data plane
also: forwarding plane, fast path
The data plane is the part of a network or system responsible for forwarding and processing actual user data traffic, as opposed to control messages.
The data plane (also called the forwarding plane) handles the real work of moving data packets from source to destination. It operates on individual packets or frames and applies rules determined by the control plane, such as routing decisions or firewall policies.
In contrast, the control plane handles management, routing protocol exchanges, and policy configuration—the "thinking" part of the system. For example, in a router, the control plane runs routing protocols like BGP to build routing tables, while the data plane uses those tables to actually forward packets.
A concrete example: in a Linux firewall using iptables or nftables, the control plane is you writing the rules and the kernel processing them, while the data plane is the kernel rapidly filtering millions of packets through those rules. Modern high-performance systems often implement the data plane in hardware or specialized kernel subsystems for speed.