In that serves as the base research carried out

In this chapter, we present vitally related work documentation that serves as the base research carried out related to our problem. Here are described various approaches that look for implementation techniques oriented towards the creation of access services for subscribers. Some implementations emerge from the concepts of NFV and propose distributed systems adapted from classical network architectures, meanwhile, others provide approaches on implementation based on SDN. The common objectives of each approach mainly focus on reducing the complexity of classical access service delivery technologies, which as explained before are highly expensive and unable to properly provide a distribution of services avoiding single point of failure in the network for the provided services.SDN and OpenFlow become in a broad field of research that aims to the improvement of classical carrier networks. ISPs are eager regarding BRAS system operation evolution, willing to align current implementations with the benefits that NFV/SDN provide. The Split Architecture (SPARC-FP7) project is one of those SDN-based works. It has taken the lead in proposing a splitting architecture from classical networks towards a fully operational SDN architecture. It studies the carrier-grade extensions such as reliability, OAM, network virtualization and resource isolation in order to provide a separated architecture in which each extension could be further developed without being slowed down by the others. Next sections present first the distributions strategies based on control and data plane isolation, later on, approaches based on SDN Split Architecture and concluding with the virtualized network functions across different platforms. Additional function oriented implementations are considered important for this thesis and therefore included afterwards.This section shows implementation proposals which target the creation of access services through the use of SDN as the network architecture. In citep{ruckert2014flexible} a new traffic management architecture based on SDN is proposed. It aims to extend the classical broadband network architecture, modifying the traffic management to improve the efficiency of the traffic in the ISP’s network. To this end, it proposes to enable SDN functionalities on end-user devices i.e. in home gateways (HGW). By doing so, a flexible and dynamic configuration of the traffic flows in the network is achieved. To test the solution, it performs a proof of concept that needs to adapt a BRAS platform. The implemented BRAS system fits two main characteristics: first, customer tunneling for sessions termination and second, communication with the SDN controller for session state updates (BRAS control plane and data plane communication). The system provides access services to the HGW and installs the respective entries in each equipment which compose the network path from the access to the core network. Additionally, it provides a flexible configuration of services such as content delivery networks to let the traffic access distributed content directly without the need to forwarding the traffic until the edge of the core network. The project in citep{osborne2014investigation} addresses the weaknesses and vulnerabilities of classical centralized models for access services provision. It implements a basic system which provides resource allocation and customer tunneling based on SDN and OpenFlow. For the session establishment, it implements a protocol sequence which involves the whole BRAS system (BRAS control plane, data plane and external services functionalities). Along with the session establishment, a dynamic flow creation in the data path elements is presented which is adapted from the OpenFlow operation. It extracts special packet header options and information from a subscriber database as a result of the session registration to provide the dynamic flow creation.In general, solutions based on SDN architecture procure to provide access service creation taking into account the advantages that SDN offer. They intend to decentralize and distribute the service creation points in the provider network and so, reducing single point of failure for the given services. However, when referring to SDN, the dependence of a centralized control still remains, among others, due to the still young evolution and ongoing adjustments of the system. It leads to a series of constraints, especially when looking at the creation of access services point of view. This is evidenced by the fact that a number of distinct requests are received from the customer side. Due to that reason, the amount of traffic flowing towards the controller is significantly large and the installed entries on the data path elements may vary extremely which have unfavorable repercussions in the performance of the network.