Performance Tests
-----------------

### Test setup

Two nodes with:
  * 2x Intel(R) Xeon(R) CPU L5420
  * 16 GiB Ram
  * Intel Corporation 80003ES2LAN Gigabit Ethernet Controller (Kernel driver e1000e)
  * Debian Linux 7.0 (Kernel 2.6.32-26-pve)
  * Connected by Cisco Catalyst 4506 switch

VpnCloud version: `VpnCloud v0.1.0 (without crypto support, protocol version 1)`


### Test 1: Unencrypted throughput

Node 1:
```
$> ./vpncloud -t tap -l NODE1:3210 -c NODE2:3210 \
   --ifup 'ifconfig $IFNAME 10.2.1.1/24 mtu MTU up' &
```

Node 2:
```
$> ./vpncloud -t tap -l NODE2:3210 -c NODE1:3210 \
   --ifup 'ifconfig $IFNAME 10.2.1.2/24 mtu MTU up' &
$> iperf -s &
$> top
```

First, the test is run **without VpnCloud**:
```
$> iperf -c NODE2 -t 60
```

and then **via VpnCloud**:
```
$> iperf -c 10.2.1.2 -t 60
```

**Results:**
  * Throughput without VpnCloud: 938 Mbits/sec
  * Throughput via VpnCloud (MTU=1400): 363 Mbits/sec
  * CPU usage for VpnCloud (MTU=1400): maxed out at ~105% of one core
  * Throughput via VpnCloud (MTU=16384): 946 Mbits/sec (no idea why this is higher)
  * CPU usage for VpnCloud (MTU=16384): ~73% of one core


### Test 2: Unencrypted ping

Node 1:
```
$> ./vpncloud -t tap -l NODE1:3210 -c NODE2:3210 \
   --ifup 'ifconfig $IFNAME 10.2.1.1/24 mtu 1400 up' &
```

Node 2:
```
$> ./vpncloud -t tap -l NODE2:3210 -c NODE1:3210 \
   --ifup 'ifconfig $IFNAME 10.2.1.2/24 mtu 1400 up' &
```

Each test is first run without VpnCloud:
```
$> ping NODE2 -c 1000 -i 0.01 -s SIZE -U -q
```

and then with VpnCloud:
```
$> ping 10.2.1.2 -c 1000 -i 0.01 -s SIZE -U -q
```

SIZE: 50 bytes
  * Without VpnCloud: Ø= 200 µs, stddev= 28 µs
  * With VpnCloud: Ø= 318 µs, stddev= 26 µs

SIZE: 500 bytes
  * Without VpnCloud: Ø= 235 µs, stddev= 29 µs
  * With VpnCloud: Ø= 351 µs, stddev= 26 µs

SIZE: 1400 bytes
  * Without VpnCloud: Ø= 303 µs, stddev= 32 µs
  * With VpnCloud: Ø= 421 µs, stddev= 31 µs


### Conclusion

* VpnCloud achieves about 360 MBit/s with default MTU settings.
* At increased MTU, VpnCloud is able to saturate a Gigabit link.
* VpnCloud adds about 120µs to the round trip times, i.e. 60µs latency increase.