SND/OpenFlowの基礎技術や最新動向をQ&A形式で解説していく本稿ではOpenFlowの技術に迫る。OpenFlowの生い立ちや標準化の流れ、業界へのインパクトも合わせて理解しておこう
What is the SDN flag "Openflow"?
OpenFlow is a network control technology proposed by the OpenFlow Switch Consorting, which is centered on Stanford University, and is now standardizing ONF (Open Networking Foundation).The ONF is located by cloud operators and network vendors such as Google and Facebook, and has a great influence.
Version 1 in 2009.The specifications of 0 have been formulated, and many products that claim OpenFlow compatible are this 1.It is based on 0.After that, the standardization in ONF is performed at a considerable speed, and the latest version is 1.3.It supports technologies such as MPLS, IPv6, and PBB (PROVIDER BACKBONE BRIDGE).In the future, this 1.It is expected that the product will proceed with 3 as a stable version.
What are the technical features of OpenFlow?
The biggest feature of OpenFlow is that route control and packet transfer are separated.In the conventional network, both are installed together, looking at the header of the input packet, the switch is determined by the transfer destination and transferred to the next switch.In these transfer methods, each network device has a characteristic that it can communicate autonomously.Distributing route control is the basic concept of TCP/IP network that realizes highly inconsistent networks, but does not provide flexible route control over the entire network.In addition, there is a hassle of setting the setting for each network device.
Differences between conventional IP networks and OpenFlow architectures (excerpt from NTT Communications materials)
On the other hand, in OpenFlow, the dedicated controller controls the route, and it is a centralized architecture in which the packet transfer on the switch side is centrally controlled.The OpenFlow controller, which controls the route, changes the route to optimize the route in a flow units so that the load is not concentrated, or change the route to recover the communication as soon as possible.For this reason, in addition to existing Mac/IP addresses, a "flo table" based on various control information, such as physical ports and layer 4 protocols, is created, and this is proposed to a switch.
In addition to the control information, the flo table also includes actions and statistical information for flow, and the OpenFlow protocol uses the controller to control the OpenFlow compatible switch.OpenFlow is the movement of transferring the input packet according to this flo table.
What is OpenFlow's flow control?
Conventional network devices were transferred to the layer structure.Each device was transferred based on the MAC address of L2 for the switch, the IP address for the router, and the Port number of the TCP/UDP for the firewall.On the other hand, in the flow control used in OpenFlow, the traffic is identified by the address and identifier of each layer, and the specified action is performed.Actions include unicasts, multicasts, bandwidth control, disposal, load distribution, recovery of disability, and transfer control of virtual ports.
Flow table used in OpenFlow (excerpt from NEC materials)
In OpenFlow, controllers and switches are built a secure channel and exchanged information such as switch ports and functions.After that, if a new flow is recognized on the switch side, the packet will be transferred to the controller, the flootable will be updated, and the transfer control will be implemented.
(Next page, what is the difference between overlay and hop -by hop?)
