What is Software-Defined Networking (SDN)?

By IBM Services

SDN Versus Traditional Networking Explained

 

What are the benefits of software-defined networking (SDN) and how is it different from traditional networking?

When it comes to creating their own networks, every enterprise has to weigh the pros and cons of the different network types. With increased consumer demands for performance and flexibility, some cons quickly become heavier than others.

Along with the growing needs of modern networks, the biggest cons of maintaining traditional networks have bolstered the ascendancy of SDN. SDN solutions and other virtualized solutions are burgeoning. Globe Newswire argues that the SDN market will reach USD 59 billion by 2023.(1)

Physical infrastructure, especially hardware that requires manual configurations, simply hasn’t been able to keep pace with modern technology. The ballooning demands that modern enterprise users require are too much for most traditional networks. Users looking to upscale their network infrastructures with as little disruption as possible quickly turn to SDN.

 

What’s SDN?

SDN is defined by “the decoupling of control and packet forwarding planes in the network”.(2) It enables networks to directly connect to applications through application programming interfaces (APIs), bolstering application performance and security, and creating a flexible, dynamic network architecture that can be changed as needed.

Arguably, the most frequently used means for application deployment, SDN is used by enterprises to deploy their applications faster while also cutting the overall deployment and operating costs. IT administrators using SDN can manage and provision their network services  from a centralized point.

A network paradigm that yields programmatic management and control, and network resource optimization, SDN applies open APIs to help maintain network control. This network control is created when SDN decouples the network configuration and traffic engineering, separating them from their fundamental hardware infrastructure.

This parting allows the use of OpenFlow and other open protocols. These open protocols can access network switches and routers that often use proprietary and otherwise closed firmware by applying globally aware software control at the network’s edge.

 

The control plane and the data plane, and early SDN implementation

SDN helps users virtualize their hardware and works to create a computer network by breaking down the network into the following separate planes:

  1. The control plane offers the performance and fault management of NetFlow and, like protocols, is frequently used for managing device configurations that are remotely connected to a software-defined network.
  2. The data plane forwards traffic to its desired destination. Before traffic reaches the data plane, the control plane dictates what path flows it will take by using the flow protocol— when a network administrator works with the software-defined network and manages the network.

When it was first deployed by large enterprises, such as Google and Amazon, SDN helped them create scalable data centers, facilitate network resources and new server expansion, and reduce the workload for IT administrators. SDN optimized the efficiency of the upscaling process for these large companies and quickly drew the attention of other large companies who swiftly adopted SDN to improve their upscaling efficiency.

 

What’s a traditional network?

Traditional networking is rooted in fixed-function network devices, such as a switch or router. These devices each have certain functions that operate well together and support the network. If the network’s functions are implemented as hardware constructs, then its speed is usually bolstered.

Flexibility is a recurring hurdle for traditional networks. Few APIs are exposed for provisioning and most switching hardware and software is proprietary. Traditional networks often work well with proprietary provisioning software, but this software can’t be quickly modified as needed.

Traditional networking consists of the following traits:

  1. The functions of traditional networking are primarily implemented from dedicated devices using one or more switches, as well as routers and application delivery controllers.
  2. The functionality of traditional networking is largely implemented in dedicated hardware, such as application-specific integrated circuits (ASIC). One of the negative aspects of this traditional hardware-centric networking is its limitations.  

What are the differences between SDN and traditional networking?

The most notable difference between SDN and traditional networking is that SDN is software-based while traditional networking is usually hardware-based. Because it’s software-based, SDN is more flexible, allowing users greater control and ease for managing resources virtually throughout the control plane.

Inversely, traditional networks use switches, routers and other physical infrastructure to create connections and run the network.

SDN controllers feature a northbound interface that communicates with APIs. Because of this communication, application developers can directly program the network, as opposed to using the protocols required by traditional networking.

SDN lets users use software to provision new devices instead of using physical infrastructure, so IT administrators can direct network paths and proactively arrange network services. Unlike traditional switches, SDN also has the ability to better communicate with devices using the network.

Virtualization epitomizes the primary difference between SDN and traditional networking. When SDN virtualizes your entire network, it generates an abstract copy of your physical network, and lets you provision resources from a centralized location.

Opposingly, with a traditional network the physical location of the control plane hinders an IT administrator’s ability to control the traffic flow.

With SDN, the control plane becomes software-based, allowing it to be accessed through a connected device. This access lets IT administrators manage traffic flow with greater detail from a centralized user interface (UI). This centralized location grants users greater control over how their networks work and how their networks are configured. The ability to quickly process different network configurations from a centralized UI is especially beneficial for network segmentation.

SDN became a popular alternative to traditional networking because it lets IT administrators provision resources and bandwidths as needed without requiring an investment of additional physical infrastructure. Traditional networking requires new hardware to increase its network capacity. The paradigm for SDN versus traditional networking could be distilled to the generalization: one requires more equipment for expansion and the other requires only keystrokes.

 

What are the primary advantages of SDN?

SDN has the advantage of generating a framework that bolsters data-intensive applications, such as big data and virtualization. Big data and virtual machines are somewhat intertwined. Ingram Micro argues that “Virtualization adoption is being driven by big data and SDN provides the means to manage virtual machines and big data network traffic.”(3)

In addition to centralizing and simplifying the control of enterprise network management, SDN offers the following succinct advantages:

  • Traffic programmability
  • Greater agility
  • Capacity to generate policy-driven network supervision
  • Ability to implement network automation

Here are several of the primary advantages that SDN offers:

  1. Centralized network provisioning. SDN helps centralize enterprise management and provisioning by offering a unified perspective on the whole network. SDN can also speed up service delivery and boost agility in provisioning virtual and physical network devices in a central location.
  2. Holistic enterprise management. Networks must meet the rising demand for processing requests. SDN helps your IT department adjust your network configuration with no impact on your network. Also, unlike Simple Network Management Protocol (SNMP), SND bolsters the management of physical and virtual switches and network devices that are from a central controller.
  3. More granular security. Virtual machines pose a challenge for firewalls and content filtering, a challenge that’s further compounded by personal devices. By establishing a central control point for regulating security and policy information for your enterprise, the SDN controller quickly becomes a boon for your IT department. 
  4. Lower operating costs. Several benefits to SDN, such as having an efficient administration, server utilization improvements, and improved virtualization control, can dually help cut operating costs. Because many regular network administration issues can be automated and centralized, SDN can also help reduce operating costs and grow administrative savings. 
  5. Hardware savings and reduced capital expenditures. SDN adoption helps revive older network devices and simplifies the process of optimizing commoditized hardware. By following the instructions from the SDN controller, older hardware can be repurposed while less costly hardware can be deployed to optimal effect. This process allows new devices to become veritable “white box” switches that have intelligence focused at the SDN controller.
  6. Cloud abstraction. Using SDN to abstract cloud resources helps simplify the process of unifying cloud resources. SDN controllers can manage all the networking components that comprise the massive data center platforms.
  7. Consistent and timely content delivery. One big benefit of SDN is the ability to manipulate data traffic. It’s easier to have quality of service for Voice over Internet Protocol (VoIP) and multimedia transmissions if you can direct and automate data traffic. SDN also helps with steaming higher-quality videos since SDN bolsters network responsiveness and, therefore, creates an improved user experience (UX). 

 

Why are companies transitioning to SDN from traditional networks?

In addition to its many benefits, here are several other reasons why data enterprises are opting for SDN over traditional networking:

  1. Today’s users demand the untethered access to infrastructure, applications and IT resources. This demand comes as a result of the proliferation of cloud services, which necessitates additional storage, computing and bandwidth.
  2. The advent of bring-your-own-device in the workplace requires dynamic and flexible networks. These networks must also be security rich and capable of protecting data and assets, and meeting compliance regulations and standards. Because it adheres to product cycles and vendor-specific environment proprietary interfaces, traditional networking is unable to meet these demands. Traditional networking tends to be rigid, making it difficult for network operators and administrators to customize the programming of their networks. The process of adding devices or increasing network capacity is cumbersome and time-consuming, necessitating hands-on access for each console and device.
  3. SDN lets network operators and administrators adjust their resources and bandwidths as needed, providing data centers with boosted efficiency, malleability and resiliency. Also, SDN doesn’t require investing in physical infrastructure and isn’t largely capable of being automated, which further bolsters the chances of enterprises to cut costs and improve network performance.

 

SDN infrastructure versus traditional network infrastructure

The rise of cloud computing and the increased demand for mobility and remote collaboration is putting more pressure on traditional enterprise networks to perform like cloud networks. For enterprises with these traditional networks, this situation often results in slower innovation, development and production.  In the IBM white paper, Software-defined networking in the new business frontier, the author argues that “Traditional network architectures that are too old, rigid and expensive to scale are out of alignment with today’s hybrid cloud (a combination of traditional, public and private cloud infrastructure) and IT as a service (ITaaS) deployments.”(4) Networks that are automated and optimized within a virtualized and hybrid IT environment are more likely to help enterprises produce greater innovations and reductions in cost and complexity.

For traditional network infrastructure, each switch determines where traffic goes and then directs the traffic based off of these determinations. With SDN infrastructure, the process of determination and direction has been decoupled. Switches still direct the traffic, however the process of determining where the traffic goes is performed by an automated programmable interface. Also known as an SDN controller, this centralized control point automates network management and control and has oversight into all of the SDN’s nodes.

Performed from a centralized control point that integrates the information and weaves the network switches together into a single unified platform. This platform allows network administrators to change network-wide settings with a centralized console. Whereas traditional network infrastructure might warrant deploying network changes in a piecemeal fashion for individual devices, the centralized console of the SDN’s infrastructure helps streamline the process of performing network changes. With the centralized console, the software is able to deploy necessary network changes cohesively and uniformly to all necessary devices. Multivendor switching equipment can also deploy any necessary changes using a single interface.

The IBM white paper states that “[SDN answers] the need for agility, scalability and visibility by transforming hardware-intensive legacy networks into fully programmable, virtualized [SDN] that streamline operations and the delivery of new services”4. SDN infrastructure gives network administrators the flexibility to change network traffic and enables network resource deployment that scales at the same speed as server and storage, redirecting it as needed. Additionally, the SDN controller reduces complexity and enables the network to scale as needed. The benefits of SDN are that it can help enterprises promote innovation and development and accelerate time to market for applications and services.

 

Overlay virtualization, fabric-oriented virtualization and network function virtualization

Network virtualization is essential to SDN. SDN virtualizes and abstracts networks services, such as security, constructs and segmentation, from the physical network infrastructure, then defines these network services in software. This process makes the network programmable. 

Network virtualization’s benefits include increases flexibility, cost savings, and increased agility and scalability, and allows isolation between preventing interactions between adjacent test and production environments. In the event if a cyber attack, network virtualization is a crucial tool for containing security threats and maintaining data privacy throughout multitenant environments.

Virtualizing networks requires one of two approaches:

  1. Overlay virtualization, often considered the most cost-effective and popular approach, creates virtual overlay networks, also known as software abstractions, on top of the existing physical networks. Overlay virtualization can be deployed gradually as needed and with no changes to the physical network.
  2. The fabric-oriented approach strives to operate the network hardware, also known as fabric, with greater efficiency and programmability. Often performed as part of a major refresh, this approach involves purchasing or modifying new physical switches.

These virtual networks and the applications that run on them are logically isolated. This isolation allows these virtual networks and their applications to be individually managed and programmed.

Virtual networks accelerate time to market for new applications by allowing the creation of identical virtual development, testing and production environments. Network function virtualization (NFV) is a third approach that is specific to function virtualization, as opposed to network virtualization. NFV deploys these virtualized network functions (VNF) as software onto virtual machines instead of running these functions on dedicated network appliances. NFV reduces cost by allowing network functions to run on standard commodity hardware and makes the virtualized functions more accessible for the applications that need them.

These three approaches are complimentary and can be used together or individually. As an architectural approach, SDN optimizes what overlay, fabric oriented and NFV can produce. SDN provides the dynamic orchestration and intelligence that continually improves the utilization and delivery of virtualized network resources (VNR) and the flow of data across the network infrastructure.

 

SDN versus SD-WAN

Because of their similarities, SDN is often compared with software-defined wide area networks (SD-WANs). By using broadband and Multiprotocol Label Switching (MPLS), SD-WAN  lets enterprises connect different locations. SDN is meant to function on local area networks (LANs) and is used for creating networks that can be speedily modified as needed. SD-WAN is meant to produce a wide area network (WAN) that links several sites together and support a WAN for a broad geographical spread.

Similar to SDN, a SD-WAN eliminates the need for maintaining lots of network hardware. Additionally, a SD-WAN can be used from an software defined network where it offers the geographical capabilities of a SD-WAN along with the flexible capability of SDN to be configured as needed.

Also, SDN is configured by the IT administrator or the user, while vendors control a SD-WAN service. Because users aren’t responsible for offering the service, an SD-WAN tends to be easier to deploy.

 

What are the benefits of 5G SDN?

SDN can be defined as a separate approach from traditional networks and how they are designed, built and managed. An alternative approach to traditional networking, SDN separates the network’s control and forwarding planes. This approach enables the direct programmability of the network control and allows the subsequent infrastructure of SDN to be abstracted for network services and applications.

SDxCentral says that “SDN is redefining the network architecture to support the requirements of the forthcoming 5G ecosystem—5G SDN will play a crucial role in the design of 5G wireless networks.”(5) The 5G SDN model should allow greater flexibility and programmability for 5G networks.  

5G SDN produces immense value when combined with NFV and VNF, a combination that helps it to provide automation, network virtualization and new services separate in addition to virtualized resources. 5G SDN architecture is dynamic, easy to manage and cost-effective and 5G SDN network programmability enables new business paradigms and propels revenue growth.

 

What’s an SDN application?

In its article, What is Software-Defined Networking (SDN) Application?, Lavelle Networks eponymously notes that an SND application “is a software program which is designed to perform a task in a software-defined networking environment”6. This computer networking approach both helps network administrators to make systematic changes through open interfaces and potential lower-level functionality. Another benefit of SDN applications is that they boost functions “that are accomplished in the hardware devices of a regular network through firmware”(6) by enlarging and subsisting upon them.

SDN helps administrators manage the entire network using high-level functionality abstraction. Despite management abstraction, there must be some communication between the control plane and the data plane. The control plane manages traffic distribution and directs where traffic is sent, and the data plane is the underlying system that helps control the destination of the traffic.

 

What’s Open Daylight?

A modular open platform for automating and customizing networks regardless of scale or size, Open Daylight (ODL) came from the SDN movement and the drive for network programmability. Created as a foundation for commercial solutions to address different use cases in today’s network environments, ODL functions as an SDN controller platform for both internal and external SDN applications.

 

Internal SDN applications

Applications that host the ODL controller software and get deployed internally are run from inside the container, and must be scripted in Java, the native language of ODL. Internal SDN applications must follow the controller’s established design and execution constraints and implement them in the controller’s Java Virtual Machine (JVM). These internal SDN apps can access the model-driven service abstraction layer (MD-SAL) applications and Java application programming interfaces (API) of the controller that’s running inside the Open Services Gateway Initiative (OSGi) Alliance container of the controller.  

 

External SDN applications

Inversely from internal SDN applications, external SDN applications are applications that host the rest of ODL controller software but get deployed externally and are run remotely from outside the container, sometimes using a different host than their controller. Unlike internal SDN applications that require ODL’s native language, external SDN applications allow the use of any scripting language when writing them. External SDN applications use the app that provides them with RESTful access for their services and the Representational State Transfer (REST) API that their controller provides for them.

 

IBM can help

For anyone looking to get started on the journey to the cloud, SDN can be a key component that helps you transform your sluggish network into a nimble connector. IBM can help your enterprise break free from its cumbersome hardware constraints and gain improved agility, security, flexibility and programmability.

With a consulting-led approach that helps build cloud-enabled, dynamic, resilient networks for your future business needs, IBM SDN Services provides offerings that are customized for your enterprise.

IBM SDN services helps enterprise customers create a highly programmable network spread that stretches through data center and cloud software-defined network-data center (SDN-DC), wide area network SD-WAN and branch networks (SD-LAN).

For more information about SDN and how it can help your business, schedule a one-on-one meeting with an IBM expert at no cost. IBM is here to help you move your business forward with confidence.

 

Sources

  1.  Software Defined Networking (SDN) Market Size USD 59 Billion by 2023 Growing at Massive CAGR of 42.41% Globe Newswire, 4 April 2019.
  2. SDN vs Traditional Networking: Which Leads the Way? Fiber Optic Cable Solutions, 22 December 2018.
  3. 7 Advantages of Software Defined Networking. Ingram Micro, 8 August 2017.
  4. Software defined networking in the new business frontier. IBM.com, November 2016.
  5. How 5G SDN Will Bolster Networks. Sdxcentral, 31 October 2017.
  6. What is Software-Defined Networking (SDN) Application? LavelleNetworks.com, 27 April 2018.