Multi-Protocol Label Switching (MPLS) networks are composed of two primary planes: the Control Plane and the Data Plane. These two planes play distinct roles in the operation of MPLS networks:
Control Plane:
- Route Decision and Label Assignment: The Control Plane is responsible for making routing decisions and assigning MPLS labels to packets. It determines the path a packet should take through the network and the labels to be associated with it.
- Routing Protocols: Control Plane routers use routing protocols like OSPF (Open Shortest Path First) or BGP (Border Gateway Protocol) to exchange routing information and make informed decisions about label assignments.
- Label Distribution: The Control Plane is responsible for distributing label information to all routers within the MPLS network. This is typically done using protocols like LDP (Label Distribution Protocol) or RSVP-TE (Resource Reservation Protocol-Traffic Engineering) for Traffic Engineering.
- Label Binding: In MPLS VPNs, the Control Plane is also responsible for binding customer routes to specific labels, ensuring that customer traffic remains isolated from other VPNs.
Data Plane:
- Packet Forwarding: The Data Plane is responsible for the actual forwarding of labeled packets through the network. It uses the labels assigned by the Control Plane to make forwarding decisions.
- Label Swapping and Popping: Routers in the Data Plane perform label swapping, popping, and pushing as packets traverse the network. They determine the next hop for each packet based on the label at the top of the stack.
- Fast and Deterministic Forwarding: The Data Plane is designed for fast and deterministic packet forwarding. Routers make forwarding decisions based on the MPLS label, avoiding the need for complex IP header lookups.
- Traffic Engineering: In MPLS networks with Traffic Engineering, the Data Plane ensures that packets follow the preconfigured paths and resource reservations established by the Control Plane.
In summary, the Control Plane handles the high-level routing decisions, label assignments, and distribution of label information, while the Data Plane is responsible for the actual forwarding of labeled packets based on the information provided by the Control Plane. This separation of control and data planes is a key feature of MPLS networks, allowing for efficient and flexible packet forwarding and routing.