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The IPsec protocols AH and ESP can be implemented in a host-to-host transport mode, as well as in a network tunneling mode.
Transport mode - only the payload of the IP packet is usually encrypted or authenticated. The routing is intact, since the IP header is neither modified nor encrypted. The transport and application layers are always secured by a hash, so they cannot be modified in any way, for example by translating the port numbers.
Tunnel mode - the entire IP packet is encrypted and authenticated, then encapsulated into a new IP packet with a new IP header. Tunnel mode is used to create virtual private networks for network-to-network communications (e.g. between routers to link sites), host-to-network communications (e.g. remote user access) and host-to-host communications (e.g. private chat).
https://en.wikipedia.org/wiki/IPsec