It may seem odd and even confusing that rsync appears to rely on other commands to move files. Is it a file-transfer utility, or isn't it? The answer is an emphatic yes.
First, rsync can operate without the assistance of external transport mechanisms if your remote host is running rsync in dæmon mode. rsync even has its own privileged listening port for this purpose: TCP 873.
Second, remember that rsync was invented not because existing methods couldn't move data packets efficiently, but because existing methods didn't have the intelligence to determine which data packets or how many data packets actually need moving in the first place. rsync adds this intelligence to SSH and rcp without, as it were, reinventing the packet-moving wheel.
