What Is SDN (Software-Defined Networking)? Complete Beginners Guide
Meta Title: What is Software Defined Networking (SDN)?
Description Meta Tag: Learn what Software Defined Networking (SDN) is all about and get details on SDN architecture, benefits, limitations, and use cases.
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Introduction
In the current scenario, networking has emerged as a very important aspect of most business organizations. Regardless of whether you use your online banking facility, cloud computing, video conferencing or enterprise software application, you need a reliable network that is also secure from any kind of threat. Managing a network using conventional methods is quite hard, particularly when you need to make some configuration changes frequently.
This is where Software Defined Networking (SDN) enters the picture.
Software-Defined Networking (SDN) refers to a networking approach that enables the administrator to control and manage the traffic of the network using software. As such, instead of configuring the individual network components, the administrator will be able to configure the entire network infrastructure via software.
In this article, we shall explore the concept of SDN, its workings, architecture, components, benefits, drawbacks, and applications in networking and cybersecurity.
What Is Software Defined Networking (SDN)?
Software-defined networking is a kind of networking idea that entails the separation of the control plane and the data plane in order to enable the traffic within the network to be controlled using software.
In a normal networking environment, traffic routing occurs using the switches and routers, and the decisions as to how the traffic flows in the network are made. In the software-defined network, the traffic routing is carried out using a software-controlled network.
This makes the networks flexible, programmable, and automated.
For example, take the scenario of having 100 switches in an enterprise located in various locations.
In the traditional setting, there might be a necessity for individual configuration of devices or use of different automation software. The SDN environment will provide the opportunity to deploy consistent policies among compatible devices.
Features may vary depending on the SDN architecture and the hardware involved.
How Does SDN Work?
In order to understand SDN, it is necessary to understand two fundamental concepts related to networks—control plane and data plane.
1. Control Plane
The control plane is the part of the network infrastructure that is used to make decisions about how the traffic will go through the network.
In the case of SDN, control activities can be performed by the SDN controller that interacts with network devices.
2. Data Plane
The data plane is the part of the network infrastructure responsible for sending packets through the network.
In the case of SDN, network devices can get forwarding instructions from the controller and apply them to traffic.
Example: How SDN Handles Network Traffic
magine a corporation that has three departments:
- HR Department
- Finance Department
- IT Department
Now the company would like to allow the IT department personnel to access certain management systems but restrict any other user from accessing finance-related resources.
Using SDN architecture, the same could be done using policy enforcement. The controller will define the right set of policies for the network elements.
In case the policy is updated by the corporation, then the administrator just needs to update the policy via the management system.
It’s an example of how SDN makes network management easier. All depends on the controller, capability of devices used and selected security features.
Architecture of SDN: Key Components
Typically, there are three layers of SDN architecture.
1. Application Layer
The application layer consists of software applications that specify the network requirements and policies.
Some of the examples include:
Network monitoring applications
Security and access control applications
Traffic engineering applications
Network analysis applications
Automation applications
The applications specify their requirements to the SDN controller through northbound interfaces or APIs.
2. Control Layer
The control layer contains an SDN controller, which acts as the network control center for its domain.
It holds information about the network, translates requests of the application to the network commands, and coordinates devices that are supported.
Examples of SDN controllers are Open Network Operating System (ONOS), OpenDaylight and controller software by network vendors.
Despite being conceptually centralized, some implementations of SDN use multiple controllers or even distributed architectures of controllers.
3. Infrastructure Layer
The infrastructure layer includes physical or virtual networking elements like switches, routers, etc.
This layer forwards data packets as per the defined rules.
The infrastructure layer interacts with the control layer using southbound interfaces.
Northbound & Southbound Interfaces
The following two interface types play a crucial role in SDN:
Northbound interfaces: These interfaces enable applications or orchestration systems to provide specifications to the controller.
Southbound interfaces: These interfaces allow the controller to connect to network devices to manage the forwarding behaviors that they support.
OpenFlow is a popular southbound protocol used in earlier SDN architectures. But, SDN is not confined to OpenFlow; other platforms use other protocols and APIs for this purpose.
SDN vs. Traditional Networking
Both traditional networking and SDN have the potential to provide a stable connection. However, the main difference is in terms of network control and configuration.
Feature
Traditional Networking
Software-Defined Networking
Network management
Often device-by-device
Centralized or orchestrated management
Configuration
Manual or automated per device
Policy-driven and programmable
Control plane
Commonly distributed across devices
May be logically centralized
Automation
Depends on available tools
Often a core design capability
Policy deployment
Can require changes across multiple devices
Can apply policies across supported devices
Flexibility
Depends on device features and management systems
Designed to make network changes more programmable
Troubleshooting
May require information from multiple devices
May provide a consolidated view of the managed network
It is crucial to remember that the implementation of SDN will not render all traditional networking protocols irrelevant. Technologies like Ethernet, IP, routing algorithms, and VLAN will continue to be functional despite the usage of SDN.
Advantages of Software Defined Networking (SDN)
1. Centralized Network Management
The use of SDN can allow for network administrators to have visibility of all of their network resources and policies in one place. This will minimize time spent on the management of networks.
2. Automation
Automation is a key benefit of using SDN. Network administrators can make use of software and APIs in order to automate tasks and configuration of the supported infrastructure.
3. Increased Network Flexibility
The business needs may frequently change. For instance, new applications may need to be deployed, and cloud migration or other additions to the staff may necessitate some alterations in the network.
The SDN technology enables the network administrator to change the supported network policies and traffic flows using software, which will make it easier for the network to adapt to the changes.
4. Improved Traffic Management
Using SDN, companies are able to control their network traffic based on the needs of the applications and business needs.
For example, a company may decide to give priority to voice and video traffic over other, less urgent applications.
5. Enhanced Security Policy Management
SDN can provide centralized security policies, segmentation of the network and an automatic reaction to some security incidents.
For instance, upon detection of a compromised endpoint by a security monitoring system, an integrated network management system can isolate the compromised endpoint through updating access policies.
These reactions need appropriate integration, precise detection and well-planned safeguarding measures.
6. Provision of Cloud and Virtualized Environment
Cloud computing is characterized by creation and destruction of virtual machines, containers and application services. SDN will be helpful when it comes to managing connectivity and network policies for changing resources.
It makes SDN relevant to dynamic networks.
Common Uses of SDN
Software Defined Networking is helpful in many networking settings.
Data Centers
Data centers are composed of many servers, switches, and applications.SDN can be applied to automate network configuration and traffic management and segmentation of the workloads.
Software Defined Wide Area Networking (SD-WAN)
The technology of SD-WAN employs the concept of software defined networking to establish a WAN link.
Depending upon the specific SD-WAN solution, it can help choose network paths according to applications, link conditions, and policies.
Campus Networks
Campuses like universities, hospitals, and other organizations may have hundreds or thousands of connected endpoints. Solutions that make use of SDN can help in managing access and policies among other things.
Networking in Clouds
Networks in cloud settings need some form of connection for virtual machines, applications, and other services. Software-defined networks can assist with the management of these connections and network policies.
Security Operations
Software-defined networks can be used together with SOC processes to include networking with security monitoring and response.
For instance, during a security operation investigating a certain communication, it might be necessary to limit access from that device until further investigation is completed. This will depend on the existing integrations and authorizations in place.
SDN and Cybersecurity: What Should Beginners Know?
SDN is crucial for cyber security students since the network programmability feature increases not only the defense capabilities but also the risks associated with the possible misconfiguration.
Imagine a network where there are VLANs for the employees, the server, and the guests. Conventional access control measures would prohibit any communication between these VLANs. An SDN-based system can give even more centralizing options for the policy implementation on the supported devices.
However, the concentration of the management process also involves some risks.
If the intruder will manage to seize the control of the SDN controller or obtain any unauthorized access to APIs, then he can change the main rules of the network.
For organizations to be able to ensure SDN's security, they should adopt:
- Authentication and role-based access control measures.
- Encryption of controller-to-device and management communication if possible.
- Network segmentation of management interfaces.
- Patching and security assessment procedures.
- Administration logging and monitoring.
- Redundancy and recovery plans for the controllers.
- Process of testing and approving of policy modifications.
When SDN is used effectively, it can increase the security of an organization, however, SDN cannot replace firewalls, endpoint protection, identity management or security monitoring.
Challenges and Limitations of SDN
While SDN provides certain benefits, there are certain things that one has to consider while using it.
Implementation challenges: Implementation of an SDN solution within existing network infrastructure might require some preparation and special skills.
Security of the controller: The controller itself and its APIs should be highly secure since they are capable of controlling critical elements of the network.
Availablity issues: Controller outage is likely to impact not only network management but also some network processes (depending on the architecture).
Compatibility: All devices used as a part of network components or having specific features may not be compatible with all SDN solutions.
Required skill set: Besides knowledge about networking, one may need knowledge about APIs, automation, virtualization, and software-driven networking.
Licensing and costs: Licensing, upgrading, additional hardware and training may add up to the cost.
Hence, in order to implement a successful SDN solution, one must have a clear business objective and migration strategy.
How Can You Start Learning SDN?
If you are new to networking or cybersecurity, familiarize yourself with the fundamentals before moving on to more sophisticated SDN implementations.
- Understand basics of networks: It is important for you to understand IP addresses, subnets, VLAN, trunking, routing, switching, and ACL.
- Understand basics of network planes: There are various differences between control plane, data plane, and management plane.
- Understand basics of APIs: APIs enable software to talk to network devices.
- Learn about automation: Understand the basics of programming using the Python language and network automation.
- Learn about SDN technologies: Understand OpenFlow, OpenDaylight, ONOS, and vendor-specific SDNs.
- Setup a lab: Setup your lab using any supported network simulator or virtual lab to understand how a network can be configured using a controller.
- Try out security scenarios: Learn by practicing segmentation policies and access restrictions in a lab setting.
A better way to learn would be to build a small network, connect it and then try out some selected network functions through a controller.
Conclusion
Software Defined Networking is one of the ways how the current network can be managed. The ability to isolate network control from packet forwarding and to have programmable management allows companies to use automation, increase flexibility, and manage network policies. SDN is used in different cases – for data centers, cloud computing, campuses, SD-WAN, and security management.
While it provides all these capabilities, it is crucial to consider such aspects as controller security, availability, compatibility, and costs. It is highly important for network and cybersecurity professionals to know about software defined networks because it is an excellent means through which one can learn network automation.
Knowledge on routing, switching, security and programming will aid one to understand how software defined networks work in practice.
Author:
Dhammdip Sarkate
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Dhammdip Sarkate
Expert trainer and consultant at SevenMentor with years of industry experience. Passionate about sharing knowledge and empowering the next generation of tech leaders.