Networking :: IP Layer Link Aggregation Without Switch Support

I'm looking for a way (kernel patches, configuration, etc) to bond multiple network interfaces together but for limited purposes. Here's the setup. Machines A, B, C, and D each have 4 NICs, each of which are on separate unmanaged switches. The connections are made in a corresponding way. e.g. eth0 of each machine are connected via switch 0, eth1 are connected via switch 1, etc. There are also other machines which have only one NIC and are connected to switch 0 only. All NICs for A/B/C/D and the switches are gigabit speed. The remaining machines have a low traffic level. Machines A/B/C/D need the extended bandwidth. And this bandwidth need usually involves only one connection at a time.

E.g. machine A transferring files to machine C with no other traffic going on. The speed need is to cut the transfer times from several hours to few hours (such as 8 hours to 2 hours). Transfers of up to a few terabytes at a time are involved. IEEE 802.1AX won't accomplish this. It requires special support from a single switch that all connection go to (raising costs and reducing reliability). Also, from technical details of 802.1AX, it appears that a decision process is made for which traffic goes over which physical link based on destination information. It's unclear what impact this will have, but it looks like at least a single TCP connection cannot use all physical links.

And possibly all traffic from host A to host B is limited to a physical link (not any better than a round robin of crossover cables). What I am looking for is something that works entirely on an end-to-end basis within a LAN. If it works at the link layer, that could be OK as long as it doesn't have the limitations of 802.1AX. Working at the IP layer would be OK, too (as I can already envision the logic of how to make that work). This might be an experimental patch to the Linux kernel if anyone has tried it. I have not dug into kernel source to see what might be in there, yet, but will eventually do that if there isn't a patch already available.