Learning OpenDaylight
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SDN use cases

This topic is very crucial, as in many cases stakeholders think why do they have to invest in SDN? What can SDN provide that the legacy network cannot? That's a valid question to ask.

There are multiple good use cases where SDN can add value:

  • A network operating system: The SDN platform can act as a network operating system, providing packet delivery to other applications. SDN is a platform and allows other applications to drive, use the network for their specific requirements. Always remember that SDN doesn't do any packet delivery on its own, but it requires SDN applications (many of them) to define how packets needs to get delivered in a network.
  • Network Access Control: One of the SDN use cases is NAC. The SDN controller can identify the newly connected devices and checks what this new device is, and what it needs to access and push the flow settings back to the SDN enabled switches. This method eliminates the use of 802.1x and VLAN assignments.

This diagram illustrates the use of SDN to enforce Network Admission Control (NAC) :

  • Anycast applications: Anycast applications are referred to as distributed systems, which are built with multipole service nodes in a network. For example, streaming servers and file and object servers. With the change of the way application servers are built to a scale-out model, most modern service applications architecture is based on a distributed scale out model that all operates independently. An SDN platform is able to deliver the user requests to the closest, or better saying the best service node of an application. Other than being close there are other parameters such as load, bandwidth, and data availability. As an example an object storage platform might have multiple service nodes distributed in different location in the network and all working at the same time, using a single IP address. SDN networks will be able to understand where the service nodes are located (connected to which switch at what port) and will route the client requests to a particular network node that is considered as its best choice based on different parameters.
  • Integration with private cloud (VMware, OpenStack): With increased use of VMware vSphere and OpenStack in data centers, the need to integrate the network with cloud infrastructure is increasing. An SDN network can get integrated with cloud application and provide the ability to create virtual networks, tenant isolation, and even create overlay networks using VXLAN. Also it can support service chaining to insert L4-L7 services.

The controller is the key component to integrate with cloud application via APIs.

  • Virtual CPE and virtual CE: In a service provider environment, normally service providers install a dedicated router in each customer premises, which is always a rigid expensive box forced to clients. With the introduction of SDN, many service providers found this momentum and started using the opportunity window in order to build their SDN CPE, moving out from a dedicated router, replacing it with a commodity hardware (x86), which can run multiple virtual machines for network functions virtualization (NFV). AT&T and NTT have been successful in this area while others such as Verizon are also building their portfolio. Using SDN, the service provider will be able to use an edge SD-WAN enabled virtual machine to connect the customer to the network.

Another change in WAN and SD-WAN is the increase of reliability of consumer grade Internet connections. Many organizations prefer to use multiple cheap, high bandwidth Internet links instead of using an expensive limited bandwidth MPLS connection from their service provider. To answer this trend, which leads to popping up of SD-WAN products and vendors, service providers started to standardize a provisioning method of delivering an MPLS link and a (or more) Internet links to clients, which is called local Internet breakout. SD-WAN utilizes the local Internet breakout to build a secure tunnel to service provider networks and runs an SDN software with enough intelligence to understand what traffic should be routed via MPLS and via the Internet link.

SD-WAN is currently started to boom and there are many vendors such as Silver Peak, Riverbed, VeloCloud, Citrix, and so on, providing competitive and interesting products to enable enterprises to reduce their WAN costs and increase the quality of services.

  • Service providers: In a service provider network where there are multiple geographical routers to provide backbone connectivity to clients, an SDN enabled network allows injecting and overriding the policies over the provider routers. In service provider networks the southbound protocols are normally BGP-PCEP, which is being promoted and used in many SP proof of concept installations. With SDN, a service provider will be able to override the MPLS or BGP decisions and route the specific traffic in a different way other than what has been determined by routing protocol. Cisco has done some progress in this area, remember that Cisco is one of the contributors to OpenDaylight and in fact the ODL web interface (Next) is donated by Cisco. You can find the Cisco service provider SDN example here:

https://github.com/CiscoDevNet/opendaylight-sample-apps

https://developer.cisco.com/site/opendaylight/discover/odl-at-cisco/build-apps-on-top-of-odl/

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