What exactly is PCDN? Is it a disruptive "black technology"?

What is PCDN?

CDN (Content Distribution Network) is a network architecture that provides fast, efficient and reliable website and Internet content distribution services through a distributed server system. It deploys multiple data centers in different geographical locations and caches content to the server closest to the user, thereby speeding up content loading and improving user access experience.

PCDN (P2P CDN) is a peer-to-peer (P2P) technology-based CDN that uses idle resources of numerous user devices distributed in different locations, such as home broadband, to store and transmit content. Compared with traditional CDN, PCDN can provide distribution efficiency comparable to CDN while reducing costs through this decentralized approach.

What are the application scenarios of PCDN?

Video on demand and live streaming: Utilizes idle bandwidth of user devices for content distribution, which is suitable for video on demand and live streaming, especially in areas with limited bandwidth resources.

Large file distribution: PCDN can be used for the distribution of large files, such as game content, software updates, etc., and is particularly suitable for cost-effective distribution scenarios.

Communities and Web Forums: In communities and web forums, PCDN can be used to distribute user-generated content, such as images and videos.

What are the characteristics of PCDN in home broadband?

Low cost: PCDN can effectively utilize idle bandwidth in home broadband and reduce dependence on expensive servers and data centers, thereby significantly reducing the cost of content distribution.

Dispersing traffic: Since PCDN is distributed among many home broadband users, it can effectively disperse access pressure and improve the system's stress resistance and reliability.

Bandwidth limitation: Since the bandwidth and stability of home broadband are relatively limited, the speed and quality of content distribution may be affected.

Security issues: In a home broadband environment, data security and privacy protection is a major challenge and requires additional security measures.

Is PCDN really a black technology?

Recently, we received complaints from some home broadband users that some resources could not be viewed when using a certain brand of TV built-in APP through mobile home broadband and the problem location was not concentrated. During the test, it was found that it could be viewed normally using mobile phone hotspots and other operator networks. After using WIFI or wired broadband network, TV users can watch live TV and various on-demand programs in the application through the built-in APP on the TV. According to user complaints, the uplink and downlink quality of BRAS and OLT equipment was checked, and no poor quality links were found. The network quality on the access side of the complaining users was checked, and the network quality on the user access side was good. Through user terminal inspection, the TV terminal models and software versions involved in the problem users were quite different, and most of them were not old TVs, so the fault was ruled out due to TV model problems. Use cellular-z to check the WIFI quality of the user-side wireless router. Most users have no co-frequency or adjacent frequency interference at home. Replacement of new routers for some users did not improve the fault phenomenon.

Through the analysis of the APP business application process, the test results in various network environments, and the comparison analysis of the captured IP packets, it can be seen that when users use the APP normally, the resource CDN node scheduled is the IDC address in the network of each operator. When the mobile home broadband users encounter abnormal lag or cannot open resources, the resource distribution node scheduled is the mobile home broadband CGN public network NAT address. This type of resource node is most likely a PCDN node, and the network quality and distribution quality cannot be effectively guaranteed, which is easy to cause perception problems. After actively contacting the TV's built-in APP company to coordinate and optimize the scheduling of this poor quality resources, the test business returned to normal.

It can be seen that video APP (TV, video, short video) resources are usually distributed using CDN scheduling. In order to ensure user perception, general content providers use data center CDN nodes with stable network quality and good server status to distribute resources. Recently, some content providers have adopted the cheap PCDN method to distribute content resources in order to reduce operating costs. This distribution method cannot effectively guarantee the quality of the network and content, and is prone to cause perception problems.