I think I got it! It just occurred to me to test the following scenario:
1. Disable pppoe0 in load balancer, leaving pppoe1 up.
2. Start d/l (4-way, but I don’t think it matters)
3. Enable pppoe0.
4. Add d/l segment. D/l rate goes immediately to 1.0 MB/s which is very close to 2×5000 Mbit/s.
So there is something wrong with load balancer, with the way it distributes TCP connections among the pppoe interfaces.
Another test case is as follows:
1. Disable pppoe0 in balancer
2. start single-segment d/l on machine #1 – speed reaches 532-534 KB/s
3. Enable pppoe0 in balancer
4. Start single-segment d/l on machine #2 – speed reaches 532-534 KB/s
Simply starting two d/l on two separate machines results in 260 KB/s d/l rate on each machine.
This is reproducible.
Fulvio, can you have a look at the load balancing algorithm?