Internet has truly become the service of the digitized society now and delivers a broad range of services such as banking, eâcommerce, social networking, media, content storage, and much more. Currently, there is a strong trend to penetrate coverage and usage of Internet by going mobile. The usage by individual is steadily increasing both in time of use and bandwidth demand of application in use. Still there is 80% of the global population that lacks access to Internet. Clearly, the technologies building Internet need to evolve in order to facilitate the steady growth by costâefficient and sustainable means. Moreover, it is commonly recognized in the technical literature that the Internet has constraints in terms of mobility, quality of service, security, and scalability (e.g., due to IP address starvation and semantic overloading of IP addresses) even if patches exist for fixing any particular problem.
Over the past decades, the telecommunications industry has migrated from legacy telephony networks to telephony networks based on an IP network. This shift allows the mobile network operators to leverage the high bandwidth, multiplexing, innovative products, and services that have been long deployed and tested in IP network and then stimulates a new wave of revenue generation. Since the emergence of cellular data networks, the volume of data traffic carried by cellular networks has been growing continuously due to the innovation of mobile devices, mobile applications, the rapid increase in subscriber size, and cellular communication bandwidth. The trend of cellular data growth will continue to accelerate as technology and application availabilities further improve. Indeed, in 2009, mobile data traffic exceeded mobile voice traffic for the first time [2, 3], starting the new paradigm of mobile networks. The dominant usage of mobile network has shifted from low bandwidth voice and messaging traffic to a diverse type of data traffic, ranging from web browsing, video streaming, and even online gaming. Existing report [4] has shown that the mobile data traffic is increasing at a rate of 60% per year. By the end of 2016, mobile traffic has surpassed the traffic generated in the wireline network [5, 6]. It is predicted that by the year of 2018, the yearly IP traffic globally will be 64 times of that in 2005.
The demand on mobile network infrastructure will be further increased as the market of Internet of things (IoT) grows. IoT devices and their applications that function without direct human intervention are rapidly becoming an integral part of our lives. IoT devices and applications have wide use cases in a variety of areas, including telehealth, shipping and logistics, utility and environmental monitoring, industrial automation, and asset tracking. It is predicted to be 25 billion devices â including fixed/mobile personal devices and IoT devices â connected to IP networks [5] by the year of 2020 with a seven trillion dollar market value. The MachineâtoâMachine (M2M) communications will generate 80% more data than the human directly generated data in the year of 2018. The prosperity of IoT industry requires great support of the wide area wireless communication infrastructure, in particular, the cellular data networks.
To cope with the explosive cellular data volume growth and best serve their customers, cellular network operators need to design and manage cellular core network architectures accordingly. There are two main challenges that the cellular network faces. The first challenge is the increasing cost of network operation. While the most advanced cellular technologies today is the 4G technology such as long term evolution (LTE). However, the coexistence of multiple generations of cellular networks is unavoidable today. This is because the subscribers may gradually upgrade their devices over the years. Thus, the operators need to support multiple technologies over a long period of time and manage multiple networks simultaneously. The operational cost may not be covered by the revenue growth. The second challenge is the high demand of network capacity expansion. Many techniques have been proposed to expand the cellular network capacity such as multiantenna technologies and WiâFi offloading architecture. Adding spectrum and deploying small/femto cells have also been used together to further expand the network capacity, which is, however, expensive and not easy to deploy. Moreover, the changes of infrastructure still cannot keep up with the exponential growth of traffic demand.
The current cellular infrastructure is not capable of addressing the explosive need of data demand. The main reason is that the resource is configured and allocated in a rather static manner. The resources are not utilized in an efficient way. The traffic demand, however, are highly dynamic, exhibiting a timeâofâday phenomenon [5, 6]. Flash crowds happen often due to popular events. To fundamentally meet the traffic demand, blindly increasing the network capacity is not enough. We need to find ways to better utilize existing capacity.
The traditional business model of cellular carriers was based on revenues for telephony. The Internet was an overâtheâtop service, priced by online minutes or data volumes during the late 1990s. This has changed completely to a flatârateâbased model for Internet access, and operators deploy broadband networks to cover demands of the digital society, struggling to return revenues needed to deploy even higher speed networks. Governance and regulations have further limited profitability of operators. In order to increase revenues, operators are deploying a number of serviceâcentric networks on top of the broadband infrastructure such as IPTV, demanding new functionality of carrier network. On the cost side, carrier operators would like to reduce the capital and operational cost significantly. In the following, we discuss the opportunities of leveraging existing cloud technologies for better resource utilization. We will review the related technologies and then outline the rest of this book.
1.1 CloudâEnabled 5G: SDN and NFV
The Internet has successfully been growing for more than 20 years; the growth in demand has so far been met by introducing even larger and larger routers. This has been beneficial and to scale in public networks. However, in order to meet today's steadily growing demand for Internet access and other packetâbased services, there is a present need to deploy more efficient packet networks also within metro and aggregation network domain. The attempt to copy the approach from the coarsely populated, but large core network sites and migrate to metro and aggregation network sites may not be the most cost optimal approach. It may be time now to split the router architecture in similar ways as was done in the traditional mobile core network, in order to penetrate the highly dense metro/aggregation networks. Splitting the router control and forwarding plane forms the initial idea of softwareâdefined networking (SDN).
The initial idea was born to decouple the routing intelligence software from simple forwarding hardware allowing, particularly for academic research networks and test beds, fast prototyping and evaluation of new control theories and algorithms [7]. It was part of the Clean Slate Internet Design initiative of Stanford University [8]. The target is to develop a system that is amenable to highâperformance and lowâcost implementations and capable of supporting a broad range of research, can isolate experimental traffic from production, and is consistent with vendors' need for closed platforms.
The key technical idea of SDN is to provide an open control interface to the operating system of the network device without compromising the details of the implementation, an important business aspect for equipment manufacturers. This is enabled by support of OpenFlow [8] in the operating system and is based on the Ternary Content Addressable Memory (TCAM)âbased flow tables, most routers and switches make use of. In a classical router or switch, the fast packet forwarding data path and the highâlevel routing decisions in the control path occur on the same device. An OpenFlowâenabled switch separates these two functions. The data path portion still resides in the switch, while highâlevel routing decisions are moved to a flow controller, typically a standard server. The OpenFlow Switch and Controller communicate via the OpenFlow protocol, which defines operation and management (OAM) messages.
Besides this technical view, this split design will enable a cost reduction and new market opportunities by the basic principle of modularization. This is of high importance for supporting flexible network innovations because the development cycles of hardware and software components are extremely different, and the modularization supports a decoupling of the innovations from a market perspective. The right layering approach will enable high market volumes for specific modules (software or hardware).
The introduction of the SDN concept into real networks would have a profound impact on the way in which networks are built and operated. In order to understand and evaluate the practical implications of the general concept, it would be beneficial to first test it in research networks. Feedback from the experimental implementation will be crucial in improving the overall concept and allow taking the concept to further applications in networking. First trials are currently under way in selected US universities, which focus on the easy management and reconfiguration of research networks, for example, for applications in the field of Clean Slate research.
While SDN brings innovative evolution to network routers and switches, the network comprises other types of devices besides routers and switches. Network operators enforce network policies using a combination of switches and network functions (NF). Policies may be complex, such as ensuring that unauthorized users are prevented from accessing sensitive servers or malicious traffic is eliminated from the network. To do this, an operator could use a stateful firewall to ensure that only traffic initiated from within the network is permitted and in doing so protect users from malicious traffic. Indeed, today's networks heavily rely on a wide spectrum of NFs. The diversity and complexity of NFs have been further expanded as the proliferation of wireless devices and mobile applications. NFs offer a variety of valuable benefits, ranging from improving security (e.g., firewalls, intrusion detection systems, and deep packet inspection), improving performance (e.g., proxies, caches) and reducing bandwidth costs (e.g., WAN optimizers, video transcoder). However, despite their benefits, NFs come with high infrastructure and management costs. One important reason is their complex and specialized processing. As a direct result of this complexity, configuration errors are common â configuration e...