I have two Linux machines that I wish to connect via a bonded link.
One machine has two UMTS modems (DN:5mbit UL:1.2mbit) as its gateways, and the other machine has optical fiber (DL:100Mbit UL: 20mbit) as its gateway.
I can successfully create 2 OpenVPN channels (one per UMTS modem, using iptables rules) and have applied the Linux bonding driver (mode 0, round robin distribution) to these channels.
So far, so good. The bonded interface connects the two Linux machines via two aggregated VPN channels, where I can ping each machine, transfer files, etc, etc.
My problem is the bandwidth of the bond. Theoretically the bandwidth should double, but in fact, it is the same, independent of the number of VPN connections inside the bond.
In the machine with two UMTS modems, when I use only one VPN, I can reach the other machine with bandwidth near DN:5mbit UL:1.2mbit. Using 2 VPNs inside the bond interface the bandwidth per channel is near DN:2.5mbit UL:0.6mbit, so the overall bandwidth is the same, whether I use one or both VPN channels.
This behavior happens when I transfer data using either TCP or UDP, so it isn't a protocol issue.
Has anyone else experienced this too?
Thanks in advance.