LDP provides two LSP control modes:
Using independent LSP control, each LSR makes independent decisions to bind labels to FECs. By contrast, using ordered LSP control, the initial label for an LSP is always assigned by the egress LSR for the associated FEC (either in response to a label request message or by virtue of sending an unsolicited label mapping message).
More specifically, using ordered LSP control, an LSR only binds a label to a particular FEC if it is the egress LSR for the FEC, or if it has already received a label binding for the FEC from its next hop for the FEC. True to its name, the mode provides a more controlled environment that yields benefits such as preventing loops and ensuring use of consistent FECs throughout the network.
The Extreme MPLS implementation supports ordered LSP control only.