With cloud computing architectures taking center stage in future data center designs, last week’s Open Networking Summit in Santa Clara, CA has highlighted the next tsunami that is hitting the industry: Software Defined Networking (SDN).

Wikipedia defines Software Defined Networking (SDN):

“Firmware of network switches and routers ("control plane") have traditionally remained proprietary, locked and under control of companies that manufactured the equipment. SDN seeks to change this disposition, and to make of firmware of the switches and routers ("control plane") remotely accessible and remotely modifiable via third-party software clients, using open protocols such as OpenFlow.”

One trend that is driving the fire behind SDN is network virtualization. While the server and storage side virtualization initiatives have made good progress, the network space has been lagging behind in innovation. This is about to change.

Software-defined networking essentially replaces much of the equipment and hardware used for controlling the network with an API, thus giving administrators more flexible control over the network while also eliminating much of the hardware investment previously required to do so. While there are many mechanism to service SDN ranging from command-line interfaces (CLI), Simple Network Management Protocol (SNMP), Extensible Messaging and Presence Protocol (XMPP), Network Configuration Protocol (NETCONF), Openstack (Quantum Project), virtualization software APIs such as VMware’s vSphere virtualization product , OpenFlow is by far the most talked about with great promise for the future of networks. OpenFlow is a protocol and an open source API that enables multivendor switches and routers to be programmable through software on a central control element. It is designed to manage and direct traffic among routers and switches from various vendors by separating the programming and routers and switches from the underlying hardware. Aside from SDN and OpenFlow bringing efficiency, agility, scalability and simplicity advantages into the datacenter, the true genius of the approach is the separation of data and control plain so that SOA-based application developers can layer applications onto the network via a software ecosystem. This will open up networks to more innovation by providing a level of abstractions, or virtualization, between network control and physical infrastructure. The advantages are enormous:

* Entire ecosystem is ripe for disruption: Monitoring, Security, Management.
* SDN APIs, OpenFlow will unleash a new wave of innovation.
* Marketplace (App Store) for OpenFlow and SDN apps. Standard,
secure, risk-free, Off-the-shelf networking applications for
every need From QoS, PBR, to Identity Management, Mobility
Management (example fine-grained policy for BOYD), Multi-
tenancy, next generation firewalls and many more.
* Write or procure own software to create or offer unique new
classes of datacenter or hosted services.
* New features can be added through software.
* Controller vendors eventually become app developers, apps come in
free, premium and freemium models.
* Once a network is defined in software it can be much easier to
manage and scale.
* Enable network virtualization and agility to drive up server
utilization, mitigate requirement on expanding or building new
datacenters.
* Enable more enhanced auditable network isolation, collapse
isolated domains and simplify compliance.
* Using SDN leverage policies, templates or profiles to define
traffic flows on network.
* Provide increased consistency of user mobile experience by enable
dynamic roaming between cellular and Wifi for cellular offload.
* SDN enables and enhanced workload mobility, data center
migrations and higher level of redundancy.
* Troubleshooting is simplified in an abstracted environment.
* Rapid service provisioning - simplified and quicker.


There are two groups that are promoting SDN and Openflow : ONRC and ONF. The Open Networking Research Center (ONRC) is focusing on the research side and has amongst its SDN power influencers Nick McKeown of Stanford University and Scott Shenker of UC Berkeley as ONRC's faculty directors. The ONRC, which is developing "a comprehensive intellectual framework" for software-defined networking consist of research groups at Stanford and UC Berkeley as well as an independent, nonprofit Open Networking Laboratory led by Stanford's Parulkar that is developing an open source SDN infrastructure.

Complementary to ONRC, there is an industry group called the Open Network Foundation (ONF), that is promoting the use and interoperability of OpenFlow SDN enabled switches. Its focus is on the commercialization of the standards to the masses. The open source OpenFlow project stems from a years-long research collaboration between Stanford and UC Berkeley.The Open Networking Foundation (ONF), led and represented by leading cloud-service operators, released Version 1.1 of the OpenFlow protocol on February 28, 2011. OpenFlow version 1.2 was approved and published in February 2012. The ONFs and its 66, and counting, member companies have put their commitment behind the standard and its board of directors is the who-is-who in the industry:

Urs Hoelzle (Sr. VP, Engineering, Google)
Najam Ahmad (Director, Network Engineering, Facebook)
Adam Bechtel (VP, Infrastructure Group, Yahoo)
Clyde Rodriguez (GM, Windows Azure Networking, Microsoft)
Stuart Elby (VP, Network Architecture, Verizon)
Axel Clauberg (VP, IP & Optical, Deutsche Telekom)
Yukio Ito (Sr. VP, Services & Infrastructure, NTT Communications)
Nick McKeown (Professor, EE and CS, Standford)
Scott Shenker (Professor, EECS, UC Berkeley and ICSI)

SDN and Openflow has many positive promises in the way how future networks are built, how future networks are managed, and how the rest of the infrastructure interacts with the network. While there is significant support from many vendors, there are some current incumbent networking vendors who been less forthcoming about their SDN plans. The general thinking goes that SDNs could threaten legacy equipment, and profit margins, for some established players. The current landscape for SDN ecosystem vendor is comprised of players in the Application/Services/SDN Controllers such as BigSwitch, Nicira, NEC, Embrane, ConteXtreme and switch infrastructure vendors Arista, HP, IBM, Juniper, NEC, Netgear, Pica, Open vSwich. Future entrants that will join the playground will be, but not limited, to Armour, Brocade, Cisco, Dell, Cumulus Networks, Ericsson, Lenerate Systems, Plexxi, Vyatta.

Urs Hoelzle, a Google executive in attendance at last weeks Open Networking Summit, gave a rare peek inside the web giant’s data center G-scale networks to show SDN and Openflow in action. Google is using OpenFlow on custom-designed hardware for all the internal networks it runs connecting its global data centers. In a keynote address on the first day of the conference, Urs Hoelzle, Senior Vice President at Google, described how Google used OpenFlow as part of a major overhaul of its internal networking infrastructure to reduce costs and increase efficiency. This internal “G-scale” network connecting Google’s vast data centers worldwide actually carries more traffic than its external “I-scale” customer-facing network. Many in the industry pointed to Google’s announcement as a key proof point for SDN and OpenFlow as a technology that can be deployed in production environments and one that delivers quantifiable business benefits. The view was further reinforced by many of the case studies shown at the conference in the Telco/Carrier, Healthcare, Educational industries. The only online copy of the Google SDN and OpenFlow presentation that is available can be found here: ripe64.ripe.net/archives/video/884/

So what does the future hold for SDN and OpenFlow?

While we are still in the early stages and the coexistence of regular and SDN-based networks is today's norm, the growing support for SDN and OpenFLow suggests that the standard has turned a corner toward large-scale deployments. SDN and network virtualization deployment are here today and one thing is for sure, the industry is about to change in quite a dramatic way.