Table of contents
2. Characteristics of SDN Architecture
1. SDN
1. Introduction of SDN
Software Defined Network
SDN is derived from a new network innovation architecture proposed by the Clean Slate research group of Stanford University in the United States. It can define and control the network through software programming. It has the characteristics of separation of control plane and forwarding plane and open programmability.
The core concept of SDN is to hope that application software can participate in the control and management of the network, meet the business needs of the upper layer, and simplify network operation and maintenance through automated service deployment.
SDN is not a specific technology, it is a network design concept, planning the various components of the network (software, hardware, forwarding plane and control plane) and the interaction between them.
2. Characteristics of SDN Architecture
① Stream-based forwarding
The packet forwarding work of the packet switch in SDN can be based on any number of header field values in the transport layer, network layer or link layer header.
Packet forwarding rules are precisely specified in the flow table of the switch, and the job of the SDN control plane is to calculate, manage and install flow table entries in all network switches.
② Separation of data plane and control plane
- The data plane consists of network switches that perform match-add operations in their flow tables
- The control plane consists of an SDN controller and several network control applications
The network control application is used to determine and manage the flow table of the switch.
③ Network control function: located outside the data plane switch
The control plane consists of an SDN controller and several network control applications.
SDN controller:
- Maintain accurate network state information
- Provide this information to network control applications
- Provides methods to network control applications
④ Programmable network
The network is programmable through network control applications running in the control plane. These applications use the API provided by the SDN controller to define and control the data plane in the network device.
3. SDN controller
① Interface layer: provide abstract API for network control applications
② Status management layer: responsible for maintaining a consistent view of the network status
- Maintain the state of links, switches, services, etc.
- By using a distributed database
③ Communication layer: Communication between the SDN controller and the controlled switching equipment
4. SDN universal forwarding
The core idea of SDN is to establish a general forwarding system
- Each switching device contains a flow table (flow table)
- The flow table is calculated and distributed by a logically centralized remote controller
Two, OpenFlow
Originated from Stanford University's Clean Slate project, it is now widely used and recognized.
It is the communication interface standard between the SDN controller and the data plane:
- Data plane that allows direct access and manipulation of network devices
- Separate the control plane and data plane, and use standard protocol communication between the two
- The data plane adopts flow-based forwarding
The composition of the OpenFlow network:
- OpenFlow network device (OpenFlow Switch)
- OpenFlow Controller (OpenFlow Controller)
- OpenFlow Channel (OpenFlow Channel)