Encrypted link to link idea for switch and USG

PeterUK

Been thinking about this idea due to someone wanting it and how it could work at high performance.
https://community.zyxel.com/en/discussion/comment/81105/#Comment_81105

My first idea was each end has the same encrypted and decrypted key and each packet would be encrypted like everything because this is link to link you just send the packet out but then I realized this would not work the part about sending the encrypted packet out would work but then how would you know what to decrypted at what packet length? So one way to solve this at the cost of bandwidth is the switch and USG before sending encrypted packets out is when the link is established both ends send a in the clear ACK then when each end is ready before sending encrypted packets the switch and USG link puts a in the clear packet saying the length of the next encrypted packet for each packet so that each end will know what to decrypt.