Has Dropbox ever experimented with SCTP or other protocols that don't enforce strict ordering of packets? I know some middleboxes struggle with SCTP (they expect TCP or UDP), but in that case you do SCTP over UDP or have a fall back.
Sadly, middleboxes are a real problem, esp. with our Enterprise customers. We had this problem even with HTTP/2 rollout so there is even a special HTTP/1.1-only mode in the Desktop Client for environments where h2 is disabled.
In the future we are planing on having an HTTP/3 support which will give us pretty much the same benefits as SCTP with a better middlebox compatibility.
