Recently, someone always ask me, why use a high defense CDN after the video is still stuck into the PPT, this problem I really do not rarely encounter. Last year, our team took over a live broadcast project, the father of the party threw over a “jamming rate must be pressed to 5% below”, the results of a check to find that they use the so-called “high-defense CDN” is simply a bare state - - nodes randomly selected, bandwidth gouging search, and even did not open TCP optimization. -The nodes are randomly selected, the bandwidth is gouged, and the TCP optimization is not even on. My blood pressure came up on the spot.
Video lag thing, eighty percent of the problem in the node scheduling and bandwidth resources. Some vendors blowing sky-high, the actual nodes assigned to you may be half a world away from the user. I tested a small factory CDN, Southeast Asian users are actually scheduled to the U.S. node, latency directly soared to 300ms +, which can not card?
First of all, node optimization. Never believe those “thousands of nodes around the world” propaganda words, the number of nodes is not as high as the quality. We tested three vendors last year: CDN5's North American node quality is stable, but the Asia-Pacific region is often pumping; CDN07's European line is excellent, but Southeast Asia is a third-party aggregation line; finally, we chose 08Host, although the total number of nodes is not much, but each node has been optimized for BGP convergence and TCP acceleration.
The key depends on the node scheduling strategy. Intelligent DNS resolution is just the foundation, real optimization has to be done:
This is my go-to node health check script:
Bandwidth protection is the main event. Many vendors play word games, claiming that “unlimited bandwidth” is actually behind the shared bandwidth pool. Peak period all customers together to grab bandwidth, can not be stuck? We have suffered this loss - a live event during the sudden lag soared, and finally found that the vendor gave us 100 megabytes of bandwidth by other customers traffic washed out.
Nowadays, vendors are definitely required to provide it before signing a contract:
The test found that 08Host in this piece to do the most real, encountered an attack to ensure a minimum of 50% of available bandwidth, while some vendors detect an attack on the direct pinch flow to you.
Optimization of the video transmission protocol is the real embodiment of the technology gap, TCP protocol directly to the video is a disaster - packet loss and retransmission mechanism in minutes to make the video card into a mosaic. It is recommended to turn on:
Don't forget the QUIC protocol support. After we forced QUIC on mobile, the lag rate dropped by 37%. Especially in weak network environments (subway/elevator), QUIC's 0-RTT connectivity advantage is a lifesaver.
High defense capabilities can actually affect smoothness. Some vendors' cleaning strategies are extremely rough, and they just drop packets when they see abnormal traffic. Last year, we encountered a cleaning device mistakenly killed video packets, resulting in the loss of key frames of the strange things. Now it will all be required of the vendor:
The real-world data speaks the loudest. Here's a comparison before and after optimization for one of our clients:
One last piece of solid advice: don't just look at the price. Once the figure of a cheap choice of a ten cents per GB vendors, the results of the high rate of lag to the party to claim. Now the team selection must test three items: node latency stability, bandwidth burst capacity, cleaning strategy fineness. 08Host although more expensive but really stable, CDN07 suitable for European business, CDN5 North American nodes can be used as a supplement.
These days, even CDNs have to “prevent teammates” - prevent unreliable vendors, prevent bandwidth-sharing neighbors, and prevent rough cleaning strategies. If you really want to reduce the lagging rate, you have to be like an old hunter staring at the prey as dead on every technical detail. The day you find that the video is not stuck, most likely not lucky, but some engineer stayed up all night to tune out.
