Chapter 7: Cloudification of Access¶
The previous chapters went step-by-step, first breaking 5G down into its elemental components and then showing how those components could be put back together using best practices in cloud design to build a fully functional, 3GPP-compliant 5G cellular network. In doing so, it is easy to lose sight of the big picture, which is that the cellular network is undergoing a dramatic transformation. That’s the whole point of 5G. We conclude by making some observations about this big picture.
To understand the impact of cloud technologies and practices being applied to the access network, it is helpful to first understand what’s important about the cloud. The cloud has fundamentally changed the way we compute, and more importantly, the pace of innovation. It has done this through a combination of the following.
Disaggregation: Breaking vertically integrated systems into independent components with open interfaces.
Virtualization: Being able to run multiple independent copies of those components on a common hardware platform.
Commoditization: Being able to elastically scale those virtual components across commodity hardware bricks as workload dictates.
There is an opportunity for the same to happen with the access network, or from another perspective, for the cloud to essentially expand so far as to subsume the access network.
Figure 37 gives a high-level overview of how the transformation might play out, with the global cloud spanning edge clouds, private Telco clouds, and the familiar public clouds. We call this collection of clouds “multi-cloud” (although note that there are a number of other definitions for that term). Each individual cloud site is potentially owned by a different organization (this includes the cell towers, as well), and as a consequence, each site will likely be multi-tenant in that it is able to host (and isolate) applications on behalf of many other people and organizations. Those applications, in turn, will include a combination of the RAN and Core services (as described throughout this book), Over-the-Top (OTT) applications commonly found today in public clouds (but now also distributed across edge clouds), and new Telco-managed applications (also distributed across centralized and edge locations).
Eventually, we can expect common APIs to emerge, lowering the barrier for anyone (not just today’s network operators or cloud providers) to deploy applications across multiple sites by acquiring the storage, compute, networking, and connectivity resources they need.
Of all the potential outcomes discussed in the previous section, one that is rapidly gaining traction is to run a 5G-enabled edge cloud as a centrally managed service. As illustrated in Figure 38, the idea is to deploy an edge cloud in enterprises, configured with the user plane components of the RAN and Mobile Core (along with any edge services the enterprise wants to run locally), and then manage that edge deployment from the central cloud. The central cloud would run a management portal for the edge cloud, along with the control plane of the Mobile Core. This is similar to the multi-cloud configuration discussed in Section 5.2, except with the added feature of being able to manage multiple edge deployments from one central location.
The value of such a deployment is to bring 5G wireless advantages into the enterprise, including support for predictable, low-latency communication required for real-time controlling of large numbers of mobile devices. Factory automation is one compelling use case for such an edge cloud, but interest in supporting IoT in general is giving ECaaS significant momentum.
This momentum has, not surprisingly, led to recent commercial activity. But there is also an open source variant, called Aether, now available for early adopters to evaluate and experiment with. Aether is an ONF-operated ECaaS with 4G/5G support, built from the open source components described throughout this book. Aether works with both licensed and unlicensed frequency bands (e.g., CBRS), but it is the latter that makes it an easy system to opt into. Figure 39 depicts the early stages of Aether’s centrally managed, multi-site deployment.
Note that each edge site in Figure 39 corresponds to a CORD POD described in Chapter 6, re-configured to offload the O&M Interface and the Control elements of the Mobile Core to the central cloud.
For more information about Aether, visit the Aether Web Site. ONF, March 2020.
7.3 Research Opportunities¶
In order for the scenarios described in this Chapter to become a reality, a wealth of research problems need to be addressed, many of which are a consequence of the blurring line between access networks and the edge cloud. We refer to this as the access-edge, and we conclude by identifying some example challenges/opportunities.
Multi-Access: The access-edge will need to support multiple access technologies (e.g., WiFi, 5G, fiber), and allow users to seamlessly move between them. Research is needed to break down existing technology silos, and design converged solutions to common problems (e.g., security, mobility, QoS).
Heterogeneity: Since the access-edge will be about low-latency and high-bandwidth connectivity, much edge functionality will be implemented by programming the forwarding pipeline in white-box switches, and more generally, will use other domain-specific processors (e.g., GPUs, TPUs). Research is needed to tailor edge services to take advantage of heterogeneous resources, as well as how to construct end-to-end applications from such a collection of building blocks.
Virtualization: The access-edge will virtualize the underlying hardware using a range of techniques, from VMs to containers to serverless functions, interconnected by a range of L2, L3, and L4/7 virtual networks, some of which will be managed by SDN control applications. Research is needed to reconcile the assumptions made about by cloud native services and access-oriented Virtualized Network Functions (VNFs) about how to virtualize compute, storage, and networking resources.
Multi-Tenancy: The access-edge will be multi-tenant, with potentially different stakeholders (operators, service providers, application developers, enterprises) responsible for managing different components. It will not be feasible to run the entire access-edge in a single trust domain, as different components will operate with different levels of autonomy. Research is needed to minimize the overhead isolation imposes on tenants.
Customization: Monetizing the access-edge will require the ability to offer differentiated and customized services to different classes of subscribers/applications. Sometimes called network slicing (see Section 5.3), this involves support for performance isolation at the granularity of service chains—the sequence of functional elements running on behalf of some subscriber. Research is needed to enforce performance isolation in support of service guarantees.
Near-Real Time: The access-edge will be a highly dynamic environment, with functionality constantly adapting in response to mobility, workload, and application requirements. Supporting such an environment requires tight control loops, with control software running at the edge. Research is needed to analyze control loops, define analytic-based controllers, and design dynamically adaptable mechanisms.
Data Reduction: The access-edge will connect an increasing number of devices (not just humans and their handsets), all of which are capable of generating data. Supporting data reduction will be critical, which implies the need for substantial compute capacity (likely including domain-specific processors) to be available in the access-edge. Research is needed to refactor applications into their edge-reduction/backend-analysis subcomponents.
Distributed Services: Services will become inherently distributed, with some aspects running at the access-edge, some aspects running in the datacenter, and some running on-premises or in an end device (e.g., on-vehicle). Supporting such an environment requires a multi-cloud solution that is decoupled from any single infrastructure-based platform, with research needed to develop heuristics for function placement.
Scalability: The access-edge will potentially span thousands or even tens of thousands of edge sites. Scaling up the ability to remotely orchestrate that many edge sites (even at just the infrastructure level) will be a qualitatively different challenge than managing a single datacenter. Research is needed to scale both the edge platform and widely deployed edge services.
To better understand the research opportunity at the access-edge, see Democratizing the Network Edge. ACM SIGCOMM CCR, April 2019.