question

Now I implemented the RTSPS server through openssl,and the echo show and RTSPS server are on the same LAN,echo show will connect to my server and play RTSP video, I think the delay is very low under the local area network, but now the echo show appears 3 seconds later, and the delay is about 3s, I would like to ask what is the reason for this, how can I improve the delay?And what is the normal delay? Thanks for the answer.