To keep the company's data secure, the VPN protects any traffic that takes place. (Encrypted Traffic) One option is to use the Advanced Encryption Standard (AES), or to use different protocols such as IPsec (Internet Protocol Security) or L2TP (Layer 2 Tunneling Protocol) to protect the content of your traffic and make it unreadable for non-authorized users.

To explain in more detail how the Protocols work:

IPsec VPN protects point-to-point communication by establishing secure tunnels between hosts, between hosts and network security gateways, or between network security gateways (such as routers and firewalls). It operates at the IP layer to encrypt and authenticate data packets.

Compared with other VPN technologies, IPsec VPN is more secure because data is encrypted for transmission in IPsec tunnels.

Layer 2 Tunneling Protocol (L2TP) connections, which are also called virtual lines, provide cost-effective access for remote users by allowing a corporate network systems to manage the IP addresses assigned to its remote users. Further, L2TP connections provide secure access to your system or network when you use them in conjunction with IP Security (IPSec).

A Site2Site VPN is helpful if each site either develops its own resources or houses unique processes that the entire company would benefit from having access to.

Access Controll - Some network resources should only be accessible internally, meaning employees should have access, but external users should not. With an S2S VPN, users are internal users, so access control rules are easier to define. This is because any traffic coming from different sources can be blocked from accessing those resources.

Simplified network architecture - Organizations commonly use internal ip address ranges for their devices within the LAN, these need to be converted to external addresses in order to access the public internet.

This does not happen with S2S VPN, the traffic stays on the internal LAN, so all sites are able to use internal IP addresses for each other's resources.