Open Network Featured Article

The growing popularity of software defined networking (SDN) in the data center has resulted in a number of benefits, including speeding up service deployments. The ability to rapidly provision new services in an open and efficient networking environment is one of the compelling arguments for SDN deployments.

The OpenFlow communications protocol is a key component when it comes to data center SDN deployments, handling tricky issues like dynamic provisioning, interconnection and fault management. A recent DatacenterDynamics article discusses the importance of OpenFlow in the widespread use of SDN in the data center and beyond.

Very simply, OpenFlow gives access to the forwarding plane of a network switch or router over the network, enabling controllers to determine how packets will travel across the network. By separating control from forwarding, traffic management is handled much more efficiently. OpenFlow also supports interoperability among different switches from different vendors, in the true spirit of SDN.

Within the data center, SDNs that use OpenFlow are implemented in ‘tenary content-addressable memory’ (TCAM). While this was initially a barrier to OpenFlow adoption, since early switch ASICs contained small TCAMs, they have begun to grow to meet the vigorous demands of SDN. But TCAMs are both power hungry and expensive, and are also difficult to scale, presenting an issue when it comes to OpenFlow usage and adoption.

The latest OpenFlow 1.4 protocol addresses these limitations by supporting table type patterns (TTP). TTPs essentially allow OpenFlow to access a variety of ASIC tables in addition to TCAM for routing traffic. By using VLAN, MAC and IP in addition to TCAM, OpenFlow enables SDN apps to freely scale across ASIC architectures. The latest version of the protocol uses bundle messages, eviction and vacancy events and synchronized tables to improve flow management. The result is better and more efficient scalability of SDN applications, with support for up to two million flows in some instances.

Software and hardware developers are now working on switching products that take advantage of OpenFlow’s evolution and support SDN. As the industry continues to move toward SDN in the data center and beyond, OpenFlow will continue to play an integral role in automating and controlling traffic management.