A data plane, or forwarding plane, is the part of a router that examines an incoming data packet and sends it to the correct output destination on the network. A data packet header contains information about where the packet came from and where it needs to go, which the data plane uses to direct network traffic.
The data plane accesses a table, sometimes called a router table, which retrieves previously listed IP addresses to which a packet can be sent. Sending the packet to the right location is called forwarding. The table will also contain instructions to drop a data packet if it doesn’t meet required specifications. These specifications are based on the router’s configuration and what traffic it can permit on the network.
Some routers have multiple-forwarding capabilities, which allow them to process more packets at a time. Some routers, upon receiving an invalid or forbidden packet, are also configured to send a message to the sender alerting them that their request failed. But some routers have security features that force a data plane to drop packets without sending any notification. This protects the destination IP address from malicious traffic and keeps the sender from knowing more details about the request than they should.
A data plane differs from a control plane, which manages forwarding paths in an entire network—in other words, managing the entire routing process. A data plane is restricted to one router and manages packet forwarding only for it.
Forwarding is considered part of Layer 3 of the OSI model, a seven-layer conceptual model that helps clarify how network connections are processed and completed. Layer 3, known as the Network Layer, manages all the routing and data transmission within a network. IP addresses are also part of the Network Layer.