Simple understanding of CDN, SDN and QoS

CDN、SDN、QOS Simple understanding

- CDN

• CDN：CDN The full name is Content Delivery Network, The content distribution network . simply , Just like JD's local warehouse ; Jd.com will follow certain strategies , Deliver the goods to the warehouse at the place where the order may be issued in advance . For example, when Beijing purchases self operated goods , Deliver directly from Jingcang , Soon .
• CDN It is an intelligent virtual network based on the existing network , Rely on edge servers deployed everywhere , Load balancing through the central platform 、 content distribution 、 Scheduling and other functional modules , Let users get the content they need nearby , Reduce network congestion , Improve user access response speed and hit rate .
• CDN The basic principle is to widely use various cache servers , Distribute these cache servers to areas or networks with relatively centralized user access , When users visit the website , Use the global load technology to point the user's access to the nearest working cache server , The cache server responds directly to user requests .
• CDN The basic idea is to avoid the bottlenecks and links on the Internet that may affect the speed and stability of data transmission , Make content transfer faster 、 A more stable . A layer of intelligent virtual network based on the existing Internet, which is composed of node servers placed everywhere in the network ,CDN The system can connect each node according to the network traffic in real time 、 Comprehensive information such as load status, distance to the user and response time redirect the user's request to the nearest service node . Its purpose is to enable users to get the required content nearby , solve Internet The state of network congestion , Improve the response speed of users to visit the website .

- SDN：

• SDN： Software Defined Network （Software Defined Network,SDN） Is a way to realize network virtualization . Its core technology OpenFlow By separating the control surface and data surface of network equipment , Thus, the flexible control of network traffic is realized , Make the network more intelligent as a pipeline , It provides a good platform for innovation of core network and application .
• Using the idea of layering ,SDN Separate data from control . At the control level , Including a logic centric and programmable controller , Master the global network information , It is convenient for operators and researchers to manage and configure networks and deploy new protocols . In the data layer , Only provide simple data forwarding function , Can quickly process matching packets , Adapt to the increasing demand of traffic . Open unified interface is adopted between the two layers （ Such as OpenFlow etc. ） Interact . The controller sends unified standard rules to the switch through the standard interface , The switch only needs to perform the corresponding actions according to these rules .
• Router and switch are in SDN The infrastructure layer in .

- QOS：

• QoS（Quality of Service, Service quality ） It means that a network can utilize various basic technologies , Provide better service capability for specified network communication , It's a kind of network security mechanism , It's a technology to solve the problems of network delay and blocking .QoS It's very important for a network with limited capacity , Especially for streaming multimedia applications , for example VoIP and IPTV etc. , Because these applications often need a fixed transmission rate , It is also sensitive to delay .CDN It is an idea of improving service quality .