A media request in NeoLoad has specific parameters that you can configure like buffer length and video bitrate.
The first time your video is played, NeoLoad will fill your buffer up to 5s. Then, it will start playing the video. In the meantime, the video will still be downloading.
Then, you may have three different behaviors:
1. The download and the video bitrate is equal. Your buffer will still be around 5s and you should not have any lag to play your video
2. The download is faster than your video bitrate. Your buffer will continue to increase (slowly) and it can be much higher than your 5s buffer. You should not see any lag to play your video
3. The download is slower than your video bitrate. Your buffer will decrease until around 0, you will start to see some lags i.e video playing is stopped until the buffer is filled up to 5s. Then, NeoLoad will start playing the video again.
To sum up, the buffer configured in your media request is a minimum value and so it can be reached in some circumstances.
For more information, see “Media requests” under “Design” section in NeoLoad documentation.