When implementing Internet Protocol security (IPsec) architecture, the servers involved in application delivery communicate via Transport Layer Security (TLS), which is a protocol that provides encryption and authentication for data transmitted over a network. IPsec operates at the network layer and provides security for IP packets, while TLS operates at the transport layer and provides security for TCP connections. Blocking authorized users from unauthorized activities, channeling access only through the public-facing firewall, and channeling access through authentication are not functions of IPsec architecture. References: CISA Review Manual (Digital Version), Chapter 5, Section 5.4.2