in IPSec, is useful for protecting traffic between different networks, when traffic must pass through an intermediate, untrusted network. This is primarily handled from Firewall to Firewall and thus leaves the data unprotected within the internal network.

$\_$Supposed to be as secure as wired LAN connections, but lacks the physical security of controlling the ports.

$q,$ is the default mode for IPSec, and it is used for end$-$to$-$end $($Host$-$to$-$Host$)$ communications. In this mode, IPSec encrypts only the IP payload.

Encrypted replacement for Telnet. Can use Public Keys, Digital Certs, or passwords for Authentication

provides authentication, integrity, and anti$-$replay protection for the entire packet $($both the IP header and the data payload carried in the packet$)$ in IPSec. It does not provide confidentiality $($by itself$).$