[multipathtcp] q about off-path proxy (explicit mode)

[Yoshifumi Nishida <[e-mail]>]

Hello,
Now, I am trying to understand off-path (explicit mode) scenarios.
In explicit mode, we need to tell the final destination to the proxy
through MP_Convert Information Element. But, this requires mptcp
connections. In order to clarify which cases can use this mode, I have
drawn the following 7 cases.
I am wondering if we can support case 3) 4) 5) with explicit mode or not.
Also, supporting case 6), 7) seems to be a bit unclear.
It would be great if some folks could clarify this.

------------------------------------------------------------
-----------------


     C ... client,   S ... Server,  P ... Proxy,  MCIE ... MP_Convert
Information Element
   ====   ... mptcp connection
   ----   ... tcp connection


single proxy cases

1)   C ========== P -------- S         : C tells S's addr to P by MCIE
2)   C ========== P ======== S         : C tells S's addr to P by MCIE
3)   C ---------- P ======== S         : How C tell S's address to P?

double proxy cases

4)   C -------- P1 ======== P2 ------- S  : How C tell S's address to P1?
5)   C -------- P1 ======== P2 ======= S  : How C tell S's address to P1?
6)   C ======== P1 ======== P2 ------- S  : C tells S's addr to P1 by MCIE
and P1 forwards it to P2?
7)   C ======== P1 ======== P2 ======= S  : C tells S's addr to P1 by MCIE
and P1 forwards it to P2?