UDT4 and rsync? support to socket.c?

Jamie Lokier jamie at shareable.org
Tue Mar 23 18:45:52 MDT 2010

Jan Wagner wrote:
> Hi, has anyone of the devels considered adding UDT4 fast reliable udp 
> transport to socket.c, as a user-selectable alternative to using default 
> slow TCP?
> It could give a 4 to 10-fold throughput improvement to rsync speed over 
> wide area networks.

If you're seeing that, you must be using an old OS at one/both ends,
or poor TCP settings, or a broken router, or have a very unreliable link.

TCP is generally very good at sustained throughput on WANs, reaching
the network bandwidth limit quickly if there is no congestion, and
sharing it reasonably well when there is congestion.

When it fails, there is usually a fault or silly limit somewhere, and
no assurance that another protocol won't hit the same fault/limit.

What are the bandwidth and delay or your WAN, what OSes are used (with
versions), and what types of connections are involved?

Anyway, if you really want to use UDT4, it is probably better to use a
generic TCP<->UDT4 proxy and point rsync to that.

-- Jamie

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