Contributed by Dell Technologies.
Where is the Network Edge in Mobile Networks
The notion of ‘Edge’ can take on different meanings depending on the context, so it’s important to first define what we mean by Network Edge. This term can be broadly classified into two categories: Enterprise Edge and Network Edge. The former refers to when the infrastructure is hosted by the company using the service, while the latter refers to when the infrastructure is hosted by the Mobile Network Operator (MNO) providing the service.
This article focuses on the Network Edge, which can be located anywhere from the Radio Access Network (RAN) to next to the Core Network (CN). Network Edge sites collocated with the RAN are often referred to as Far Edge.
What is in the Network Edge
In a 5G Standalone (5G SA) Network, a Network Edge site typically contains a cloud platform that hosts a User Plane Function (UPF) to enable local breakout (LBO). It may include a suite of consumer and enterprise applications, for example, those that require lower latency or more privacy. It can also benefit the transport network when large content such as Video-on-Demand is brought closer to the end users.
Modern cloud platforms are envisioned to be open and disaggregated to enable MNOs to rapidly onboard new applications from different Independent Software Vendors (ISV) thus accelerating technology adoption. These modern cloud platforms are typically composed of Commercial-of-the-Shelf (COTS) hardware, multi-tenant Container-as-a-Service (CaaS) platforms, and multi-cloud Management and Orchestration solutions.
Similarly, modern applications are designed to be cloud-native to maximize service agility. By having microservices architectures and supporting containerized deployments, MNOs can rapidly adapt their services to meet changing market demands.
What contributes to Network Latency
The appeal of Network Edge or Multi-access Edge Computing (MEC) is commonly associated with lower latency or more privacy. While moving applications from beyond the CN to near the RAN does eliminate up to tens of milliseconds of delay, it is also important to understand that there are many other contributors to network latency which can be optimized. In fact, latency is added at every stage from the User Equipment (UE) to the application and back.
RAN is typically the biggest contributor to network latency and jitter, the latter being a measure of fluctuations in delay. Accordingly, 3GPP has introduced a lot of enhancements in 5G New Radio (5G NR) to reduce latency and jitter in the air interface. We can actively reduce latency through the following categories: There are three primary categories where latency can be reduced:
- Transmission time: reduce symbol duration with higher subcarrier spacing or with mini slots
- Waiting time: improve scheduling (optimize handshaking), simultaneous transmit/receive, and uplink/downlink switching with TDD
- Processing time: reduce UE and gNB processing and queuing with enhanced coding and modulation
Transport latency is relatively simple to understand as it is mainly due to light propagation in optical fiber. The industry rule of thumb is 1 millisecond round trip latency for every 100 kilometers. The number of hops along the path also impacts latency as every transport equipment adds a bit of delay.
Typically, CN adds less than 1 millisecond to the latency. The challenge for the CN is more about keeping the latency low for mobile UEs, by seamlessly changing anchors to the nearest Edge UPF through a new procedure called ‘make before break’. Also, the UPF architecture and Gi/SGi services (e.g., Deep Packet Inspection, Network Address Translation, and Content Optimization) may add a few additional milliseconds to the overall latency, depending on whether these functions are integrated or independent.
Architectural and Business approaches for the Network Edge
The physical locations that host RAN and Network Edge functionalities are widely recognized to be some of the MNOs’ most valuable assets. Few other entities today have the real estate and associated infrastructure (e.g., power, fiber) to bring cloud capabilities this close to the end clients. Consequently, monetization of the Network Edge is an important component of most MNOs’ strategy for maximizing their investment in the mobile network and, specifically, in 5G. In almost all cases, the Network Edge monetization strategy includes making Network Edge available for Enterprise customers to use as an “Edge Cloud.” However, doing so involves making architectural and business model choices across several dimensions:
- Connectivity or Cloud: should the MNO offer a cloud service or just the connectivity to a cloud service provided by a third party (and potentially hosted at a third party’s site).
- aaS model: in principle, the full range of as-a-Service models are available to the MNO to offer at the network edge. This includes co-location services; Bare-Metal-as-a-Service, Infrastructure-as-a-Service (IaaS), Containers-as-a-Service (CaaS), and Platform and Software-as-a-Service (PaaS and SaaS). Going up this value chain (up being from co-lo to SaaS) allows the MNO to capture more of the value provided to the Enterprise. However, it also requires it to take on significantly more of responsibility and puts it in direct competition with well-established players in this space – e.g., the cloud hyperscale companies. The right mix of offerings – and it is invariably a mix – thus involves a complex set of technical and business case tradeoffs. The end result will be different for every MNO and how each arrives there will also be unique.
- Management framework: our industry’s initial approach to exposing the Network Edge to the enterprises involved a management framework that tightly couples to how the MNO manages its network functions (e.g., the ETSI MEC family of standards for example (ETSI MEC)). However, this approach comes with several drawbacks from an Enterprise point of view. As a result, a loosely coupled approach, where the Enterprise manages its Edge Cloud applications using typical cloud management solutions appears to be gaining significant traction, with solutions such as Amazon’s Wavelength as an example. This approach, of course, has its own drawbacks and managing the interplay between the two is an important consideration in Network Edge (and one that is intertwined with the selection of aaS model).
- Network-as-a-Service: a unique aspect of the Network Edge is the MNOs ability to expose network information to applications as well as the ability to provide those applications (highly curated) means of controlling the network. How and if this makes sense is again both an issue of the business case – for the MNO and the Enterprise – as well as a technical/architectural issue.
Certainly, the likely end state is a complex mixture of services and go-to-market models focused on the Enterprise (B2B) segment. The exposition of operational automation and the features of 5G designed to address this make it likely that this is a huge opportunity for MNOs. Navigating the complexities of this space requires a deep understanding of both what services the Enterprises are looking for and how they are looking to consume these. It also requires an architectural approach that can handle the variable mix of what is needed in a way that is highly scalable.
As the long-time leader in Enterprise IT services, Dell is uniquely positioned to address this space – stay tuned for more details in an upcoming blog!
Building the Network Edge
There are several factors to consider when moving workloads from central sites to edge locations. Limited space and power are at the top of the list. The distance of locations from the main cities and generally more exposed to the elements require a new class of denser, easier-to-service, and even ruggedized form factors. Thanks to the popularity of Open RAN and Enterprise Edge, there are already solutions in the market today that can also be used for Network Edge. Read more on Edge blog series Computing on the Edge | Dell Technologies Info Hub
Higher deployment and operating costs are another major factor. The sheer number of edge locations combined with their degraded accessibility make them more expensive to build and maintain. The economics of the Network Edge thus necessitates automation and pre-integration. Dell’s solution is the newly engineered cloud-native solution with automated deployment and life-cycle management at its core. More on this novel approach here Dell Telecom MultiCloud Foundation | Dell USA.
Last is the lower cost of running applications centrally. Central sites have the advantage of pooling computes and sharing facilities such as power, connectivity, and cooling. It is therefore important to reduce overhead wherever possible, such as opting for containerized over VM-based cloud platforms. Moreover, having an open and disaggregated horizontal cloud platform not only allows for multitenancy at edge locations, which significantly reduces overhead but also enables application portability across the network to maximize efficiency.
The ideal situation is where Open/Cloud RAN and Network Edge are sharing sites thus splitting several of the deployment and operations costs. Due to the latency requirements, Distributed Unit (DU) must be placed within 20 kilometers of the Radio Unit (RU). Latency requirements for the mid-haul interface between DU and Central Unit (CU) are less stringent, and CU could be placed roughly around 80-100 kilometers from the DU. In addition, the Near-Real Time Radio Intelligent Controller (Near-RT RIC) and the related xApps must be placed within 10ms RTT. This makes it possible to collocate Network Edge sites with the CU sites and Near-RT RIC.
What has happened over the past few years is that several MNOs have already moved away from having 2-3 national DCs for their entire CN to deploying 5-10 regional DCs where some network functions such as the UPF were distributed. One example of this is AT&Ts dozen “5G Edge Zones” which were introduced in the major metropolitan areas: AT&T Launching a Dozen 5G “Edge Zones” Across the U.S. (att.com).
This approach already suffices for the majority of “low latency” use cases and for smaller countries even the traditional 2-3 national DCs can offer sufficiently low transport latency. However, when moving into critical use cases with more stringent latency requirements, which means consistently very low latency is a must, then moving the applications to the Far Edge sites becomes a necessity in tandem with 5G SA enhancements such as network slicing and an optimized air interface.
The challenge with consumer use cases such as cloud gaming is supporting the required Service Level (i.e., low latency) country wide. And since enabling the network to support this requires a substantial initial investment, we are seeing the classic chicken and egg problem where independent software vendors opt not to develop these more demanding applications while MNOs keep waiting for these “killer use cases” to justify the initial investment for the Network Edge. As a result, we expect geographically limited enterprise use cases to gain market traction first and serve as catalysts for initially limited Network Edge deployments.
For use cases where assured speeds and low latency are critical, end-to-end Network Slicing is essential. In order to adopt a new more service-oriented approach, MNOs will need Network Edge and low latency enhancements together with Network Slicing in their toolbox. For more on this approach and Network Slicing, please check out our previous blog To slice or not to slice | Dell Technologies Info Hub.
About the author: Tomi Varonen
Tomi Varonen is a Telecom Network Architect in Dell’s Telecom Systems Business Unit. He is based in Finland and working with the Cloud, Core Network, and OSS&BSS customer cases in the EMEA region. Tomi has over 23 years of experience in the Telecom sector in various technical and sales positions. Wide expertise in end-to-end mobile networks and enjoys creating solutions for new technology areas. Passion for various outdoor activities with family and friends including skiing, golf, and bicycling.
About the author: Arthur Gerona
Arthur is a Principal Global Enterprise Architect at Dell Technologies. He is working on the Telecom Cloud and Core area for the Asia Pacific and Japan region. He has 19 years of experience in Telecommunications, holding various roles in delivery, technical sales, product management, and field CTO. When not working, Arthur likes to keep active and travel with his family.
About the author: Alex Reznik
ALEX REZNIK is a Global Principal Architect in Dell Technologies Telco Solutions Business organization. In this role, he is focused on helping Dell’s Telco and Enterprise partners navigate the complexities of Edge Cloud strategy and turning the potential of 5G Edge transformation into the reality of business outcomes. Alex is a recognized industry expert in the area of edge computing and a frequent speaker on the subject. He is a co-author of the book “Multi-Access Edge Computing in Action.” From March 2017 through February 2021, Alex served as Chair of ETSI’s Multi-Access Edge Computing (MEC) ISG – the leading international standards group focused on enabling edge computing in access networks.
Prior to joining Dell, Alex was a Distinguished Technologist in HPE’s North American Telco organization. In this role, he was involved in various aspects of helping Tier 1 CSPs deploy state-of-the-art flexible infrastructure capable of delivering on the full promises of 5G. Prior to HPE Alex was a Senior Principal Engineer/Senior Director at InterDigital, leading the company’s research and development activities in the area of wireless internet evolution. Since joining InterDigital in 1999, he has been involved in a wide range of projects, including leadership of 3G modem ASIC architecture, design of advanced wireless security systems, coordination of standards strategy in the cognitive networks space, development of advanced IP mobility and heterogeneous access technologies and development of new content management techniques for the mobile edge.
Alex earned his B.S.E.E. Summa Cum Laude from The Cooper Union, S.M. in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology, and Ph.D. in Electrical Engineering from Princeton University. He held a visiting faculty appointment at WINLAB, Rutgers University, where he collaborated on research in cognitive radio, wireless security, and future mobile Internet. He served as the Vice-Chair of the Services Working Group at the Small Cells Forum. Alex is an inventor of over 160 granted U.S. patents and has been awarded numerous awards for Innovation at InterDigital.