Abstract
A diversity of technical advances in the field of network and systems virtualization have made it possible to consolidate and manage resources in an unprecedented scale. These advances have started to come out of the data centers, spreading towards the network service provider (NSP) and telecommunications operator infrastructure foundations, from the core to the edge networks, the access network, and the customer premises LAN (local area network). In this context, the residential gateway (RGW) constitutes an ideal candidate for virtualization, as it stands between the home LAN and the access network, imposing a considerable cost for the NSP while constituting a single point of failure for all the services offered to residential customers. This chapter presents the rationale for the virtual RGW (vRGW) concept, providing an overview of past and current implementation proposals and discussing how recent technological developments in key areas such as networking and virtualization have given a competitive edge to a RGW virtualization scenario, when compared with traditional deployments.
TopIntroduction
As access networks evolve towards Fiber-To-The-Premises (FTTx) network topologies but also cable (considering the increase of up and downward speeds brought by DOCSIS 3.1 (CableLabs, 2014) deployments, and the considerable upstream increase with the current DOCSIS 4.0 specification (currently finished as 2020), to be deployed in the near future (Cablelabs, 2020)). Digital Subscriber Line (DSL) has been progressively phased out, with some providers discontinuing the service for new customers in 2020, while maintaining the service only for existing ones (Brodkin, 2020). This trend spells the end of an era, where the decline of the old copper-based last mile approach with separated vertical service infrastructures gave room to a converged service delivery model, with operators rethinking their service offerings in order to reduce costs and improve manageability, going well beyond the obvious performance benefits of upgrading the physical transport infrastructure.
Despite the evolution of access networks in terms of its role and underlying physical transport technologies, some components of the legacy access network model still persist, maintaining or even increasing their critical role in modern infrastructures. The Residential Gateway (RGW) is one of those components. Considering the present technology developments, the RGW starts to look like an anachronism, as it is a device that mostly embodies the legacy access network model, which remained almost unchanged until today. As such, there is an opportunity to ponder alternative approaches. It is obviously impossible to completely remove the RGW physical device from the customer premises, since it will always be necessary to connect the terminal devices (computers, set-top-boxes, telephones, smartphones, etc.) to the access network. Yet, there is a whole array of RGW features that can be removed from the physical RGW and that can be hosted within the operator’s infrastructure, thanks to advances in virtualization, traffic steering, and access network technologies.
Virtualization technologies have become one of the main driving forces behind the evolution of the Network Service Provider (NSP) infrastructures, also proving instrumental for the introduction of hopefully cost-effective services to end-users, thereby leveraging the return on investment in the infrastructure. This evolution is progressively outgrowing the scope of the data center or the core network, as virtualization reaches towards the edge of the infrastructure and into the access network (Xia, Wu & King, 2013). From this perspective, outsourcing some RGW functionality may appear as a possible application of virtualization techniques potentially contributing to the consolidation and scaling of resources. From this perspective, the vRGW (Virtual RGW) is presented as a logical next step for the evolution of RGW.
Developments in terms of Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) have prompted the industry to start developing standards, specification and companion solutions to incorporate their benefits within NSP infrastructures. Examples such as ETSI’s Open Source MANO (OSM) software stack (which is aligned with ETSI’s NFV standardization effort), have pushed the industry to adopt standard software pieces to implement virtualized RGW functions.
This chapter was originally published in (Cruz et al., 2015), focused on our own proposal for implementing the vRGW. Now, we revise and update it in order to reflect the considerable evolution of the vRGW concept – based upon the development of new standards and virtualization technologies – over the past few years. The chapter is organized as follows: we start by analyzing the rationale for virtualizing some RGW features, the key technologies used for their implementation in particular, such as the infrastructure requirements and coexistence with the legacy RGWs. Next, we present the evolution of vRGW proposals, by detailing current proposals from the academic field, standardization initiatives, and industry. We also identify and discuss the technological enhancements that strengthen the feasibility of the vRGW. Finally, we conclude the chapter by discussing the forthcoming developments of the vRGW.
Key Terms in this Chapter
Broadband Access Networks: Access networks that provide high-speed network connectivity between customers and network service providers.
Network Function Virtualization: In NFV, network node functions, previously carried by dedicated hardware, are virtualized into blocks (Virtual Network Functions or VNFs) that can be chained together to create service abstractions.
Virtualized Residential Gateways (vRGWs): An alternative to conventional, physical gateway appliances, where the physical device is replaced by a simple bridge, with all functionality and services being moved to the operator infrastructure, as a virtualized entity.
Service Delivery: This encompasses the delivery of converged services over IP networks, whether from the operator itself (as it is the case for Triple-Play offers) or from third parties.
Software-Defined Networking: This is a network architecture that decouples the network control and forwarding plane functions, making it possible to introduce flexible and dynamic, flow-oriented network control programmability.
Network Service Provider Infrastructures: It corresponds to the infrastructure elements, such as the networking structure or data centers, that support the operations of organizations that provide network access or converged services.