Software Defined Networks

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Abstract

Software defined networking is a new concept that redefined the current network device architecture and the way they behave. Due to the exponential growth of the Internet and services attached to this worldwide infrastructure, a number of issues have cropped up in modern day networks. This paper discusses a few of these limitations and how the software defined networking approach tries to alleviate them. OpenFlow, released in the year 2008, is a commercially viable implementation of this concept that is being well received by the networking industry at large. The paper also discusses the OpenFlow protocol, its implementation and the challenges facing its widespread acceptance

1. Introduction
Evolution of computer networks has traditionally been much slower than other fields of computer engineering. The primary reason for this trend has been the vertical integration of current network equipment. Almost all of today’s routers, switches and other network equipment consists of a fast switching hardware controlled by an operating system and applications built on top of it. Most network equipment vendors have their own proprietary operating system and implementation of various processes like Open Shortest Path First (OSFP), DHCP Snooping, etc and other router management functions. This vendor lock-in stifles innovation, as any implementations of new algorithms have to be approved by the vendors before it can be implemented on a commercial scale. Further, the current processes for standardization of any new protocols are glacial at best. The candidate protocols have to be approved by a numerous standards organizations and manufacturers before they are accepted as a standard. This could take any where up to ten years or more, by which time the technology would have changed dramatically. This situation can be seen in the facts like TCP/IP and other Internet protocols have not changed since its inception and even though IPv6 was standardized in 1996 it has not yet been fully implemented. However, today, there is a lot of research going on in bringing the software part out of the equipment boxes and into a remote machine. The impetus is on making this remote controller interfaces open so that users are able to apply their own logic for various network functions. This innovation in networking is popularly known as Software Defined Networking (SDN), and OpenFlow, an implementation of the SDN concept, promises much more control and flexibility with current network equipment and architecture than was possible so far. 2. Drawbacks of Current Network Technologies

The Internet, as we know today, has been a tremendous success. It began as ARPANET, a US Department of Defense internal network; but soon grew to become a worldwide infrastructure. This success of internetworking can be attributed to the fact that all the underlying protocols, like TCP, UDP, FTP etc. that ran over IP, were specified with the lowest common denominator and the network guaranteed only a best effort packet delivery system. The hosts, or all the arbitrary applications, that were built on top of this network could incorporate their own logic for ensuring reliability and security. This architecture bolstered innovation in the upper layer applications and gave rise to systems like the world-wide-web, VoIP, social networks, P2P etc. As opposed to the open interfaces of the Internet protocols, the underlying hardware, and network equipment present a very different picture. Vendors provide most of the devices that powers today’s networks as closed boxes. These devices have vendor-specific interfaces, and the control software is hard-coded onto the hardware. The protocols that define this control logic are usually over-specified, and has a long drawn standardization process. This means that vendors control the code that goes into these devices and few people can innovate, which entails long delays to introduce any new features. This...
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