I disagree.
I maintained ADSM on an IBM SP node with 100mb ethernet & FDDI.  Other boxes
being backed up on FDDI were originally coming through the routers &
switches through the 100mb card on our server.  Its throughput was about
that of a 10mb ethernet LAN.  Our LAN personnel spoke of the overhead of the
routers & switches changing ethernet to FDDI traffic.  Backup speed resumed
at several MB/sec after we added a FDDI card to the ADSM server.  I know
virtually nothing about LAN configuration.  Fortunately we were able to
throw money at the problem in the form of a FDDI card to provide a cure.
Others may be successful in LAN tuning.

Randy Eggert
MAPCO, Inc.