Demystifying Software Defined Networking

Software Defined Networking (SDN) is a trending topic these days. It is a movement which will have a large implication on how data center and enterprise networking will be built and managed. This article covers the history of SDN and how it is disrupting the traditional networking models by bringing the cost down.

Networking industry has traditionally been building vertically integrated stacks based on proprietary components. This seriously limited innovation, as it was difficult for researches to simulate network topologies.

Researchers at Stanford built a prototype platform Ethane, which tried to loosen the data and control planes of the networking stack. This model helped configure the network from a central plane.

This formed the basis of Software Defined Networking where network routing is configured in software using high-level languages such as Python or Java and pushed down to the underlying switch.

SDN has helped transform Vertically integrated Network stacks into programmable loosely coupled Control and Data planes. 

OpenFlow is a standard introduced to decouple controller and switch interaction. This means the networking stack is not tied to a particular switch or a controller vendor. Controller and the switch interact using Open Flow Standard.

Some of the key players in this field are:

• Nicira (Called NSX after acquisition by VMware): Nicira is one of the pioneers in SDN, born out of Martin Casado’s Research project at Stanford, it helped refine and implement the SDN stack which works across various cloud orchestration layers including, OpenStack, CloudStack and vSphere. Nicira has also implemented an open source virtual switch called Open vSwitch, which is one of the key components of its SDN implementation.
• Big Switch Networks: Big Switch Networks is considered another key player in this space. Big Switch SDN offering is partially open sourced in the form of Flood Light Controller project. This project is an effort to get community involved in its SDN implementation efforts.
• Cisco: Cisco rolled out its SDN offering called Cisco Open Networking Environment. Cisco’s approach is tied closely to its hardware offerings but offers central controller concept similar to other traditional players. It is also investing heavily in Open Daylight open source SDN effort.
• Open Daylight: This is an open source project which is a part of Linux foundation. This project is supported by Cisco, Citrix, Redhat, Brocade Networks among others. The goal of this project is to build an Open Flow SDN stack which is open source. Big Switch Network had a rather public spat with Cisco on the control of the project and decided to step down.

Impact of SDN on Cloud service providers

SDN will potentially have a very positive impact on operational efficiency as most of the network configuration will be done programmatically using standard tools and protocols (at least south bound APIs). Cloud providers will be able to leverage their existing switching infrastructure but will have to learn and ramp up on new tools and loosely coupled stacks.

Impact on enterprises

For enterprises which have matured beyond basic virtualization and are looking at Private Cloud Deployments, SDN will be a must have as this will allow them to add network and elements provisioning to the automation and self service story.

Challenges in SDN adoption

• Biggest challenge in migration to any SDN stack is the lack of trained professionals as well as lack of knowledge about standards like Open Flow.
• Though South Bound APIs have been standardized as Open Flow, APIs between cloud orchestration layer and the SDN controller are still vendor specific.

To summarize, SDN has taken networking industry out of mainframe mentality and helped spur innovation. There are some new players like Nicira (VMware) and Big Switch Networks who are implementing software-based approach to managing networks. Traditional players like Cisco have a slightly different approach to SDN, which is tied closely to their hardware business. Overall this is good news for Cloud providers and enterprises from network components interoperability and manageability angle.