Ways to optimize performance in pipelines over network (RSH and SSH)

Consider a data transfer over a pipeline network in legacy systems with remote shell (RSH), like: rsh host -l user tar -cf - /home/dir \| compress | uncompress | tar -xvf - and this one in 'modern' systems: ssh user@host tar -cf - /home/dir \| gzip | ungzip | tar -xvf - **PERFORMANCE ISSUES:** I experienced a very bad performance running a transfer among AIX 4.3 to AIX 5.3 using RSH. Even having idle cards (10/100) connecting them through an idle switch, I got a performance about 350Kbps transferring 5.4GB. When running this transferring among AIX 5.3 and Linux, but now using SSH and gzip, the performance is way better, but never reachs the network capacity (In a 1 Gigabit LAN I got an average of about 400Mbps). Are there ways to optimize the network pipeline performance maybe customizing pipe buffers or network block/buffers, or what ?