Control Plane

• Responsible to exchange topology information with other routers and build Routing Information Base based on IGP or EGP
• Makes decisions about where traffic is sent
• Also responsible for connectivity management (BFD, CFM)
• Adjacent device discovery (hello mechanism which are used in routing protocols such as IS-IS, ARP e.t.c)
• Service Provisioning (RSVP for IntServ or MPLS/TE)

Forwarding Plane

• Also known as User/ Data/ Carrier or bearer plane.
• Forwards traffic to the next hop according to control plane logic
• Also responsible for NAT session creation and NAT table maintenance
• ACL Logging, Error Signaling, Networking Accounting

Management Plane

• Provides a single entry point to the system for user configuration, handles user queries, and performs operational tasks on all management, control, and data plane nodes.

Scenario

Consider the following scenario. 

Let’s say a Telnet session is established from R1 to R3. On both R1 and R3, these packets are handle by the control plane, forwarding plane and management plane. However from R2’s perspective, this is just data plane traffic that is transiting between links.