H3C Technologies H3C S10500 Series Switches - Manual (Page 61)

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A dynamic LSP is established in the following procedure:
A downstream LSR classifies FECs according to destination addresses. It assigns a label to a FEC, and
distributes the FEC-label binding to its upstream LSR, which then establishes an LFIB entry for the FEC
according to the binding information. After all LSRs along the packet forwarding path establish a LFIB
entry for the FEC, an LSP is established for packets of this FEC.
Figure 15 Process of dynamic LSP establishment
Label distribution and management
An LSR informs its upstream LSRs of labels assigned to FECs through label advertisement. The label
advertisement modes include downstream unsolicited (DU) and downstream on demand (DoD). The
label distribution control modes include independent and ordered.
Label management specifies the mode for processing a received label binding that is not useful at the
moment. The processing mode, called “label retention mode,” can be either liberal or conservative.
1. Label advertisement modes