Analysis of end-to-end multi-domain management and orchestration frameworks for software defined infrastructures: an architectural survey <s> Standard activities <s> The idea of programmable networks has recently re-gained considerable momentum due to the emergence of the Software-Defined Networking (SDN) paradigm. SDN, often referred to as a "radical new idea in networking", promises to dramatically simplify network management and enable innovation through network programmability. This paper surveys the state-of-the-art in programmable networks with an emphasis on SDN. We provide a historic perspective of programmable networks from early ideas to recent developments. Then we present the SDN architecture and the OpenFlow standard in particular, discuss current alternatives for implementation and testing of SDN-based protocols and services, examine current and future SDN applications, and explore promising research directions based on the SDN paradigm. <s> BIB001 </s> Analysis of end-to-end multi-domain management and orchestration frameworks for software defined infrastructures: an architectural survey <s> Standard activities <s> NGSON is an IEEE sponsored effort to standardize an open service ecosystem where different stakeholders may cooperate to satisfy users’ ever changing requirements by composing and delivering services dynamically across different service providers and network operators’ domains. A main distinguishing feature of NGSON is context awareness, that is, the capability of collecting, processing, and using context information to drive the interactions of the NGSON overlay nodes with service and network operators’ infrastructures for guaranteeing an optimal user experience. Recent advances in network control and management technologies, such as SDN, NFV, and service-oriented networking paradigms, are expected to make the network effectively able to cope with application service requirements in a more flexible, timely, and agile manner. In this article we discuss how NGSON, which already incorporates several aspects of virtualization, could take advantage of network virtualization mechanisms and programmable traffic steering capabilities to enhance and effectively support context-aware service composition along with adaptive service delivery. We propose an architectural model for NGSON that leverages these novel network service control capabilities and illustrate through a use case how this model could effectively be put into operation. <s> BIB002
This section provides an overview of activities in ETSI, ITU-T and BBF related to E2E MANO. (1) ETSI NFV The ETSI industry specification group for NFV, with representatives from both telecoms and IT vendors, focuses on defining specifications for the virtualisation of functions within telecommunications networks. One major result of ETSI NFV is the definition of the reference functional architecture (Figure 4 ) by the MANO working group  , which focuses on the aspects brought into the operator's networks by NFV. In its recently started phase 2, ETSI NFV activities include more than 30 new work items and aim at producing normative specifications that define the interfaces related to the main reference points in the NFV-MANO architectural framework. During phase 1, the MANO working group deliverables briefly discussed the implications of multiple administrative domains for the reference architecture, as required by some of the proposed use cases [22] . According to  , NFVO is responsible for two major functions: Resource orchestration: orchestration of resources across multiple virtualised infrastructure managers (VIM), and Network service orchestration: life cycle management of NSs. The split of these two functions in separated functional blocks is also envisioned to support use cases in which a multi-domain orchestration of services is a requirement  . However, further detailed discussions were shifted to ETSI NFV phase 2. Some use cases related to the split of NFVO are currently being discussed in  . Especially interesting is the use case entitled 'Network Services offered by a separate admin domain', where an operator is offering NSs that span across multiple administra- tive domains using a so-called umbrella NFVO. This use case introduces a new reference point between NFVOs in different domains. In  , ETSI NFV ISG provides an overview on typical design patterns, use cases, feedback from proof of concepts and recommendations on using SDN in NFV-MANO architectural framework. Some gaps and recommendations for further studying the applicability of the current reference framework to multiple administrative domain scenarios are also highlighted in this document. Many of them refer to the need of specifying an east-west interface between NFVOs for exchanging information on connectivity, offered services, pricing and so on. After phase 1, ETSI NFV ISG members, with the support of the Linux Foundation, started an open source project that aims at delivering a defacto standard NFV platform for the industry, open platform for NFV (OPNFV)  . OPNFV looks to realise the ETSI NFV architectural framework by integrating and extending existing open source projects, such as OpenStack, OpenDaylight, KVM and Open vSwitch, among others. While its first two releases (Arno 2015-06, Brahmaputra 2016-02) focus on resource orchestration, building NFV infrastructure and VIM, OPNFV platform is also expected to cover network service orchestration functions (NFVO) in future releases. (2) ITU-T Recognising the impact that 'softwarisation' is having on ICT industry and what it will mean for the industry of the 5G era, a study group (SG13) dedicated to 'Future networks including cloud computing, mobile and next-generation networks' [25] at ITU-T focuses on FNs and SDN within. The group is standardising FNs with the objectives of service (network virtualisation), data, environmental (energy saving for FNs) and socio-economic awareness. Their plans are to develop different facets of the smart ubiquitous network, requirements of network virtualisation for FNs, framework of telecom SDN and requirements of formal specification and verification methods for SDN. The group also develops standards that detail requirements and functional architectures of the cloud computing ecosystem, covering inter-cloud and intra-cloud computing and technologies supporting everything-as-a-service. This work includes infrastructure and networking aspects of cloud computing models, as well as deployment considerations and requirements for interoperability and data portability. Given that cloud computing relies on the interplay of a variety of telecom and IT infrastructure resources, SG13 develops standards enabling consistent E2E, multi-cloud management and monitoring of services exposed by and across different SPs' domains and technologies [26] . SG13 published a recommendation in 2015 on resource management in (multi) cloud computing: the recommendation presents general concepts of E2E resource management cloud services, a vision for adoption of cloud resource management in a telecommunication-rich environment [27] . Within SG13, there is a focus group on network aspects of IMT-2020 (international mobile telecommunications)  that was established in May 2015 to analyse how emerging 5G technologies will inter-act in FNs. The group took an ecosystem view of 5G research of development and published a preliminary study  on the networking innovations required to support the development of 5G systems. It has proposed a high level-5G architecture based on the analysis of the 5G requirements, which will be more elaborated in the standardisation phases. It also proposed and elaborated the new concept of Network softwarisation that is represented an overall transformation trend for designing, implementing, deploying, managing and maintaining network equipment and network components by software programming, exploiting characteristics of software such as flexibility and rapidity of design, development and deployment throughout the life cycle of network equipment and components, for creating conditions that enable the redesign of network and services architectures; allow optimisation of costs and processes; and enable self-management. The focus group continues to work on the challenges that telecoms players must overcome in the development of the 5G ecosystem. Specific tasks and areas of work include refining their IMT-2020 network architecture, prototyping (preferably with the open-source community) network softwarisation and information-centric networking, studying network slicing for the fronthaul/backhaul network and defining new traffic models and associated aspects of QoS and operations, administration and management applicable to IMT-2020 networks. Another study group, SG11 (protocols and test specifications) released a closely related recommendation on the signalling requirements for flexible NS deployments [30] : the recommendation describes the signalling requirements, based on the service platform broadband network gateway (BNG) architecture, needed to achieve outstanding benefits like easy deployment of fine-grained NS. The three aspects the recommendation covers are NS combination/orchestration, service configuration on the BNG, and BNG resources, status and event notification to the service platform. (3) BBF There are several ongoing activities within broadband forum (BBF) that is related to the MANO plane of telecommunication networks. The architecture and migration work area at BBF identifies the relationships between entities to facilitate the transition of networks towards virtualisation while documenting the key functionalities that need to be brought forward to enable a seamless evolution path. The work underpins all the new valueadded services and application delivery for fixed and mobile access networks, home and business that can now be deployed at the pace of each market. The models reflect the control, management and data plane aspects of BBF defined architectures and are augmented to subsume new industry directions such as SDN and NFV while carrying forward key aspects of broadband as currently deployed. The work on defining an SDN reference model contains a working text (WT-370) that investigates on the technical aspects associated with fixed access network sharing, addressing the typical infrastructures, topologies and deployment scenarios. It also provides security considerations necessary to support multi-operator access sharing. Besides multioperator sharing scenarios, this project can be also appropriate for a network operator that wants to slice its access network to offer different services towards customers (e.g. for residential or enterprise markets) and wants to be able to manage it using a vertical organisation structure [31] . The SDN and NFV Work area at BBF focuses on the migration of SDN and NFV, and on the coexistence of physical and virtual elements in the broadband network. The former facilitates agile deployment of new customised distributed broadband services and applications. This, in turn, enables new revenues and provider differentiation while managing OpEx both in the access network and in single-tenant, and multi-tenant residential and business locations. Among other initiatives, the virtual business gateway working text (WT-328) specifies architecture and requirements for the migration of functionalities running on a business gateway to the network SP's infrastructure for enabling networkbased features and services. Such migration is expected to simplify the deployment and management of the network and business services [31] . Broadband forum has also produced a white paper on wholesaling network access [32] : the open access principles with respect to the network infrastructure are translated into the support of wholesale services to enable downstream retail SPs to leverage and share the next-generation access investments. (4) IEEE next-generation service overlay network (NGSON) IEEE NGSON  is a reference framework as presented in Figure 5 for the control and delivery of composite services over diverse IP-based networks with QoS support. As a service overlay network, the NGSON acts as an intermediate layer to support the creation and deployment of composite services across different SPs and over heterogeneous network domains. With respect to prior self-organised networks, NGSON makes progress in the provision of services to end users with better quality of experience by customising and adapting composite services to the dynamic context of users, devices, services and networks while optimising network and computing resources consumption. Cloud technologies for virtualisation of network and computing resources are also expected to enforce this vision. The NGSON functional architecture includes servicerelated functions, transport-related functions, and operation and management functions. The service-related functions include functions that relate to the service control operations, that is, service registry, service discovery, service composition and service routing. The transport-related functions support service data delivery and include network context-aware routing, traffic optimisation, resource scheduling and interworking with underlying networks through dynamic policy enforcement. Operation and management functions are also supported such as service management, life cycle management and service assurance [34] . At service level control, NGSON manages the service information (i.e. functional description and QoS capabilities) published by third-party SPs collected in the service registry. As an end-user requests a service, the service discovery function use the service registry to select and negotiate an appropriate service instance that fulfils the user's demands on the functions and properties of the target service. Based on the binding information of the selected service instance, the service routing function conveys the service request to the selected service and invokes it for service. NGSON also orchestrates a series of the service interactions among one or more component services as specified in the service composition specification. NGSON integrates service-aware technologies supported by service oriented architecture  with service components deployed in heterogeneous systems while exploiting context information and adaptation features to dynamically (re-)accommodate service components and their interactions. For the service delivery, NGSON extracts the requirements for service-and transport-related QoS to enforce corresponding QoS control mechanisms across the underlying networks. Software-defined networking BIB001 and NFV  initiatives can significantly contribute to achieve greater elasticity in NS deployments and accelerate a prominent innovation in NGSON service provisioning and delivery functions. In particular, SDN and NFV allow SPs to create a more powerful service logics based on NGSON that include VNFs handled as service components and participating to the service composition and orchestration process BIB002 . In this regard, initiatives in IEEE and in NGSON WG have been recently undertaken to identify potential new standards in SDN/NFV and related areas to be developed in IEEE.