Transport Performance / Protocol Overhead (remote shell vs daemon)

[Matt McCutchen]

On 5/29/07, Matt <langelino at gmx.net> wrote:
> note that with  #1 you are doing TCP over TCP which is usually regarded
> as sub-optimal, see http://sites.inka.de/~W1011/devel/tcp-tcp.html.

No, I do not think #1 involves any TCP over TCP.  If the rsync client
connected directly to the daemon's port, the daemon would receive the
raw rsync data stream, not a stream representation of TCP packets.
The same is true when the rsync client connects to the port forwarded
by ssh.  The ssh client and server pass the raw rsync data stream back
and forth over TCP.  Nowhere is a stream representation of TCP packets
itself being sent over TCP.  Another way to say it: #1 can't be TCP
over TCP because it involves no analogue to PPP.

> Wayne S., if you are always running  the same rsync, you may also like
> to  consider using a ssh with public-key authentication and  forced
> command.

Addendum: It's almost always better to force an appropriately
configured single-use rsync daemon than a particular rsync server
command.   See https://bugzilla.samba.org/show_bug.cgi?id=4163 .

Matt McCutchen