Hello @jahangir7g ,
BGP-LU = BGP labelled unicast allows to use a special purpose address family to exchange IPv4 prefixes with labels.
Labels are taken by BGP from the node MPLS label space.
The advantage of BGP-LU is to avoid to use LDP for exchanging MPLS labels in addition to a unicast routing protocol.
BGP-LU can be used in multi MPLS SP scenarios like inter AS VPN or Carrier Supporting Carrier CSC with the above advantage of protocol reduction.
BGP-LU is also used in seamless MPLS within a single big SP as a way to build a more efficient MPLS network.
With BGP-LU the typically exchanged prefixes are loopback addresses of PE nodes within the local AS in order to allow inter -AS scenarios or CSC scenarios.
End to end LSPs are actually formed by multiple sections that are joined stitched by ASBR node BGP LU speaker that typically uses next-hop self towards internal PE nodes in order to make this join operation.
The end result may be a saving of states #LSPs on the inner core devices that do not need to store actually all the possible end to end LSPs.
This latest aspect can also be achieved with a feature called LDP tunneling that in Cisco implementation requires to activate LDP on MPLS TE tunnels (unidirectionals)
Hope to help
Giuseppe
