Which technology is primarily used for session encryption in web services?

SSL (Secure Sockets Layer) is the technology primarily used for session encryption in web services, which is crucial for securing data transmitted over the internet. SSL provides a secure channel between two devices, typically a web server and a client (browser), ensuring that any data exchanged during a session remains confidential and integral.

When a user connects to a secure website, SSL establishes an encrypted link, preventing unauthorized parties from intercepting or tampering with the data. This is critical for protecting sensitive information, such as credit card numbers or personal details, during online transactions.

Other options like SSH (Secure Shell) are primarily used for secure remote login and command execution, while IPsec focuses on securing internet protocol communications at the network layer. PPTP (Point-to-Point Tunneling Protocol) is used for implementing virtual private networks but does not offer the same level of security or is not as widely used for web session encryption compared to SSL. Thus, SSL's specific application in web services makes it the correct choice.