OpenSSL cipher speed
OpenVPN uses OpenSSL to perform all cryptographic operations. This means that the performance of an OpenVPN client or server depends on how fast the incoming traffic can be decrypted and how fast the outgoing traffic can be encrypted. For a client with a single connection to the OpenVPN server, this is almost never an issue, but with an OpenVPN server with hundreds of clients, the cryptographic performance becomes very important. Also, when running OpenVPN over a high-speed network link (Gigabit or higher), the cryptographic performance also plays an important role.
In this recipe, we will show how to measure the performance of the OpenSSL cryptographic routines and how this measurement can be used to improve the performance of an OpenVPN server.
Getting ready
This recipe is performed on a variety of computers:
An old laptop with an Intel Core2 Duo T9300 processor running at 2.5 GHz, running Fedora Linux 22 64bit
An older server with an Intel Xeon X5660 processor running...
