What Is the Actual Network Speed of a VPN Connection?

A VPN connection has been created. Two ECSs have been created with one at the local end and the other at the remote end. The two ECSs can ping each other.

Perform the following steps to test the network speed of your VPN gateway if the bandwidth of your VPN gateway is 200 Mbit/s:

1. If the ECSs at the two ends of the VPN run Windows, use iPerf3 and FileZilla (a free FTP application for file uploading and downloading) to test the network speed.
   

   The test shows that the average network speed of the VPN is 180 Mbit/s, and there is about 10% network speed deviation. The TCP and FTP protocols have the congestion control mechanism, and the IPsec protocol adds a new IP header. Therefore, about 10% network speed deviation is normal for the VPN network.

   Figure 1 shows the test result.

   Figure 1 Test result for 200 Mbit/s bandwidth (iPerf3 client)
   

   Figure 2 shows the test result.

   Figure 2 Test result for 200 Mbit/s bandwidth (iPerf3 server)
   
2. If the ECSs at the two ends of the VPN run CentOS 7, use iPerf3 to test the network speed. The network speed can reach 180 Mbit/s.
3. If the ECS functioning as the server runs CentOS 7, and the ECS functioning as the client runs Windows, use iPerf3 and FileZilla to test the network speed.

   The network speed is about 20 Mbit/s, a slow network speed. That is because TCP implementations on Windows and that on Linux are different. Therefore, if the ECSs at the two ends of the VPN run different OSs, the VPN network speed does not meet the bandwidth requirements.

   Figure 3 shows the test result.

   Figure 3 Test result when ECSs at the two ends run different OSs (iPerf3)
   

Perform the following steps to test the network speed of your VPN gateway if the bandwidth of your VPN gateway is 1,000 Mbit/s:

The VPN gateway bandwidth is shared by all of its VPN connections. If the bandwidth size is large, multiple ECSs are required to test the VPN gateway bandwidth because the forwarding performance of an ECS is limited. This scenario has high requirements on ECS specifications. The ECSs must have NICs that support the bandwidth of 2 Gbit/s or higher.

Conclusions: Based on the preceding test results, bandwidths of VPN gateways meet requirements. To fully use your purchased bandwidth, you are advised to use servers running the same operating system and using NICs meeting certain requirements at the two ends of a VPN connection.