OpenFlow Switch
Consists of one or more flow tables, group table and meter table.A single switch can be managed by one or more controllers.
The flow tables and group table are used during the lookup or forwarding phase in order to forward the packet to appropriate port.
Meter table is used to perform simple QOS operations like rate-limiting to complex QOS operations like DiffServ etc
Need for SDN
Network Virtualization (Data Center & Cloud)– Use network resource without worrying about where it is physically located, how much it is, how it is organized, etc.
Orchestration (Cloud) - Automated arrangement, coordination, and management of complex computer systems, middleware, and services.
Programmable (Enterprise) - Should be able to change behavior on the fly.
Dynamic Scaling (Cloud) - Should be able to change size, quantity
Automation - To lower OpEx minimize manual involvement
SDN is an architecture of which OpenFlow is just a part and Clear Separation of control and data plane functionalities.
Treditional Scenario
SDN-OpenFlow Scenario
OpenFlow pipeline contains multiple flow tables starting with Table number 0
Each flow table contains one or more flow entries
Matching starts with the first flow table
If a Match is found
- Instructions associated with flow entry are executed
- Instruction may direct the packet to next flow table in pipeline
- When processing stops, the associated action set is applied and packet forwarded.
Instructions describe packet forwarding, packet modification, group table processing and pipeline processing.
Controller
Provides a network wide abstraction for the applications on one side and uses the OpenFlow protocol to communicate with a OpenFlow aware switchFlow Table
Consists of a Flow entry and an action associated with each flow entry to tell the switch how to process the flow.
Secure Channel.
Connects the switch to the controller, allowing commands and packets to be sent between a controller and the switch through OpenFlow protocol
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