Performance comparison between traditional network architecture switches and sdn network architecture switches—Vecloud

The management of network equipment has always been an important topic, but today's SDN network separates the control layer from the data layer of the network equipment and centrally manages it by an external controller. The network equipment only performs packet transfer actions, which greatly simplifies the management of many equipment. This article conducts a performance test and comparison between traditional switches and SDN switches. In terms of transmission rate, traditional switches can reach 90% of the bandwidth, while SDN switches have only 25% in TCP transmission, UDP is almost impossible to transmit, and the overall delay of SDN switches The time is about 13.23 times that of traditional switches. Due to the low
CPU frequency of the SDN switch , the packet processing speed is slow, and the packet is forwarded to the controller, which increases the extra delay time. In addition, the packet transmission rate is too fast, or the packet is too large to be divided, resulting in a large number of packets being re- These four factors cause the performance of SDN switches to be inferior to traditional switches.
　　In today's corporate networks, cloud computing has become an indispensable part. Centralized management of scattered servers makes resources that are actually located in different places seem to be placed in the same place. In this way, not only has a lot of resources, but also can improve the system's fault tolerance, that is, resource virtualization. After discovering the benefits of virtualization, researchers also want to virtualize the network responsible for connection and transmission resources, so that the performance and management of the network can be further improved. However, in practice, it is found that the network is different from other resources. Even if the equipment is centralized, it will only achieve a centralized effect. In terms of management, each equipment must be set individually, and the effect of virtualization cannot be further achieved. . In order to solve the problem of network virtualization, the
research team led by Nick McKeown proposed to separate the control layer of the network for centralized management. The network equipment scattered everywhere is only responsible for the service of data transmission, which is the software-defined network (Software-Defined Network).
Networking, SDN) concept. In this way, path calculations, environment configuration, and equipment maintenance can all be processed centrally, achieving the goal of virtualizing the network control layer. This article will
test three items for the performance of traditional switches and SDN switches:
　　(1) Transmission rate;
　　(2) OpenFlow controls the packet generation rate;
　　(3) Delay time to understand the difference between traditional switches and SDN switches.
　　Introduction to
　　SDN SDN separates the control plane (control plane) of network equipment from the data plane (forwarding
plane), and the external controller (controller)
centrally manages the control layer, leaving only the network equipment of the data layer. Need to be responsible for processing the part of the packet delivery. In the controller, the defined network behavior is executed in the form of software. According to the different behaviors defined by the software, the underlying network devices will have different behaviors. For example, the controller defines the action of broadcasting after receiving the packet. At this time, the underlying network device is a hub; or it is defined to analyze the header after receiving the packet and transmit it to the specified port (port), then the underlying network device will become a Switch (switch). In this way, SDN
can be deployed in a variety of different network environments quickly and without the need to replace physical network equipment. More importantly, the centralized and programmatic management and control layer can save a lot of deployment time. With the maintenance of human resources, the goal of virtualization is truly achieved.
　　SDN architecture
　　In the process of SDN development, many researchers have proposed various methods of SDN architecture. Among them, OpenFlow is the most famous. The following will take OpenFlow as an example to introduce
the architecture of SDN network, and focus on switches as network equipment. Discussion and comparison.
　　OpenFlow is proposed by a research team led by Nick McKeown. The purpose is to provide an open communication protocol (protocol)
so that the program can control the flow table on different switches to achieve the effect of SDN. There are three main parts:
　　(1) Flow chart: Write the flow direction of the packet in the switch, and transmit the packet according to the flow direction defined in the flow chart after the packet enters the switch.
　　(2) Controller: The packet whose flow direction is not defined in the process table will enter the controller, and the controller determines the next flow direction of the packet.
　　(3) OpenFlow communication protocol: through the SSL encrypted channel, the switch and the controller can communicate.
　　Comparison with traditional switch architecture
　　In today's network environment, the switch itself has many functions. In this article, we call it a traditional switch. Here we compare it with
the architecture of SDN switches, as shown in Figure 1. The left half of Figure 1 is the architecture of the traditional network, and the right half is
the architecture of the SDN network. From the traditional network architecture, it can be seen that the switch integrates all functions, from the lowest layer of packet transmission, middle-level network management, to the uppermost application programs are all handled by a switch. The advantage is that it can be designed by hardware. To achieve the behavior of the switch and increase the processing speed of the switch; but the disadvantage is that the same function appears on multiple switches. When the behavior of the switch needs to be changed, it must be set for each switch one by one. In the worst case, it needs to be changed. When the behavior has been written into the hardware, the entire switch must be directly replaced to complete the setting, which will waste a lot of costs.
　　The SDN
network architecture is different from the traditional network. The bottom layer is only responsible for packet transmission. The functions located in the middle and upper layers of the traditional network are transferred to the controller and controlled by the software in the controller. The biggest advantage is that it can be fast and does not need to be replaced. Switch, deploy a variety of different network environments, and save a lot of deployment time and maintenance human resources, to achieve the effect of virtualization.
　　OpenFlow switch introduction
　　The OpenFlow switch is a programmable switch, which mainly runs two programs of protocol and ofdatapath on the switch and records a flow chart. The function of ofprotocol is to record the information of packets entering and leaving the switch, the function of ofdatapath is to process the packets entering the switch, and the function of the flow table is to record rules and processing actions. When a packet enters the switch from the external network, ofprotocol will first know which port the packet entered into the switch, record it in the packet, and then hand it over to ofdatapath for processing.
　　The OpenFlow switch mainly transmits packets. It can only determine the types of control and data packets and perform a few simple actions defined on the flow chart. The rest will be sent to the controller for decision because of the undefined flow chart. The effect of layer and data layer separation.
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