Present-day carrier network operators are faced with the challenge of
supporting unprecedented growth in services and subscriber base
while keeping the capital and operational expenditures low. Carriers are
integrating datacenters into networks to deploy innovative services. This
paper discusses application of software-defined networking (SDN) and
Network Function Virtualization (NFV) technologies to the emerging
unified datacenter-network model to address this challenge.
Introduction
The ongoing convergence of video, cloud-based applications, and the exploding adoption of mobile devices and services are having an unprecedented impact on carrier networks. Network operators are under tremendous pressure to deploy newer, value-added services to increase revenue per user and grow subscriber numbers while lowering capital expenditure (CapEx) and operational expenditures (OpEx). In order to meet this challenge, carriers leverage datacenters to help create these services and results in tighter integration of the traditionally separate datacom/IT and telecom networks to form a unified network. Now, by extending the virtualization technologies that are already well-adopted in datacenters into the carrier network domain, the overall end-to-end network utilization and operational efficiencies can be improved and become more cost effective. This white paper discusses the application of the popular virtualization techniques– software-defined networking (SDN) and network function virtualization (NFV) – to the carrier network infrastructure.
Drivers for virtualization of carrier networks in a unified datacenter-carrier network
In recent years, consumer expectation to access business and entertainment applications and services “anywhere, any time” is changing the service model provided by carrier network operators. E-commerce is adopting cloud technologies rapidly, and service providers need to incorporate business applications in their service model. On the entertainment side, the video streaming content includes not only the traditional movies, but also user-created content and Internet video; while the video delivery mechanism is evolving as well to include streaming onto a variety of fixed and mobile platforms. Present-day powerful and feature-rich mobile devices serve as e-commerce and entertainment platforms in addition to their traditional role as communication devices, fueling deployment of new applications such as mobile TV, online gaming, Web 2.0 and personalized video. Figure 1 shows the trend in worldwide telecom
Software-defined networking and
Network Function Virtualization-based
approach for optimizing a carrier
growth, according to an Insight research report. It states that the telecom services revenue is expected to reach $2.1 trillion in 2017. In addition to services, there has been a dramatic increase in the number of subscribers. According to Infonetics research, the number of mobile broadband subscribers is expected to reach 2.6 billion by 2016, as indicated in Figure 2.
Global carrier revenue by region, 2012-2017. (PRNewsFoto/Global Information, Inc.)
$Billions $1,200 $1,000 $800 $600 $400 $200 $0 NA EMEA AP LAC 2012 2013 2014 2015 2016 2017
Source: Insight research
http://www.prnewswire.com/news-releases/worldwide-telecom-industry-revenue-to-reach-27-trillion-by-2017-says-insight-research-corp-137423078.html
Mobile subscribers are forecast
to total ~ 7 billion worldwide by 2016
M obile subscr ibers in billions 8 4 0 2012 2313 2014 2015 2016
© Infonetics Research. Total Fixed and Mobile Subscribers Pivot Annual market Size and Forecast. April2012
Source: Infonetics research: http://www.infonetics.com/pr/2012/Fixed-and-Mobile-Subscribers-Market-Highlights.asp
It is critical for carriers to offer value-added services to increase the average revenue per user (ARPU); however, to achieve these cost-effectively they have to leverage datacenters which help create these new services. Therefore, datacenters that help create these new services are becoming as critical as the networks themselves when it comes to providing services to subscribers.
Datacenters and carrier networks are very dissimilar in their architectures and operational models, which makes unifying them for a seamless end-to-end connection complex and costly. According to The Yankee Group, about 30% of the total OpEx of a service provider is due to networks costs (as shown in Figure 3). Service providers are being pushed to find solutions that enable them to seamlessly leverage an integrated datacenter model to optimize their network for better utilization while reducing overall CapEx and OpEx. Virtualization of a network infrastructure is one strategy to achieve this cost-effectively. It has been a well-proven strategy that has been universally adopted by the enterprise IT industry for improving utilization and operational efficiency of datacenter server, storage and network resources. By extending the virtualization principles into the various segments of a carrier network, end-to-end virtualization can be achieved for the unified datacenter-carrier networks, making them scalable and adaptable.
Network Costs represent
significant part of operators
expenditures
Marketing Sales & Admin
Cost of Goods Sold (Interconnect)
Network Costs
Customer Care
Source: Yankee Group
30 %
Figure 3: Chart showing mobile network costs
Benefits of integrating datacenters into a carrier network
Leveraging the integrated datacenter model and virtualization into a carrier network has several benefits that can help address the growing subscriber base and performance expectations while reducing CapEx and OpEx. Carriers can seamlessly launch new services for business and consumers such as Software-as-a-Service (SaaS) or video acceleration. Google, Facebook and Amazon are some examples that require an integrated datacenter model to process, store and transport massive data (Big Data). They are able to leverage datacenter virtualization architectures, such as multi-tenant compute or content delivery networks, to scale or deploy new services without investing in expensive hardware upgrades. Incorporating
the datacenter model can also allow carriers to centralize their billing support system (BSS) and operation support system (OSS) stacks, doing away with their distributed, heterogeneous network elements and consolidating them to centralized servers. Furthermore, by using commodity servers instead of proprietary network elements, carriers are able to improve CapEx and OpEx while reducing management complexity.
Integrated datacenter-carrier virtualization technology trends
Virtualization of server, storage and network resources in datacenters is mature and well established as mentioned earlier. The physical resources are masked using virtualization software called hypervisors, which create and manage virtual machines (VMs) on which applications are executed.
While the telecom industry has lagged behind the IT industry in fully implementing virtualization techniques, at present service providers are actively working on adapting virtualization principles into carrier networks. The NFV is one such concept, which is being developed by the collaboration of several service providers. NFV can be used for decoupling and virtualizing carrier network functions from traditional network elements and distributing them across the network for cost reductions. A carrier network made up of a heterogeneous hardware platform can significantly benefit from NFV technology, as network functions can be consolidated to run on VMs executed on common hardware platforms. The NFV concept is described in the next section.
Another trend in present-day virtualized datacenters is network abstraction using SDN. SDN allows datacenter networks to become more manageable and open for innovations. It is shifting the network paradigm by abstracting and presenting a logical view of the network by decoupling it from the physical topology. SDN technology is highly applicable to carrier networks, which are made up of disparate network segments based on heterogeneous hardware platforms.
Technical overview of SDN and NFV
With the increasing adoption of NFV and SDN by carriers, let us look more closely at these technologies and their benefits, and provide practical applications in an integrated datacenter-carrier network.
SDN
SDN is a network virtualization technique based on the logical separation and abstraction of both control and data plane functions, as shown in Figure 4. Using SDN, the network elements, such as switches, routers, etc., can be implemented in software, virtualized as shown and executed anywhere in a network, including the cloud. SDN decouples the network functions from the underlying physical resources using OpenFlow®, the standard vendor-agnostic interface developed by the Open Networking Foundation (ONF), enabling hardware manufactured by multiple vendors to work together. With SDN, a network administrator can deploy a new network application by writing a simple software program that manipulates the logical map for a slice of the network.
SDN is highly applicable to carrier networks since they are typically composed of
heterogeneous hardware platforms and protocols, and offers several benefits to the unified carrier-datacenter network. It opens up the network for incorporating innovations, and network administrators can add utilities to manage and control networks easily. It allows carriers and datacenters to reduce CapEx by using commodity servers and services, as well as the ability to mix and match platforms from different vendors. For example, in a datacenter, network functions can be decoupled from network elements, like line and control cards, and moved onto commodity servers. These commodity servers provide mature virtualization technologies on industry-standard processors and software solutions versus using proprietary network infrastructure. SDN also enables higher security as the OpenFlow architecture requires authentication while establishing a connection between end-stations. Since a mobile carrier network has to support a variety of secure and non-secure applications, third-party and user-defined APIs, security is a significant challenge. Carriers can leverage SDN’s authentication feature to augment their security functions.
CONTROL PLANE
DATA PLANE
LOGICAL MAP OF NETWORK
ROUTING TE MOBILITY NETWORK OS PACKET FORWARDING PACKET FORWARDING PACKET FORWARDING PACKET FORWARDING
Figure 4: Diagram showing SDN concept
Source: Open Networking Foundation
NFV
NFV is an initiative driven by network operators to apply virtualization to telecom in an effort to lower end-to-end network expenditures. Using NFV, many network equipment types can be consolidated into industry-standard volume servers, switches and storage to increase efficiency and lower costs. It decouples network functions from traditional network elements, like switches, routers and appliances, enabling these task-based functions to then be centralized or distributed across network elements. Figure 5 illustrates a virtualized carrier network in which network functions such as a mobility management entity (MME) are run on VMs based on a common hardware platform and an Open Source hypervisor such as a KVM. Similar to SDN, this enables multi-vendor hardware consolidation and use of commodity servers.
NFV and SDN are complementary technologies that can be applied independent of each other. NFV provides the infrastructure upon which SDN software can run. Using NFV combined with the SDN concept of separating the control and dataplanes, network performance can be enhanced, management can be simplified and innovations can be seamlessly deployed.
Co m m on ce nt ra liz ed co nt ro l pla tfo rm ag en t VM VM VM SGW OS PGW OS MME OS KVM KVM KVM
Applications control plane
package process
multicore hardware Applications user plane
packet process multicore hardware N et w or k i nt er fa ce a nd sw itc h m ult ico re h ar dw ar e Sy ste m co nt ro lle r an d m an ag er m ult ico re h ar dw ar e Co m m on ha rd w ar e p la tfo rm C O N N EC T I V A
Figure 5: Conceptual view of a carrier network infrastructure showing virtualization of network functions
Application of SDN and NFV to integrated datacenter-carrier network
Carriers are connection-oriented while datacenters are based on connectionless protocols such as Ethernet. In order for carriers to fully integrate a datacenter, a common set of protocols and techniques is needed. For example, protocols such as VxLAN and NvGRE, which allow support for thousands of VMs in a datacenter, can be extended for carriers and provide scalability. Connection-oriented tunneling protocols such as IPSec can be used to establish virtual private networks (VPN) for end-to-end network connection.
In addition to these well-known protocol-level techniques, the network-abstraction technique based on SDN can enable the merging of datacenters into carrier networks. We will now discuss how the concepts of SDN, mentioned earlier, can be applied to various segments of a carrier network and how the functions of a traditional carrier network can be offloaded to a virtualized datacenter to improve end-to-end performance.
Offloading of network control functions to a virtualized datacenter using SDN
As mentioned earlier, using the SDN concept, the control plane components, like discovery, dissemination of network state, etc., can be decoupled and executed on a centralized datacenter using commodity servers instead of diverse and distributed network elements. A centralized control plane has the advantage of an end-to-end network state view and enables the network operator to allocate hardware resource pools based on the application needs. It allows the network operator to use standard APIs to monitor and manage the network with end-to-end visibility, and enable them to provision the network according to the number of active subscribers, local network, etc.
Offloading of network application software to a virtualized datacenter using SDN
SDN enables a centralized control platform that manages hardware resources and allows core applications to be virtualized and executed on datacenters. In case of a “software-on-demand” situation, based on the requirements of the services, a network operator can program a core application software to run on the hardware platform in a geographical location with required processing capacity. For example, in order to provide LTE services in a given city, one operator might program S-GW, P-GW and MME software to run on a platform with the required processing capacity located in that city, but because the network is abstracted using SDN, the operator need not manage the underlying hardware.
Application of SDN and NFV to carrier network segments
The carrier network is composed of access networks that connect the subscriber devices to service providers, transport network and core networks, which interconnect service providers as shown in Figure 6.
Access
Mobile Backhaul Gateways 2.5G 3G 4G eNodeB NodeB BTS SGW MGW SGSN RNC BSC GGSN Network Network Microwave,Copper,Fiber Core TDM/ATM IP Network IP Network TDM/ATM
Applying virtualization schemes based on NFV and SDN allows the entire network to run on a common, generic and multi-purpose hardware resource pool. This reduces network complexity significantly and simplifies network management. By leveraging centralized control and virtualized hardware platforms, core applications share a common hardware pool to provide scalability and resource optimization. New services and upgrades can be achieved through software instead of the costly hardware upgrades.
Figure 7 below shows a conceptual view of the SDN-based carrier network. The hardware platform is decoupled and the disparate cellular technologies run on the virtualized network elements and are agnostic to the hardware infrastructure. In sections below, we will discuss how NFV and SDN can optimize different segments of carrier networks.
Common hardware platform Common network element functionality 2G SGSN 3G SGSN LTE MME
Software independent from hardware Common software platform
Figure 7: Conceptual view of SDN-based carrier network
Application of SDN and NFV for core networks
Carrier mobile core networks consist of network elements that reside between radio access networks (RANs) and the Internet, as shown above in Figure 6, and they are adopting packet-based switching from the traditional model of cell and packet switching. Core networks are transforming to support towards a variety of cellular technologies such as 3G, long-term evolution (LTE), 4G, etc. The underlying core network functions, such as packet forwarding, and control tasks like mobility management, session handling, security and charging are implemented through dedicated network elements. For example, a serving gateway (SGW) routes and forwards packets, and an MME is responsible for activation or authentication in an LTE network. They are executed typically on proprietary common hardware platforms, which are closed systems. In addition, applications become visible to one another resulting in management, resource sharing and security problems. Using the SDN concept, these issues can be mitigated as well as support newer technologies and use cases. An example solution is shown in Figure 8. In this example, dedicated application software, which implements network functions for each dedicated core network element, such as gateway support nodes
MME SGSN MME SGSN GGSN S/P GW S/P GW GGSN
Core software in the cloud environment
Common centralized control platform
Common Hardware Pool
Commercial Hardware Commercial Hardware Commercial Hardware Commercial Hardware
Figure 8: SDN application in core network
Application of SDN and NFV for carrier access networks
The access network connects the end-point subscriber devices to a service provider. The access network, which provides wireless connectivity between mobile devices and the core network through a radio control, is referred to as a RAN, as shown in Figure 6. A RAN consists of a base station unit, which implements the radio access. Because of the exploding mobile device adoption and mobile data usage worldwide, RAN has to be optimized. The main challenges encountered for a RAN are:
■ rapidly increasing number of base stations needed to cover a given area with LTE eNB deployments
■ low base station utilization ■ high power consumption
■ low utilization of RF bandwidth resulting from RF interference and limited network capacity and
■ multi-standard environment.
Virtualization of resources in a base station based on SDN and NFV is a critical technique for addressing these challenges. Base station virtualization is enabled by the real-time virtualized operating system running on top of a base station unit pool, as indicated in Figure 9. It manages and allocates all the physical layer processing resources in a given centralized baseband pool. The virtualized operating system dynamically allocates the processing resources based on each virtualized base station’s requirements in order to meet its demands dynamically by software. The base station instances of different standards for different application software running on top of the real-time virtualized OS can be easily built up through resource reconfigurations in software.
By applying the SDN architecture, baseband pools with high-bandwidth, low-latency interconnects can be centralized to form “baseband clouds.” A centralized control plane, which has the global view of all physical processing resources in the cloud, enables network operators to program baseband processing tasks for different standards. For instance, operators can deploy 3G RAN or 4G RAN by programming different virtual base stations respectively through software and adjust capacity of existing RAN through software reconfigurations.
Physical hardware Basestation virtualization Basestation instances
PHY layer (signal processing) resource pool MAC/Trans.layer (packet processing) resource pool Accelerator (CODEC, cryto, etc.)
resource pool
Control & manage (O&M processing) resource pool A C M P BS of standard 1 A C M P BS of standard 2 A C M P BS of standard 3 Processors Processors Processors Processors
Figure 9: Example of a virtualized base station
Finally, Figure 10 shows an implementation of a “cloud-based RAN (C-RAN)” architecture, proposed by China Mobile - CMCC. The wireless remote radio heads connect to a cloud-based, virtualized base station cluster, which can be implemented using SDN running on heterogeneous hardware processors.
RRH RRH RRH RRH RRH RRH RRH Virtual BS pool
L1/L2/L3/O&M L1/L2/L3/O&M L1/L2/L3/O&M
Fiber RRH/L1 RRH/L1 RRH/L1 RRH/L1 RRH/L1 RRH/L1 RRH/L1 Virtual BS pool
L2/L3/O&M L2/L3/O&M L2/L3/O&M
Fiber or microwave
Figure 10: Example of a cloud RAN (C-RAN) architecture
Application of SDN and NFV for carrier transport networks
The transport network in wireless infrastructure includes the backhaul network connecting the base stations, terminates at the core network (as shown in Figure 6) and implements many technologies including SONET/PDH, TDM/PDH, carrier Ethernet and IP packet transport network. Each protocol has distinct characteristics. For example, the TDM operational model is a simple model characterized by static routes and traffic flows across the network’s centralized control. In contrast, today’s IP network operational model supports dynamic routing of traffic across the network and implements distributed network control. SDN combines these two technologies to leverage their strengths, i.e., the simplicity of static network routing can be combined with the flexibility and economic advantages of the IP transport model. Using SDN, network control is decoupled from traffic-forwarding function, virtualized and centralized to run on a network control plane. The distributed transport network element provides static routes and traffic flows across the network. SDN along with OpenFlow provides operators with the ability to program their networks in software.
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The telecom industry today, fueled by exploding growth in mobile data usage and
subscriber base, is undergoing a huge transformation. Service providers are under enormous pressure to deploy newer value-added services at lower costs. To achieve this, carriers are integrating datacenters into their networks to create services that involve processing and storage processing and result in a unified datacenter-carrier network model. Service providers are required to increase ARPU while reducing CapEx and OpEx through hardware consolidation, network resource optimization and ease of service deployment, all key factors in accomplishing this. Virtualization is a proven technology adopted universally in datacenters for resource optimization and scalability. By extending virtualization principles to the carrier networks, service provider can achieve end-to-end optimization in the integrated datacenter-carrier network. NFV and SDN enable virtualization in different segments of a datacenter-carrier network. SDN allows network functions and applications to leverage virtualized datacenter resources, while using NFV and SDN, carriers can scale to deploy innovative services and increase subscriber base within CapEx and OpEx budgets.
