The draft-ietf-quic-datagram has the following words: DATAGRAM frames belong to a QUIC connection as a whole, and are not strongly associated with any stream ID at the QUIC layer.
Can DATAGRAM belong to stream? And one stream has two type: one for unreliable transmission(DATAGRAM FRAME) and another one for reliable transmission(STREAM FRAME).
At the QUIC layer, datagrams don't belong to streams. In HTTP/3 however, datagrams are associated with streams - see draft-ietf-masque-h3-datagram for details.
The draft-ietf-quic-datagram has the following words: DATAGRAM frames belong to a QUIC connection as a whole, and are not strongly associated with any stream ID at the QUIC layer. Can DATAGRAM belong to stream? And one stream has two type: one for unreliable transmission(DATAGRAM FRAME) and another one for reliable transmission(STREAM FRAME).