How does IPsec secure communications within an organization?

IPsec secures communications by establishing Security Associations (SAs) between two communicating peers. An SA is a bundle of algorithms and parameters (like encryption keys, authentication methods, and security protocols) that are negotiated and agreed upon for secure communication. This negotiation occurs during the Internet Key Exchange (IKE) phase of IPsec. FTP and TFTP are application-layer protocols primarily for file transfer and do not inherently provide the comprehensive network layer security that IPsec offers. GRE tunnels can encapsulate traffic, but they do not provide encryption or authentication on their own; they can be secured by IPsec, but GRE itself is not the core security mechanism of IPsec.