Multi-layer Transport Network Slicing with Hard and Soft Isolation A. Alcal ´ a 1 , S. Barguil 1 , V. L´ opez 2 , L.M. Contreras 2 , C. Manso 3 , P. Alemany 3 , R. Casellas 3 , R. Mart´ ınez 3 , D. Gonz´ alez-P´ erez 4 , X. Liu 4 , J.M. Pulido 4 , J.P. Fern´ andez-Palacios 2 , R. Mu ˜ noz 3 , R. Vilalta 3 1 Universidad Aut´ onoma de Madrid, Madrid, Spain 2 Telef´ onica I+D, Madrid, Spain 3 Centre Tecnol` ogic de Telecomunicacions de Catalunya (CTTC/CERCA), Castelldefels (Barcelona), Spain 4 Volta Networks, Barcelona, Spain e-mail: ricard.vilalta@cttc.es Abstract: We validate the deployment of isolated transport network slices in IP over DWDM network. To this end, an isolated transport network slice is deployed using multi-layer isolation mechanisms based on OpenConfig and ONF Transport API. ©2021 The Authors. 1. Introduction The provisioning of connectivity services that guarantee a specific set of Service Level Objectives (SLO) regarding network resources is expected to benefit many use cases, such as beyond 5G networks or NFV and data center inter- connects. Transport network slices provide connectivity coupled with a set of specific network resources commitment between several endpoints over a shared network infrastructure [1]. Each slice is associated with a tenant. Each tenant can control and manage all its slices. As underlying resource multi-tenancy is supported, multiple isolation options are provided, such as soft slicing and hard slicing. Soft network slicing focuses on QoS mechanisms that provide a dynamic allocation of available network resources to different traffic classes. An example of a soft network slice is a VLAN assigned to a customer to carry voice/data traffic, usually transported by LxVPNs. On the other hand, hard network slicing provides component virtualization and replication. An example of a hard network slice is routers (physical or virtual) under the same administrative domain, where services are configured between routers. The virtualization of the transport network can be exploited at the time of provisioning and orchestrating the virtual- ized service functions of the slice [2]. The idea leverages on the concept of Wide-area Infrastructure Manager (WIM) as defined by the ETSI NFV architecture as the element devoted to manage the virtualization capabilities in the WAN. Thus, it is assumed that a control entity will be in charge of handling the WAN transport connectivity for interconnect- ing given communication end-points. When referring to slices, such an entity could be associated to a Network Slice Controller (NSC), as defined in [1] either complementing or being part of an overarching SDN transport network con- trol environment. A single transport network slice request can be decomposed into multiple control and management steps across all the network components involved. In order to provide the necessary transport network slice, NSC will determine the necessary resources allocation depending on the characteristics of the requested network slice (i.e., soft or hard). Once resources are allocated, they are configured on the network using multiple southbound interfaces (SBI). an example interface between the NSC and the underlying optical controller is the Open Networking Foundation (ONF) Transport API (T-API) [3], which allows the underlying optical SDN controller topology export and connec- tivity service provisioning. ONF T-API allows the provisioning of connectivity services with specific connectivity constraints (including QoS requirements), which can later be mapped to specific network slice isolation levels. Another well demonstrated data model is OpenConfig [4], which provides vendor-neutral YANG data models for various network elements, from routers to optical switches. The IP SDN Domain Controller will be responsible for allocating, instantiating and configuring the multiple (virtual) routers and interfaces depending on the required slice isolation level. OpenConfig data models usage is combined with several protocols such as gRPC or NETCONF. The gRPC protocols provide high performance and scalability to the proposed architecture. This paper presents an end-to-end architecture to provide transport network slices deployed over multi-layer IP over DWDM networks. Several degrees of isolation (from hard to soft) might be required and implemented in the requested transport network slice. This is the first paper to explore transport network slice isolation using an IP over DWDM network. In order to validate this proposed architecture, we present a proof-of-concept in Telefonica and CTTC Laboratories.