Why the router buffer size is so important
Do you know how much benefit a router with a slightly larger buffer can bring? A little smaller, you know how much sadness it would bring?
When running at high speed, sometimes two cars collide slightly, which will bring dozens of kilometers of congestion... This is a local accident triggering a global chain reaction. The year before last, the Shanghai-Jiaxing Expressway construction, demolition of the central green belt, cancellation of hard shoulder, two lanes into three lanes, you can not underestimate this lane, the effect is great.
For the network, when the data packet is on the network cable, it is absolutely safe and absolutely full speed forward. The most dangerous thing is to reach the forwarding device. The inherent delay caused by the device processing the data packet must have a chance to be buffered. The processing acceleration ratio must correspond to the buffer size. At this time, increasing the buffer size is similar to adding lanes to the highway. The effect is great. No matter how much, there's a formula between buffer size and line bandwidth, and frankly TCP helps a lot with that formula.
We know that UDP has no state and no connection. If it is lost, it will be lost. No one knows. Everything is silent. So the forwarding device can't measure how big the buffer is. TCP can help. TCP has an RTT, that is, the time required for a packet to go back and forth. After opening the timestamp, this measurement is very accurate, so the buffer size setting of the forwarding device is related to this. That is, the buffer must be able to hold a TCP round-trip packet that lasts for how long? This is determined by bandwidth. If the buffer size is less than this value, TCP will continue to drop packets once internal queue congestion or delay occurs. Therefore, the higher the speed of the link, the larger the buffer size, network bandwidth continues to increase today, how to buffer such a large amount of data per unit time, is a big problem. TCP slows down when it detects packet loss, but what about UDP?
Ultimately, the deciding factor in the buffer size of a forwarding device is memory access efficiency, and what kind of storage devices are available today to meet this requirement? The amount of data is huge, and the expensive things are directly passed. What is a divine weapon without considering parallelism?
It's late at night! Xiao Xiao's birthday has passed. I had a good time. I'm happy too!
