It is a common knowledge that transferring TCP packet inside a tunnel with TCP connection can create a devastating effect called TCP meltdown and degrade tunnel quality greatly. I somehow wondering if similar effect may happen in we try to transfer TCP data over a Quic connection. Even though Quic is UDP packets, but it need to have something similar to windowing for keeping track of received packets in order to provide a connection-oriented protocol. So I'm not sure if a similar effect will happen or not.
Any idea?
QUIC indeed uses a similar congestion control as TCP, see https://www.rfc-editor.org/rfc/rfc9002.html#name-congestion-control. So when tunnelling a TCP connection over a QUIC stream, I would say the same "meltdown" problems can occur (a QUIC stream has the same properties as a TCP connection: reliable ordered stream of byte, so the stream will stall if QUIC packets are lost).
However, a QUIC extensions is being defined for sending datagrams, https://datatracker.ietf.org/doc/html/draft-ietf-quic-datagram. That might provide a better way for transporting TCP packets, as these datagrams will never be retransmitted at QUIC level. However, it would require TCP packets to fit into a Datagram frame.