MPLS label and network exchange

[schmidtjoe]

Hi,

all routers in a MPLS domain need a LIB table.

To build the LIB table routers in a MPLS domain need to use LDP to exchange the labels with their neighbors via multicast. Meanwhile the LIB is kind of a "mapping table" of netowrk, MPLS label and next hop router. What is the mechanism in a router to associate the network with the label from its neighbor and entroll them(network + label) to the LIB?

e.g. a LIB entry in R1 as I understand seems like:

destination network: 10.0.0.0/24 (from underlying protocol? and how to associate with the label?) -- label: 55 (LDP exchange from R2) -- next hop/via: R2

[MHM Cisco World]

If you use GNS3, then run wireshark, 
both router exchange LDP message contain FEC (prefix) and label 
FEC is prefix connect to router or any prefix that this router is next-hop, 
label is unique for each FEC. 

Note:-the LDP is unicast not multicast.