http://i3xi5qxvbrngh3g6o7czwjfxwjzigook7zxzjmgwg5b7xnjcn5hzciad.onion/proposals/130-v2-conn-protocol.html
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* It is not allowed to negotiate V1 connections once the v2 protocol
has been used. If this happens, Tor instances should close the
connection.
3. The rest of the " v2 " protocol
Once a v2 protocol has been negotiated, NETINFO cells are exchanged
as in proposal 105, and communications begin as per tor-spec.txt.