Head-of-line blocking

Head-of-line blocking is like waiting in line at the amusement park. You know how sometimes you have to stand in line for a long time before you can go on the ride, even if there are other rides that are available that you could go on right away? That's kind of like head-of-line blocking.

In computer networks, it refers to what happens when a lot of data is trying to get through a network at the same time, and it all has to go through one particular part of the network first. The other data that's trying to get through may have to wait in line until the first bit of data has been processed.

Just like waiting in line at the amusement park, this can lead to delays. If the first bit of data is taking a long time to process, all the other data that's waiting in line will also take a long time to get through, even if it could have been processed faster somewhere else in the network. So head-of-line blocking can slow down the entire network, just like a slow line at the amusement park can slow down your day.