Another approach to further fine-tune the access controls on the network level is to introduce labeled networking. With labeled networking, security information is passed on between hosts (unlike SECMARK, which only starts when the packet is received by the netfilter subsystem). This is also known as peer labeling, as the security information is passed on between hosts (peers).
The advantage of labeled networking is that security information is retained across the network, allowing an end-to-end enforcement on mandatory access-control settings between systems as well as retaining the sensitivity level of communication flows between systems. The major downside however is that this requires an additional network technology (protocol) that is able to manage labels on network packets or flows.
SELinux currently supports two implementations as part of the labeled networking approach: NetLabel and labeled IPsec. With NetLabel, two implementations exist: fallback labeling and CIPSO...