In a Multi-protocol label switching (MPLS) network, which component is responsible for pushing an MPLS label onto the front of an incoming Internet Protocol (IP) packet?

The component responsible for pushing an MPLS label onto the front of an incoming Internet Protocol (IP) packet is the Label Edge Router (LER). LERs are situated at the edge of an MPLS network and play a critical role in the process of assigning labels to packets that enter the MPLS domain. When an incoming IP packet arrives at the LER, it evaluates the packet based on predefined rules and policies. If the packet is to be forwarded within the MPLS network, the LER attaches an MPLS label to it, essentially wrapping the original IP packet with MPLS context.

This labeled packet is then forwarded into the core of the MPLS network, where Label Switch Routers (LSRs) make forwarding decisions based on the MPLS labels rather than the IP address. The critical function of the LER in this process ensures that the packets are appropriately labeled before they enter the more complex switching fabric of the network, thus facilitating efficient data routing.

Understanding the role of LERs in MPLS is fundamental for grasping how MPLS effectively manages network traffic by providing a mechanism for making routing decisions based on labels rather than network layer addressing.