-> Software-defined networking (SDN) decouples the data and control planes and implements the control plane in software instead, which enables a network administrator can shape traffic from a centralized control without having to touch individual switches.
-> The administrator can change any network switch’s rules when necessary — prioritizing, de-prioritizing or even blocking specific types of packets.
-> In SDN, a centralized controller has a complete end-to-end view of the entire network, and knowledge of all network paths and device capabilities resides in N/w.
-> So the controller serves as a single point of configuration for the entire network.
-> The internal architecture of a network device has three planes of operation:
i. Management plane:
-> The management plane handles external user interaction and administrative tasks like authentication, logging, and configuration via a Web interface or CLI.
-> User interface – SSH, HTTP, API.
ii. Control plane:
-> The control plane administers the internal device operations, providing the instructions to direct the packets;
-> it also runs the routing and switching protocols and feeds operational data back to the management plane.
-> CPU, Memory, OS, STP, OSPF, BGP.
-> Control plane on each network device communicates with the control planes on all other devices in the network using protocols like OSPF or Spanning Tree.
-> So all system elements in an network must be coherent for the network to function as a whole.
iii. Data(Forwarding/user) plane:
-> The data plane is the engine room that moves packets through the device, using the forwarding table supplied by the control plane to determine the
output port.
-> In conventional networking, all three planes are implemented in the firmware of routers and switches.
OpenFlow:
-> OpenFlow is a protocol that allows a controller to tell network switches where to send packets.
-> In a conventional network, each switch has proprietary software that tells it what to do. With OpenFlow, the packet-moving decisions are centralized.
-> In a conventional switch, packet forwarding (the data path) and high-level routing (the control path) occur on the same device.
-> An OpenFlow switch separates the data path from the control path. The data path portion resides on the switch itself; a separate controller makes high-level routing decisions. The switch and controller communicate by means of the OpenFlow protocol. This methodology, known as software-defined networking (SDN).
SDN Architech
Mininet:
-> Mininet is a network emulator. It runs a collection of end-hosts, switches, routers, and links on a single Linux kernel. It uses lightweight virtualization to make a single system look like a complete network, running the same kernel, system, and user code.
-> Mininet enables to quickly create, interact with, customize and share a software defined network prototype, and provides a smooth path to running on hardware.
Sample Virtual Network – Mininet
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