What is the OpenFlow protocol and how does it affect my data center's network?
As modern businesses deal with larger amounts of increasingly sophisticated data, the underlying efficiency of the data center network is becoming problematic. Switches and routers have traditionally used standardized protocols such as Open Shortest Path First, Routing Information Protocol and Intermediate System-to-Intermediate System to move traffic packets across the network, but as more workloads compete for limited bandwidth, the emphasis is shifting toward greater traffic efficiency. The emerging OpenFlow protocol aims to provide this efficiency.
A critical part of switch-and-router design is the ability to decide where a packet needs to go and quickly send it to the proper destination. This requires network equipment that can manage a control pathway and a data pathway on the same device, which most do. For example, a switch looks at a packet, decides where the packet needs to go and forwards the packet accordingly.
The OpenFlow protocol's communications approach allows both of these functions to be physically separated. The OpenFlow-compliant switch would still handle packet forwarding, but the switching/routing decisions are offloaded to a separate OpenFlow controller. The controller would then communicate with switches and other equipment using the OpenFlow protocol. The protocol defines detailed messages to perform tasks such as "send packet" or "modify forwarding table," and it defines status messages such as "packet received" or "get statistics."
When an OpenFlow switch receives a packet that it knows how to route, it will simply forward the packet accordingly. If the switch does not yet know how to handle a packet, it will forward the packet to the OpenFlow controller to make a forwarding decision -- or even elect to drop the packet -- and send that decision back to the switch for future use. OpenFlow is an underlying technology needed to enable software-defined networking.
The goal of OpenFlow is to allow the development of creative and efficient routing and switching protocols for the data center network. It provides an enterprise with more versatility and networking options than might otherwise be available with traditional networking equipment using access control lists and conventional routing protocols. OpenFlow is sometimes used in situations that involve VM migration, mobility or network security along with already-established traffic types such as streaming media, storage or Voice over Internet Protocol.
This was first published in May 2013