As one approach of the network agility and mobility lifting/increasing, Software Defined Networking (SDN) uses canned processes to provision the network. It is an emerging technology designed to address mobility and agility. An OpenFlow switch is a software program or hardware device that forwards packets in a SDN environment. With the popularity of SDN network, a lot of people puzzle about if it is necessary to use SDN network switch for SDN network. This article would give a brief introduction to SDN network and SDN switches, and provide a satisfied answer about the necessity of SDN switch for SDN network.
In a software defined networking system, canned processes are used to provision the network. For instance, users should be able to program the network when they want to build a tap, instead of building a network tap using an appliance. SDN makes the network programmable by separating the control plane (telling the network what goes where) from the data plane (sending packets to specific destinations). It relies on switches that can be programmed through an SDN controller using an industry standard control protocol, such as OpenFlow.
A OpenFlow/SDN switch, when it receives a packet, that it does not have a flow for (Match + exit port) will contact a SDN controller(Server) and ask what must it do with this packet. The controller can then download a flow to the switch, possibly including some packet manipulation. Once the flow is downloaded to the switch it will switch similar packets at wire-speed
Having a central server that knows the network layout and can make all the switching decisions and build the paths gives us new capabilities. The advantages of the SDN switches are listed in the below:
1.The SDN controller could route non critical/bulk traffic on longer routes that are not fully utilized.
2.The SDN controller could send the initial couple of packets to a firewall, and once the firewall is happy/accepts the flow, the SDN controller can bypass the firewall thus removing load from the FW and allowing multi-gigabit datacenters to be fire-walled.
3.The SDN controller can easily implement load-balancing also at high data rates by just directing different flows to different hosts, only doing the set-up of the initial flow’s.
4.Traffic can be isolated without the need for vlan’s, the SDN controller can just refuse certain connections.
5.Setup a network TAP/Sniffer easily for any port or even specific traffic by programming the network to send a duplicate stream to a network monitoring device.
6.It allows for the development of new services and ideas all in software on the SDN controller. OpenFlow-Actions.
SDN Switch Vs. Non-SDN switch
SDN switches are specially produced for SDN networking. A normal switch works independently of the rest of the network.
In a traditional optical switch device, packet forwarding and high-level routing are on the same device. An OpenFlow switch separates the data path from the control path. Separate controller makes high-level routing decisions. The switch and controller communicate by the OpenFlow protocol.
In the old switches you would have to go to the locations of the switch login to the command line and then configure it through the command line. With open flow enabled switches you could program the switch by sending commands through openflow messages. SDN controller helps you to program the switches. In other words, SDN controller uses openflow and gives you an interface to program the switched.
Special SDN data switches are not required to implement software-defined networks. SDN architectures will take many different approaches as they mature and change, and each technology vendor will have a unique take on how to implement SDN. For example, VMware, with its acquisition of Nicira, will implement SDN protocols in its Switch software, which does not require specialized hardware or a controller. Many suppliers are offering specific SDN controllers, such as OpenFlow controllers offered by Big Switch, NEC, HP and IBM, and controllers that are not OpenFlow-specific and use other protocols (offered by Cisco and Juniper).