What role do SDN and NFV play on the 5G network?
As I started to understand the 5G core network architecture, I noticed that the Software Definition Network (SDN) and Network Function Virtualization (NFV) was mentioned twice as two emerging technologies. However, many articles ignore the important role played by SDN and NFV technology in 5G, and many technical blogs are also from a professional operator’s point of view to emphasize the time and cost savings brought about by the introduction of SDN and NFV to operators, which actually makes me very confused, Because I still do not understand why SDN and NFV technology can have such a great potential to fundamentally understand the importance of these two technologies for 5G. As beginners, it is difficult to fully understand the entire 5G core network technology system if it is not understood in its essence. So I do some inductive finishing here, hope to help beginners.
What role do SDN and NFV play on the 5G network?
Why introduce SND technology and NFV technology for 5G?
This begins with a major flaw in the current core network EPC, a flaw that is coupled! At the beginning of the construction, EPC did not consider the problem from the point of view of service and infrastructure. Instead, a centralized architecture designed for a single service (use scenario) results in a very coupling of functional partitioning between physical components in the EPC architecture, coupled with the difficulty of deployment, and the realization of the functionality relies heavily on physical hardware, The implementation of many features must be based on expensive proprietary devices.

In conclusion, the coupling of the traditional EPC network is mainly embodied in two aspects:

Control plane and user plane coupling;
Hardware and software coupling.
The coupling of these two areas brings three limitations:

Such a traditional architecture creates cost and time challenges for operators to deploy their networks;
As terminal types and numbers and service types become more and more, it is difficult to develop new features and services for this “behemoth” and to allocate resources efficiently;
Reduce user QoS experience (QoS).
We will further explain the above-mentioned “coupling” problem with the next EPC network architecture diagram. Such as Figure 1, EPC has four components:

MME: mobile management entity, responsible for the management of network connectivity, including the user terminal authentication and authorization, session establishment and mobility management;
HSS: home user server, as the user data set for the MME to provide user-related data, in order to assist the management of MME;
SGW: The service gateway, responsible for packet routing and forwarding, forwards the received user data to the specified PGW, and delivers the returned data to the eNB;
PGW: PDN gateway, responsible for the allocation of IP addresses for users and the user plane QoS management, and is the PND network entry point.
From the dashed and solid lines in Figure 1, it can be seen that the MME only assumes the control plane function, but the SGW and PGW assume both the user plane function and the part of the control plane function, which makes the user plane and the control plane seriously, Thus limiting the openness and flexibility of EPC. On the other hand, in this architecture, many network elements must run on a number of blade servers with dedicated hardware, which is a great expense for operators.

What are the basic concepts of SDN technology and NFV?
SDN Technology is a new kind of network architecture which separates the control plane of network equipment from the forwarding plane and realizes the software programmable in the centralized control plane. We know that in the traditional network, the control plane function is distributed in each network node (such as hubs, switches, routers, etc.), so if you want to deploy a new network function, you must upgrade all network equipment, which greatly limits the network innovation! From this point of view, SDN is the emergence of the “Savior”! SDN adopts centralized control plane and distributed forwarding plane, two planes are separated from each other, the control plane utilizes the control-forwarding communication interface to centralize the control over the network devices on the forwarding plane, and provides flexible programmable capability upward. Because of this “talent”, the Sdn naturally becomes the “nemesis” of the interface of the EPC control surface and the user interface.

NFV technology is a technology that integrates network functionality into industry-standard servers, switches, and storage hardware, and provides an optimized virtualized data plane that allows administrators to replace traditional physical network devices with software running on the server. Since ancient times have such a truth: the dependence on the external physical entities stronger, the more detrimental to their own development. Independence, in my opinion, is a significant good quality, which is also reflected in the network technology. Dependence on dedicated network equipment will lead us in the face of network innovation when the powerless, which at this stage of the EPC has been confirmed, so we must seek new technology to get rid of the dependence on dedicated hardware! By using NFV, you can reduce or even remove middleware deployed in existing networks, enabling a single physical platform to run on different applications where users and tenants can use the network capabilities through multiple versions and multi-tenants to facilitate the software network environment In the new network features and service innovations, NFV is suitable for any data plane and control plane functions, fixed or mobile networks, and is also suitable for the need for scalability to automate management and configuration.

The SDN and NFV can be summarized as follows: SDN technology is a solution to the problem of EPC control plane and user plane coupling. Decoupling user plane and control plane can make the deployment of user plane function more flexible, The user plane functionality can be deployed closer to the user’s wireless access network, thereby improving the user service quality experience, such as reducing latency. NFV technology is a solution to the serious coupling of EPC software and hardware, which allows operators to deploy network functions on common servers, switches and storage devices, greatly reducing time and cost.

SDN and NFV Technologies have spawned a 5G core network architecture, as shown in Figure 2:

5G Core Network Architecture

On this basis, some literatures propose that 5G architecture should reduce the network entity as far as possible, and cancel the concept of service gateway and PDN Gateway, and abstract it into the control plane gateway and user plane Gateway, and propose that the control planar gateway and the user plane gateway run in the operator’s cloud system in the form of software, Rather than using a dedicated hardware device. The proposed architecture is shown in Figure 3:

NextGen Cord Network

In short, regardless of what the future 5G core network architecture, SDN technology, and NFV technology combination, will make the 5G core network in the high efficiency, programmability, and flexibility on the qualitative leap! It is a huge gospel for the operators to deploy the network and users to enjoy better service.
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