@Dave Lonsdale - yeah on that machine and 1 image sent to DS, I would expect it to not max out.
I suspect a setting is wrong on your network cards to limit it to 100MB - they are probably 1gig cards that got reset after an update or something crazy.
I had that happen once or twice. Go into the network settings and many times the speed of the card is right in the name of the card you have. Hopefully it says giga.
If so, disable the card momentarily and then turn it back on. If that doesn't fix it, then do the Diagnose button and see if that corrects it.
If you indeed have a 100MB card and you are seeing performance issues, you can pick up a giga card fairly cheap and replace it.