Call flow document for OpenVPN

[M0hanrajp]

Below is an example of OpenConnect protocol connection flow between client and server from https://www.ietf.org/archive/id/draft-mavrogiannopoulos-openconnect-04.html

Question: Is there a similar picture/connection process call flow diagram for "OpenVPN" ?

OpenConnect call flow:

Based on my understanding following is the flow for OpenVPN.

• TCP handshake between client and server.
• TLS handshake between client and server.
• send configuration to the server.
• establishment of tunnel (TCP / UDP based on the configuration provided

Is my understanding proper ? I would like to confirm about it and get if there are any reference call flow available.

OpenVPN connection process I have assumed it from the following source:

• https://en.wikipedia.org/wiki/OpenVPN
• https://wiki.wireshark.org/OpenVPN
• https://www.junmajinlong.com/files/Mastering_OpenVPN.pdf (page 22 - 28)

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Thanks

[schwabe]

Not in a diagram per se like that but the protocol is described in https://openvpn.github.io/openvpn-rfc/openvpn-wire-protocol.html

But your understanding of the OpenVPN flow seems to be flawed. There is only one TCP/UDP connection per conection that will be used for everything with OpenVPN's own framing to distinguish between message types. Your flow assumpe at least two connections.

[M0hanrajp]

@schwabe, Thanks for that reference material, It's something that I was looking for !

Based on your reply

"Your flow assumpe at least two connections."

I did not assume two connections, when you are establishing the tunnel control + data both either on TCP or UDP (this is correct right) ?

[schwabe]

@M0hanrajp please read the linked document if you want to know the protocol.