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1、OpenFlowEnabling Innovation in Your NetworkNetworks have become part of the critical infrastructure of our businesses, homes and schools. This success has been both a blessing and a curse for networking researchers; their work is more relevant, but their chance of making an impact is more remote. Th
2、e reduction in real-world impact of any given network innovation is because the enormous installed base of equipment and protocols, and the reluctance to experiment with production traffic, which have created an exceedingly high barrier to entry for new ideas. Today, there is almost no practical way
3、 to experiment with new network protocols (e.g., new routing protocols, or alternatives to IP)in sufficiently realistic settings (e.g., at scale carrying real traffic) to gain the confidence needed for their widespread deployment. The result is that most new ideas from the networking research commun
4、ity go untried and untested; hence the commonly held belief that the network infrastructure has“ossified”.Having recognized the problem, the networking community is hard at work developing programmable networks,such as GENI 1 a proposed nationwide research facility for experimenting with new network
5、 architectures and distributed systems. These programmable networks call for programmable switches and routers that (using virtualization) canprocess packets for multiple isolated experimental networks simultaneously. For example, in GENI it is envisaged that a researcher will be allocated a slice o
6、f resources across the whole network, consisting of a portion of network links, packet processing elements (e.g. routers)and end-hosts; researchers program their slices to behave as they wish. A slice could extend across the backbone, into access networks, into college campuses, industrial research
7、labs, and include wiring closets, wireless networks, and sensor networks.Scope of Open Flow Switch SpecificationOpenFlow SwitchOpenFlow SwitchControllerThe basic idea is simple: we exploit the fact that most modernEthernet switches and routers contain flow-tables(typically built from TCAMs） that run
8、 at line-rate to implement firewalls, NAT, QoS, and to collect statistics. While each vendors flow-table is different, weve identified an interesting common set of functions that run in many switches and routers. OpenFlow exploits this common set of functions.OpenFlow provides an open protocol to pr
9、ogram the flowtable in different switches and routers. A network administrator can partition traffic into production and research flows. Researchers can control their own flows - by choosing the routes their packets follow and the processing they receive. In this way, researchers can try new routing
10、 protocols, security models, addressing schemes, and even alternatives to IP. On the same network, the production traffic is isolated and processed in the same way as today.The datapath of an OpenFlow Switch consists of a Flow Table, and an action associated with each flow entry. The set of actions
11、supported by an OpenFlow Switch is extensible, but below we describe a minimum requirement for all switches. For high-performance and low-cost the datapath must have a carefully prescribed degree of flexibility.This means forgoing the ability to specify arbitrary handling of each packet and seeking a more limited, but still useful, range of actions. Therefore, later in the paper, define a basic required set of actions for all OpenFlow switches.（节选）
