Planning for SDN
Software-defined networking (SDN) is the hottest thing going today, but there is considerable confusion surrounding everything from the definition of the term to the different architectures and technologies suppliers are putting forward.
Mon, December 02, 2013
Network World — Software-defined networking (SDN) is the hottest thing going today, but there is considerable confusion surrounding everything from the definition of the term to the different architectures and technologies suppliers are putting forward.
Given the confusion, some IT shops are probably taking a wait-and-see attitude. But while that response would be understandable, it isn't the right approach because, even though no reasonable person would claim to know how SDN and network virtualization will evolve over the next several years, there is no doubt these emerging technologies will have a significant impact.
You need to plan now for how you will evaluate and possibly implement these new approaches to networking. We'll outline some macro considerations that you'll need to take into account when you formulate that plan, then outline some micro issues, but let's start with a definition of SDN.
The Open Networking Foundation (ONF) is the group that is most associated with the development and standardization of SDN. As the ONF points out, SDN is not a technology, but an architecture. According to the ONF, SDN decouples the network control and forwarding functions enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. According to the ONF, the OpenFlow protocol is a foundational element for building SDN solutions.
Part of the confusion that surrounds SDN is that many vendors don't totally buy in to the ONF definition of SDN. For example, while the vast majority of vendors do include the centralization of control in their definition of SDN, there isn't agreement as to how much control should be centralized. In addition, while many vendors are viewing OpenFlow as a foundational element of their SDN solutions, other vendors are taking a cautious approach to OpenFlow and in the mean time adopting protocols such as XMPP.
Another source of confusion is the relationship between network virtualization and SDN. It is possible to implement an SDN that resembles the ONF definition of SDN and use the SDN to implement network virtualization. For example, the Open DayLight foundation recently accepted a contribution from NEC referred to as Virtual Tenant Networking (VTN) that enables an SDN to implement network virtualization. It is possible, however, to implement network virtualization without implementing SDN. For example, both Nuage Networks and VMware/Nicira implement network virtualization using an overlay model. To add to the confusion, Nuage Networks refers to its solution as SDN while VMware is adamant that its solution is network virtualization and not SDN.