M. Dallaglio

Routing, Spectrum, and Transponder Assignment in Elastic Optical Networks

Backbone networks are evolving toward elastic optical network (EON) architecture that allows a flexible and efficient use of spectrum resources. Flexibility in EONs is also guaranteed by emerging sliceable bandwidth variable transponders (SBVTs) that support the simultaneous generation of multiple optical carriers. Such carriers can be used to serve different lightpaths (i.e., slice-ability), or can be merged into a single high-rate superchannel. SBVTs typically use a dedicated laser to generate each carrier, i.e., multilasers SBVT (ML-SBVT). Alternatively, a multiwavelength source can be used to generate multiple carriers using a single laser, i.e., multiwavelength SBVT (MW-SBVT). MW-SBVT improves the super-channel spectrum efficiency. Indeed, MW-SBVT reduces the intercarrier interference among the subcarriers composing the super-channel; thus, it is possible to reduce the guard bands among subcarriers. With ML-SBVT, each subcarrier suffers from unstableness of the related laser and intercarrier interference may have a huge impact, thus, higher guard bands are needed. On the other hand, the use of a MW-SBVT introduces specific constraints to the routing and spectrum assignment (RSA), because the spacing among the subcarriers is limited to a range of specific values. To take into account the constraints introduced by transponders, this paper integrates the selection of the transponder into RSA; thus, proposing a dynamic routing, spectrum, and transponder assignment (RSTA) scheme supporting both ML-SBVT and MW-SBVT technologies, and aiming to combine the benefits of the two technologies. Simulation results show that the proposed RSTA scheme provides benefits in terms of achieved blocking probability compared to the traditional RSA schemes. Moreover, the achieved results demonstrate that jointly using both SBVT technologies provides significant benefits with respect to the utilization of any single SBVT technology.

Impact of SBVTS based on multi wavelength source during provisioning and restoration in elastic optical networks

Slice-ability provided by SBVTs is exploited in EONs to increase provisioned and recovered traffic. SBVTs based on multi-wavelength sources are subject to additional constraints but increase spectrum efficiency. We evaluate the impact of those SBVTs during both provisioning and restoration.

YANG model and NETCONF protocol for control and management of elastic optical networks

This paper proposes a YANG model to describe a sliceable transponder with variable rate, code, modulation formats, and monitoring capabilities. The model is introduced into NETCONF, which is experimentally demonstrated in a testbed.

Provisioning and restoration with sliceability in GMPLS-based elastic optical networks [Invited]

Multiflow bandwidth variable transponders supporting sliceability enable effective use of node and spectrum resources in elastic optical networks (EONs). Specifically, such transponders are capable of creating multiple optical flow units (i.e., subcarriers) that can be aggregated or independently routed according to the traffic requirements. This paper investigates the utilization of sliceability during provisioning and restoration in EONs. Specifically, a scheme is proposed to exploit the possibility of establishing/recovering an optical connection as a single superchannel or as a number of independent subcarriers. To this end the spectrum overbuild introduced by the sliceability application has to be taken into account. Both centralized and distributed implementations of the proposed schemes are evaluated in a generalized multiprotocol label switching (GMPLS)-based EON. Simulations show that despite the introduced spectrum overbuild, the utilization of sliceability permits us to significantly increase the amount of established/recovered traffic. Moreover, simulations show that the blocking probability reduction is achieved with only a slight increase in the setup time.

Add and drop architectures for multi-carrier transponders in EONs

The elastic optical network (EON) is a paradigm for optical networks, based on the combination of a flexible grid, advanced transmission techniques, and bandwidth-variable optical switching. Recent studies on EONs have been focused on multi-carrier transponders with coherent detection. Such transponders can achieve high-rate (e.g., 1 Tb/s) lightpaths through super-channels. A particular case of the multi-carrier transponder is the sliceable bandwidth variable transponder (S-BVT) where the generated flows can also be routed onto different paths and toward different destinations. The add and drop (A&D) module connecting transponders to the optical cross connect plays an important role in the design of the network node. In particular, depending on the A&D architecture, the flexibility provided by the multi-carrier transponder and the S-BVTs may be partially limited. This paper gives first a technological overview of different A&D architectures. In particular, the coupler/splitter, multicast switch, and wavelength-selective switch technologies for A&D are reviewed. Then, we investigate how different A&D architectures influence the benefit of elastic spectral efficiency in a long-haul meshed network scenario, looking for a trade-off between costs and performance.

On the Add & Drop architecture for S-BVTs in EONs

The matching between Add&Drop (A&D) and S-BVT in EONs is investigated. Two A&D architectures have been identified avoiding or not channel contentions. A trade-off between costs and flexibility can be found depending on the status of the network.

Control and management of transponders with NEDCONF and YANG

The continuous evolution of elastic optical networks (EONs) toward more efficient and flexible backbone networks has been enabled by the innovation of data and control plane technologies. Network Configuration Protocol (NETCONF) is emerging as a software-defined networking (SDN) protocol for the control of optical networks. Its relevance is due to the fact that, besides providing control functionalities (e.g., data plane device configuration), NETCONF also provides management functionalities (e.g., access to monitoring information). NETCONF may exploit the Yet Another Next Generation (YANG) data model to describe network elements to be controlled/managed. YANG and NETCONF are of interest for operators since they provide a standard way to control and manage network elements independently from the vendor. This paper presents and demonstrates a control and management plane for EONs, based on the NETCONF protocol and YANG. In particular, a YANG model describing optical transponders supporting sliceability, variable rate, and monitoring functionalities is proposed. NETCONF experimental demonstrations are carried out to validate the proposed model and to prove the control and management capabilities of these technologies when applied to EONs.

Management of sliceable transponder with NETCONF and YANG

NETCONF is emerging as Software Defined Networking (SDN) protocol for the control and management of optical networks. It enables data plane device configuration and access to monitoring information. NETCONF may exploit YANG data model to describe network elements to be controlled/managed. YANG and NETCONF are of interest for operators since they provide a standard way to control and manage network elements, independently from the vendor. This paper presents and demonstrates a management plane based on NETCONF protocol. In particular, a YANG model describing optical transponders supporting slice-ability, variable rate, and monitoring functionalities is proposed. NETCONF experimental demonstrations are carried out to validate the proposed model and to prove the control and management capabilities of these technologies applied to elastic optical networks (EONs).

Control and management of VCSEL-based transmission in intra-data centers

We demonstrate a software-defined reconfigurable VCSEL-based transponder for intra-data centers. NETCONF messages are reported for control and management in uncooled and cooled scenarios together with performance at varying environment conditions.

YANG Models for Vendor-Neutral Optical Networks, Reconfigurable through State Machine

Multi-vendor interoperability can be achieved at node and network levels by relying on standard data modeling. YANG represents an attractive data modeling solution for network component definition. This article reports on the work done on YANG models for optical networks with particular reference to flexible-grid networks. In addition to a YANG model description for link, node, and media channels, YANG for a sliceable transponder is introduced given the importance of such a data plane device for the next generation backbone. Then a contribution is provided in proposing YANG models for events and state machine to further extend and increase the programmability of networks. This latter contribution is particularly relevant in the case of faults or physical layer degradation in a network. Finally, YANG models are validated in an experimental control plane testbed.