* Michael Mol <mike...@gmail.com> [120210 12:51]: [..] > That's what I was talking about. Where I work, we use OpenVPN, > operating in UDP mode. This is after several bad experiences using it > in TCP mode. > > By "UDP mode" and "TCP mode", I mean OpenVPN's connections to other > OpenVPN nodes were in UDP or TCP, respectively. When OpenVPN's > connections operate over TCP (and thus it gets guarantee'd delivery), > you can create a situation where a tunneled TCP connection attempts to > push data faster than your Internet connection can allow because it > never gets any congestion feedback; OpenVPN was accepting packets > faster than it could shove them through, and was buffering the rest.
So obviously OpenVPN wasn't handling congestion appropriately and should have been using some queueing discipline to discard instead of letting transmit queues grow unbounded. But switching to UDP from TCP just pushes the problem off your OpenVPN gateway and onto the "outside" network. If you're really receiving more traffic than can be sent over the "outside" network, now you're relying on intermediate routers to "do the right thing" with your excess UDP traffic and most likely impacting TCP traffic through the same router. Todd
