OpenFlow

OpenFlow. It is a communications protocol that enables the software-defined networking paradigm by providing an open standard for programming the forwarding plane of network devices, such as switches and routers. Originally conceived at Stanford University, it allows the control plane to be separated from the data plane, centralizing network intelligence and enabling more flexible, programmable management of network traffic. This separation facilitates innovation and automation in network infrastructure, moving beyond traditional, vendor-specific configurations.

Overview

The core principle is the decoupling of the network's control logic from the physical hardware that forwards data packets. In a traditional network architecture, each device like a Cisco switch or Juniper Networks router runs its own integrated control and forwarding software. It enables an external controller, often running on a standard server, to dictate the flow tables that govern how traffic is handled by compliant switches from vendors like Hewlett Packard Enterprise or NEC Corporation. This architecture is fundamental to modern data center designs and supports advanced network functions like network virtualization and load balancing.

Technical details

An OpenFlow-enabled switch contains one or more flow tables that perform packet lookups and forwarding. Each flow entry in these tables consists of match fields, instructions, and counters. Match fields can inspect various header elements such as those from the Ethernet frame, IPv4 or IPv6 addresses, TCP ports, or Virtual Local Area Network tags. When a packet matches an entry, the associated instructions are executed, which may include forwarding the packet to a specific port, modifying the packet header, or sending it to the controller via a secure Transport Layer Security channel. The protocol communicates over a secure channel using the official port 6653, with earlier versions using port 6633, and messages are formatted using Protocol Buffers.

Applications and use cases

It is widely deployed in academic and research networks like Internet2 and GEANT for experimenting with novel routing protocols. Within commercial cloud computing environments, such as those operated by Google and Microsoft Azure, it enables dynamic, scalable network provisioning for multi-tenancy. It is also crucial for implementing network functions virtualization, allowing services like firewalls and intrusion detection systems to be deployed as software. Furthermore, service providers use it for traffic engineering in wide area networks and for creating scalable software-defined wide area network solutions.

History and development

The protocol originated from a research project at Stanford University led by Nick McKeown and Martin Casado around 2008. Their work, which included the Ethane project, demonstrated the benefits of centralized network control. To promote and standardize the technology, the Open Networking Foundation was founded in 2011 by major companies including Google, Facebook, and Microsoft. The ONF now maintains the specification, which has progressed through multiple versions, with significant contributions from members like Nippon Telegraph and Telephone and Deutsche Telekom. Early adoption was seen in backbone networks like GENI and has since influenced broader industry standards.

Related standards and protocols

While a pioneering protocol, it exists within a broader ecosystem of software-defined networking technologies. The Internet Engineering Task Force has developed related standards such as Forwarding and Control Element Separation and the Network Configuration Protocol. For southbound communication, alternatives like OpFlex from Cisco Systems and Open vSwitch Database Management Protocol have emerged. Northbound interfaces, which connect the controller to applications, often utilize REST APIs. Other important related frameworks and protocols include OpenDaylight, Open Network Operating System, and the Path Computation Element Protocol for traffic engineering.

Category:Network protocols Category:Software-defined networking