variation among the individual assembled flows. For long assembly times, the transfer of more segments from the same source is trading off the increase of the burstification delay but no throughput gain is obtained. However, large assembly times smooth out individual flow performance and provide a significant lower variation of throughput. To this end, in this paper, we propose a new adaptive burst assembly algorithm that dynamically assigns flows to different burstifiers based on their instant window size.

Utilization of temporary reservation of path computed resources for multi-domain path computation element protocols in WDM networks

In recent years, Path Computation Element (PCE) architecture has been standardized as a suitable solution for path computation in multi-domain network scenarios. The Traffic Engineering Database (TED) of the PCE is updated with the information of the control plane. However, there is a delay from the PCE replies to a request, until the TED is updated with the network status information. This delay includes not only the control plane delay, but also Path Computation Element Protocol (PCEP) information exchange. This desynchronization in the TED and the real status information leads to an extra blocking situation when the Label Switch Router (LSR) tries to reserve a path, but it has been previously reserved by other LSR. To solve such problem, a recent draft is submitted to the IETF proposing new PCEP extensions for a pre-reservation of the computed path resources for a certain period. This work implements in C three multi-domain algorithms: Per-domain Path Computation, Backward-Recursive PCE-based Computation and Hierarchical Path Computation Element and it assesses their performance with and without mechanisms to reduce this extra blocking probability due to the uncertainty of the TED information.