The nice thing about SFTP is that the SSH setup actions are identical,
regardless of which application is used.
No need for us to revisit every step,
but we see the initial TCP session form first,
using port 22.
Then, the key exchange INIT messages are sent,
beginning the session parameter negotiation.
Diffie Hellman then runs,
transferring the server's public key to the client and
generating the unique session key.
Not much to see here folks.
This is the encrypted file transfer and its associated signaling in progress.
Only one TCP session is used,
and all of the SFTP signaling and data are transferred within it.
Other than the IPv6 addressing from a packet on the wire perspective,
it looks identical to IPv4 SFTP.
This layer 4 behavior simplifies security across firewalls in the network. All of the data is still encrypted, only using IPv6 as the layer 3 protocol now.