Software-defined networking

Software-defined networking (SDN) is an approach to computer networking that allows network administrators to manage network services through abstraction of higher-level functionality. This is done by decoupling the system that makes decisions about where traffic is sent (the control plane) from the underlying systems that forward traffic to the selected destination (the data plane).

SDN requires some method for the control plane to communicate with the data plane. One such mechanism, OpenFlow, is often misunderstood to be equivalent to SDN, but other mechanisms could also fit into the concept.

History

The origins of software-defined networking (SDN) began shortly after Sun Microsystems released Java in 1995.

One of the first and most notable SDN projects was AT&T's GeoPlex.AT&T Labs Geoplex project members Michah Lerner, George Vanecek, Nino Vidovic, and Dado Vrsalovic leveraged the network APIs and dynamic aspects of the Java language as a means to implement middleware networks. "GeoPlex is not an operating system, nor does it attempt to compete with one. It is networking middleware that uses one or more operating systems running on computers connected to the Internet. GeoPlex is a service platform that manages networks and on-line services. GeoPlex maps all of the IP network activities into one or more services."

SDN

SDN can stand for:

Forwarding plane

In routing, the forwarding plane, sometimes called the data plane, defines the part of the router architecture that decides what to do with packets arriving on an inbound interface. Most commonly, it refers to a table in which the router looks up the destination address of the incoming packet and retrieves the information necessary to determine the path from the receiving element, through the internal forwarding fabric of the router, and to the proper outgoing interface(s). The IP Multimedia Subsystem architecture uses the term transport plane to describe a function roughly equivalent to the routing control plane.

In certain cases the table may specify that a packet is to be discarded. In such cases, the router may return an ICMP "destination unreachable" or other appropriate code. Some security policies, however, dictate that the router should drop the packet silently, in order that a potential attacker does not become aware that a target is being protected.

The incoming forwarding element will also decrement the time-to-live (TTL) field of the packet, and, if the new value is zero, discard the packet. While the Internet Protocol (IP) specification indicates that an Internet Control Message Protocol (ICMP) time exceeded message should be sent to the originator of the packet (i.e. the node indicated by the source address), the router may be configured to drop the packet silently (again according to security policies).

Network function virtualization

In computer science, network function virtualization (NFV) is a network architecture concept that uses the technologies of IT virtualization to virtualize entire classes of network node functions into building blocks that may connect, or chain together, to create communication services.

NFV relies upon, but differs from, traditional server-virtualization techniques, such as those used in enterprise IT. A virtualized network function, or VNF, may consist of one or more virtual machines running different software and processes, on top of standard high-volume servers, switches and storage, or even cloud computing infrastructure, instead of having custom hardware appliances for each network function.

For example, a virtual session border controller could be deployed to protect a network without the typical cost and complexity of obtaining and installing physical units. Other examples of NFV include virtualized load balancers, firewalls, intrusion detection devices and WAN accelerators.

60 Seconds

60seconds is a news programme which runs between shows on BBC Three. It broadcasts under the BBC News format and branding. The main presenter is Sam Naz. Previous presenters include Tasmin Lucia-Khan, Andy May, Matt Cooke, James Dagwell and Claudia-Liza Armah.

Format

The programme lasts for 60 seconds as the name suggests, during which time the presenter condenses some of the day's news, sport and entertainment stories into a 60-second bulletin. It only runs from 7pm–12:15am with a bulletin at the top of the hour or after a programme has ended, if more than an hour. Throughout the bulletin, a line gradually crosses the screen which effectively counts down the seconds. There are two sets of pictures running simultaneously for each story. Five stories are featured in every bulletin. 60 Seconds is presented in a style in keeping with the channel. Humour is a feature and some of the scripting often raises a smile. During the 2012 Summer Olympics and 2014 commonwealth games bulletins ran from 7am–12:15am with a round-up of the day's other news stories.