
MPLS: MultiProtocol Label Switching ◾ 151
can be propagated downstream in the chain of LSR until it is received by the
egress LER.
Label Request Response: ◾ A downstream LSR on receiving the label request sends
a label to the upstream LSR requestor using a label mapping framework.
Distribution of Labels
Label distribution ensures that neighboring routers have a common view of the
FEC requirements through the label bindings. Because labels are created based on
the FECs, then to make label swapping possible, a uniform and clear understand-
ing of which FECs map to which labels must be established between adjacent rout-
ers (LDP adjacencies). e ...