Comment by LukeShu
No? The "transport" layer is layer 4 in the 7-layer OSI model (physical/datalink/network/transport/session/presentation/application) and 5-layer IP model (physical/network/internetwork/transport/application). That is: the "transport" provides reliable continuous data-stream abstraction over the lower-layers' discreet and unreliable packets; e.g. TCP.
And that data-stream the interface that TLS provides; to the higher layers it looks like a transport layer.
I was about to agree with you, and then I read the article on DTLS.
> And that data-stream the interface that TLS provides
That’s exactly the problem. You might lose a UDP packet. That would corrupt data encrypted with stream cipher.
With DTLS, each packet is encrypted individually.
https://en.m.wikipedia.org/wiki/Datagram_Transport_Layer_Sec...