Down the Rabbit Hole of Software Defined Networking

Nothing ever remains as it is; everything changes and evolves. And with the world changing and relying increasingly on technology, organizations’ needs are expanding, compelling technologies requiring substantially more computing resources, labor, and planning to operate correctly. Experts developed and applied the advantages of software defined networking (SDN) technology to breach that gap.

SDN technology is a networking architecture relying on standardized application programming interfaces (APIs) to quickly allow network programmers to define and reconfigure how data or resources are handled within a network. In layperson’s terms, it is a network controlled by software applications and SDN controllers to manage flow control for improved network management and application performance. Traditional network management, however, relied on consoles and commands that required much administrative overhead and could be tedious to manage on a large scale. 

APIs allow SDN applications (i.e., email systems, cloud computing services, etc.) to interface and reconfigure the network and its components (e.g., switches, racks of servers, virtual machines, etc.) or pull specific data depending on the requirements. 

Intentions, Challenges, and Advantages of Software Defined Networking 

Like all innovations, there were intentions behind the inception of SDN to meet the needs that arose from organizations implementing new technology in their protocols. And like everything else in this world, SDN as a service is not perfect, and while it has its benefits, it does display some challenges. 

Intent behind Software Defined Networking 

The main objective of SDN applications is to reduce the administration overhead of managing networks. This change makes managing networks more adaptable and adjustable through a centralized controller based on the demands or needs. The rave surrounding SDN architecture was due to its potential usage, including: 

• Providing visibility over the network state and enabling service assurance (close/open-loop). 
• Adjusting the network on demand or dynamically to deliver services or meet defined service level agreements (SLA). 
• Configuring the network to enable or disable traffic patterns (i.e., traffic steering). 
• Configuring the network to fulfill the needs of new workloads and automagically enable cross-workload communication. 
• Removing the decommissioned service-specific network configuration and adjusting impacted network elements accordingly. 

Advantages of Software Defined Networking 

Businesses are interested in SDN’s capacity to handle data-intensive applications. Furthermore, this technology offers a long list of advantages that make it extremely attractive to all industries. The main three advantages associated with a software-defined network include:  

• Increased adaptability: SDN architectures separates the control plane (responsible for routing network traffic) from the data plane (responsible for sending data through routers). The high-bandwidth, dynamic nature of today’s applications needs this scalability. 
• Improved use of network resources: SDN as a service can save money on operating expenses (OPEX) through virtual resources. 
• Increased programmability: The lack of vendor-specific protocols or proprietary helps IT teams easily install, protect, and optimize network resources. The control plane is separated from the forwarding plane, making the network easily programmable. 

There are numerous standards and industry-wide development projects involved in Software defined networking implementation. Three are the most common:  

• NETCONF 
• RESTCONF  
• gNMI/gNOI 

NETCONF 

• Provides client-server connection-oriented sessions with Secure Shell (SSH), a network protocol that gives users a secure way to access a computer over an unsecured network. 
• Democratizes YANG as a data modeling language, automating configuration tasks across heterogeneous devices in an SDN. 

• Relies on Remote Procedure Call (RPC) based operations; one program requests a service from a program located in another computer on a network without understanding the network’s details. 
• Standardizes RPCs to query and configure a network element’s configuration/state. 
• Notion of state and datastore: configuration and operation datastore respectfully tracks the declarative requested state versus the actual runtime state. 
• Network monitoring with a notification framework, subscription-based. 

RESTCONF 

• Relies on HTTP methods to implement the equivalent of NETCONF operations. 
• Complies with the RESTful style of the IT industry. 
• Gives the user the liberty to choose between XML or JSON. 
• Creates, reads, updates, and deletes (CRUD) data only in the <running/> datastore. 
• The RESTCONF operations take effect immediately, without the need to be submitted in two phases. 

• Reduces development and maintenance costs through Standard interfaces compatible with multi-vendor devices. 

Challenges of Software Defined Networking 

There are three significant challenges facing organizations looking to implement software defined networking. 

• Security risks: Centralized administration is a single point of failure, so the entire network suffers if it fails. 
• Northbound API standards: There is no standard for northbound APIs. Subsequently, vendors and open-source entities resort to creating different APIs for their SDN controllers, further complicating application development. 

• SDN controller bottlenecks: When an SDN controller has just one instance, it might create setbacks for a network with much traffic, routers, and switches slowing/delaying operations.  

Telecom and SDN 

Telcos saw the opportunity to move the complete vendor stack to a multi-vendor environment, thus, increasing competition within the vendor space. This situation could reduce capital investments as well. Furthermore, implementing SDN reduces operational expenditure by rendering the network programmable and reactive to event/failure through Artificial intelligence (AI) and machine learning (ML). 

Nevertheless, the application is theoretically more accessible and pragmatically complicated. The first hurdle is hiring skilled experts to program the network and build platforms that enable overall orchestration and control. This situation would require the skills of a software architect and a developer, which is rare and quite expensive. In addition, telecom companies aim for an interoperable multi-vendor environment. As a result, they stopped utilizing the software suite provided by the vendors to manage the end-to-end services provided by their solution. Supporting and managing the integration of the various vendor network elements transfers to the company instead of the vendor. 

Final Thoughts  

Software defined networking implementation has been a savior for programming. It relies on APIs to handle data and resources in a network. At first, the main reason for developing and implementing such technology was to reduce the administrative workload that accompanies network management. From there, experts realized the advantages of Software Defined Networking. three advantages associated with a software-defined network include improved network resource use and increased adaptability and programmability. However, nothing is without flaws. This networking architecture presented many obstacles, chiefly security risks, Northbound API standards, and SDN bottlenecks. Furthermore, the telecom sector has benefitted most from this technology as it transferred the complete vendor stack to a multi-vendor environment. While this switch was not without hiccups, SDN’s use in the telecommunication industry is still ongoing.  

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