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The canonical UDT implementation does not come with encryption, however there are some older open source GitHub repos that have attempted to add TLS to UDT. The original author of UDT, Yunhong Gu, has a project called Sector/Sphere that adds some application-level encryption to file transfer if you want to check it out: http://sector.sourceforge.net/. We've added encryption for our algorithm though!

With respect to QUIC, I believe it was designed specifically to reduce the latency of HTTP connections by using multiple UDP flows and building the reliability/ordering guarantees at the application layer.

The problem with getting performance increases out of multiple, distinct traffic flows is that you become more and more unfair to other packet traffic as you increase the number of flows you are using. For example, if you use 9 TCP (or any other AIMD) flows to send a file over some link, and a tenth connection is started, you now are taking up to 90% of the available bandwidth (because AIMD flows are designed to be fair amongst themselves).

> The problem with getting performance increases out of multiple, distinct traffic flows

Is this in response to Quic or just multiple TCP streams? Afaik quic multiplexes everything over a single connection on a single port.

As for fairness, the reality (aiui) is that neither tcp nor udp is guaranteed more bandwidth. It's all up to middleboxes, and I think there are quite a few that assume udp is "less important"/"can deal better with degraded performance" (eg video conferencing, live streams) and instead prefers tcp, in which case there's no recourse. Did you ever observe any conditions like this?

> AIMD

Additive Increase Multiplactive Decrease (for others wondering)

> a feedback control algorithm best known for its use in TCP congestion control. AIMD combines linear growth of the congestion window when there is no congestion with an exponential reduction when congestion is detected.

-- https://en.wikipedia.org/wiki/Additive_increase/multiplicati...