I am astounded, I hacked an iperf implementation for the board and increased lwip parameters so I could run 10 parallel streams.
Here is the result connecting from a Mint 17.1 Linux PC:
bill@mint17 ~ $ iperf -c192.168.2.20 -P10
------------------------------------------------------------
Client connecting to 192.168.2.20, TCP port 5001
TCP window size: 85.0 KByte (default)
------------------------------------------------------------
[ 12] local 192.168.2.172 port 56861 connected with 192.168.2.20 port 5001
[ 4] local 192.168.2.172 port 56853 connected with 192.168.2.20 port 5001
[ 3] local 192.168.2.172 port 56852 connected with 192.168.2.20 port 5001
[ 6] local 192.168.2.172 port 56855 connected with 192.168.2.20 port 5001
[ 5] local 192.168.2.172 port 56854 connected with 192.168.2.20 port 5001
[ 8] local 192.168.2.172 port 56857 connected with 192.168.2.20 port 5001
[ 7] local 192.168.2.172 port 56856 connected with 192.168.2.20 port 5001
[ 9] local 192.168.2.172 port 56858 connected with 192.168.2.20 port 5001
[ 10] local 192.168.2.172 port 56859 connected with 192.168.2.20 port 5001
[ 11] local 192.168.2.172 port 56860 connected with 192.168.2.20 port 5001
[ ID] Interval Transfer Bandwidth
[ 4] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 3] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 6] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 8] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 7] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 9] 0.0-10.1 sec 11.5 MBytes 9.53 Mbits/sec
[ 12] 0.0-10.1 sec 11.2 MBytes 9.31 Mbits/sec
[ 5] 0.0-10.1 sec 11.5 MBytes 9.52 Mbits/sec
[ 10] 0.0-10.1 sec 11.5 MBytes 9.52 Mbits/sec
[ 11] 0.0-10.1 sec 11.5 MBytes 9.52 Mbits/sec
[SUM] 0.0-10.1 sec 115 MBytes 95.0 Mbits/sec
The result is 95 Mbit/sec for any parallelism from 1 to 10. Wow!