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

### Test setup

Sender node:
  * Intel(R) Core(TM) i5-2540M CPU @ 2.60GHz
  * 8 GiB Ram
  * Intel 82579LM Gigabit Network
  * Ubuntu 14.04 (Kernel 3.13.0-65-generic)

Receiver node:
  * Intel(R) Core(TM) i5-3450 CPU @ 3.10GHz
  * 16 GiB Ram
  * Realtek RTL8111/8168/8411 Gigabit Network
  * Ubuntu 14.04 (Kernel 3.13.0-63-generic)

VpnCloud version: `VpnCloud v0.3.0, protocol version 1, libsodium 1.0.7 (AES256: true)`

The sender runs the following command:

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

and the receiver runs:

```
$> ./vpncloud -t tap -l RECEIVER:3210 -c SENDER:3210 \
   --ifup 'ifconfig $IFNAME 10.2.1.2/24 mtu 1400 up' &
$> iperf -s &
$> top
```

For encrypted tests, `--shared-key test --crypto METHOD` is appended.


### Throughput

The throughput is measured with the following command:

```
$> iperf -c DST -t 60
```

The test is run in 3 steps:
* Native throughput without VpnCloud (`DST` is the native address of the receiver)
* Throughput via VpnCloud (`DST` is `10.2.1.2`)
* Encrypted throughput via VpnCloud (`DST` is `10.2.1.2`)


| Throughput test               | Bandwidth     | CPU usage (one core) |
| ----------------------------- | ------------- | -------------------- |
| Without VpnCloud              | 926 Mbits/sec |  -                   |
| Unencrypted VpnCloud          | 873 Mbits/sec | 80% / 95%            |
| Encrypted VpnCloud (ChaCha20) | 770 Mbits/sec | 100%                 |
| Encrypted VpnCloud (AES256)   | 835 Mbits/sec | 90% / 100%           |


### Latency

The latency is measured with the following command:
```
$> ping DST -c 100000 -i 0.001 -s SIZE -U -q
```

For all the test, the best average RTT out of 5 runs is selected. The latency is
assumed to be half of the RTT.


| Payload size                  | 100 bytes | 500 bytes | 1000 bytes |
| ----------------------------- | --------- | --------- | ---------- |
| Without VpnCloud              | 158 µs    | 164 µs    | 171 µs     |
| Unencrypted VpnCloud          | 217 µs    | 227 µs    | 242 µs     |
| Difference                    | +59 µs    | +63 µs    | +71 µs     |
| Encrypted VpnCloud (ChaCha20) | 231 µs    | 245 µs    | 259 µs     |
| Difference                    | +14 µs    | +18 µs    | +17 µs     |
| Encrypted VpnCloud (AES256)   | 223 µs    | 237 µs    | 251 µs     |
| Difference                    |  +6 µs    | +10 µs    |  +9 µs     |


### Conclusion

* VpnCloud achieves over 850 MBit/s with default MTU settings.
* In encrypted mode, VpnCloud reaches over 800 MBit/s with default MTU settings.
* VpnCloud adds about 70µs to the latency.
* Encryption adds an additional latency up to 20µs depending on the packet size.