Hello @Venison Mogambi ,
LDP = Label distribution Protocol
The purpose of LDP is to create local Label bindings for each prefix that can be associated with a label and to advertise the local labels to prefixes bindings to all the neighbors.
As you noted LDP by itself does not provide the capability to go beyond what the IGP in use is doing as it follows the lowest IGP metric to install the label coming from the IGP next-hop.
However, MPLS / LDP provides the foundation block of the MPLS forwarding plane allowing internal devices to perform label switching instead of consulting the IP routing table.
This may look like a small advantage but in the big picture of MPLS and MPLS services like MPLS L3 VPN , EoMPLS, various types of L2 VPN, VPLS till to EVPN this is a building block.
MPLS labels can be stacked = multiple MPLS labels can be applied to a packet before forwarding.
The most external label nearest to the L2 header is also called the IGP label is actually provided either by LDP or by RSVP TE.
The inner label represents a service like a L3 VPN prefix or a EoMPLS pseudowire.
The inner label never changes in the path to the destination PE node and it is meaninguful only there.
The external IGP label changes at each router hop and provides a end to end MPLS path to the destination PE loopback interface.
This is the way that LDP and MPLS provide a way to carry traffic (even IPv6 for example) that otherwise cound not be routed by core routers.
This is the real advantage that MPLS and LDP can provide in modern networks, there is no real performance gain in using MPLS.
But MPLS allows to deploy services that do not require awareness for routers in the core.
This provides flexbility and scalability as core routers don't need to have state information about MPLS services.
Hope to help
Giuseppe
