How to improve performance of impdp over a network_link

Source database:  RDBMS 11.1.0.7 RAC on OEL 5 1 gb NIC

Target database:   RDBMS 12.1.0.2 on OEL 6 10 gb NIC fiber interconnect with dual links = 20 gb NIC

I am importing a large amount of data over a network_link.  The target database is on a Cisco UCS blade, and we've upgraded our network as well.  Jumbo frames are not enabled on either server, though we can do that.

Our network guys are monitoring what we are doing, and they see a throughput throttled at around 200mb during the impdp with network_link.  They then just copied a 1gb file from one server to another and saw the transfer rate tick up to 1gb. So it looks like the impdp is ratcheting down the transfer.