The S-Series platforms support ordered distribution control mode as defined in RFC 5036. In ordered distribution control mode, an LSR may initiate the transmission of a label mapping only for a FEC for which it has a label mapping for the FEC next hop, or for which the LSR is the egress. If neither of these conditions holds, the LSR must wait until a label from a downstream LSR is received before mapping the FEC and passing corresponding labels to upstream LSRs.
The ordered approach helps to provide loop prevention, but at the cost of requiring a longer amount of time to set up a label switched path.
MPLS LDP label distribution control is not administratively configurable in this release and is hard coded for ordered distribution control mode.