The Label Forwarding Information Base (LFIB) is a specialized table used in Multiprotocol Label Switching (MPLS) networks to make forwarding decisions based on labels attached to packets, rather than traditional IP address lookups. MPLS is a data-carrying technique for high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses.
In an MPLS router, three main tables are used to direct traffic:
- Label Information Base (LIB): This contains all labels that the router might use, including local labels, and maps them to their corresponding network layer information.
- Label Forwarding Information Base (LFIB): It maps incoming labels to the outgoing label operations, such as swap, push, or pop, and the corresponding outgoing interfaces. This is what makes LFIB distinct from the traditional FIB (Forwarding Information Base) used in non-MPLS networks, which typically uses IP addresses to make forwarding decisions.
- Label Distribution Protocol (LDP): This table, sometimes considered part of the LIB, handles label distribution among MPLS-enabled routers to ensure that label mappings are consistent across the network.
The LFIB plays a critical role in the high-speed forwarding of packets within an MPLS network by simplifying the packet processing needed. This efficiency is achieved by using fixed-length labels in the headers that are easier to process than IP addresses, enhancing the speed and performance of network traffic routing.