Why does SoftEther VPN have a very low Downlink with a normal Uplink?

Question

VPN

Good laziness
I installed the latest version of SoftEther VPN Server on Ubuntu.
As VPN clients: iphone, Windows 8, other server
To measure throughput I used Network Traffic Speed ​​Test Tool from vpncmd:
without VPN : iphone/Windows <-> VPN Server:
Download - 36.88 Mbps
Upload - 4.93 Mbps
with VPN' ohm (L2TP/SSTP/SoftEteher VPN client using Local Bridge/SecureNAT): iphone/Windows <-> VPN Server:
Download - 300.53 Kbps
Upload - 4.79 Mbps
Between servers without VPN : VPN Server <-> Ubuntu
Download - 0.95 Gbps
Upload - 0.92 Gbps
Between servers with VPN : VPN Server <-> Ubuntu
Download - 9.14 Mbps
Upload - 905.33 Mbps
+ DSTAT:
----total-cpu-usage---- -net/total- ---paging-- -- -system--
usr sys idl wai hiq siq| recv-send| in out | int csw
0 0 100 0 0 0| 0 0 | 0 0 |5686 12k
0 0 99 0 0 0| 597B 1631B | 0 0 | 366 710
0 0 99 0 0 0| 6306B 6897B | 0 0 | 514 1242
0 0 99 0 0 0| 13k 14k | 0 0 | 656 1815
6 4 87 0 0 3| 85M 84M | 0 0 |5201 34k
6 4 88 0 0 2| 117M 116M | 0 0 |4836 47k
7 5 86 0 0 3| 114M 114M| 0 0 |5567 45k
6 5 87 0 0 3| 110M 110M | 0 0 |5589 46k
6 3 88 0 0 3| 114M 114M | 0 0 |4772 47k
6 4 87 0 0 2| 114M 114M | 0 0 |5274 47k
6 5 87 0 0 2| 117M 116M | 0 0 |5063 47k
6 5 87 0 0 2| 114M 113M | 0 0 |6064 48k
6 4 87 0 0 2| 114M 114M | 0 0 |5473 44k
6 4 88 0 0 2| 111M 111M | 0 0 |5026 46k
6 5 86 0 0 2| 117M 117M | 0 0 |5187 46k
6 4 88 0 0 2| 117M 116M | 0 0 |4672 48k
6 5 87 0 0 3| 112M 112M | 0 0 |5200 45k
7 5 86 0 0 2| 112M 111M| 0 0 |6414 44k
7 5 87 0 0 2| 117M 116M | 0 0 |4924 48k
2 2 95 0 0 1| 36M 36M | 0 0 |1927 17k
Question: Why is Download via VPN miserable?
PS VPN Server has one eth0.
PPS Between servers via VPN : Download-only - 89.14 Mbps , Upload-only - 0.93 Gbps

Answer 1

The problem was that SoftEther VPN Server was in an LXC container.
SoftEther's Local Bridge messed up.. The
container was unprivileged.
1. Made a new one from under root
2. Added to the container config:
lxc.mount.entry = /dev/net dev/net none bind,create=dir
lxc.cgroup.devices.allow = c 10:200 rwm
3. Created LocalBridge (TAP) in SoftEther: vpn
4. Made a new bridge in container br0 between eth0 and tap_vpn

Answer 2

Perhaps the entropy pool is not enough for such an encryption stream. Try installing the haveged daemon.