H3C Technologies H3C SR8800 - Manual (Page 16)

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Figure 5 Label advertisement modes
Figure 5 shows the two label advertisement modes, DU and DoD.
• In DU mode, an LSR assigns a label to a FEC and then distributes the FEC-label binding to its
upstream LSR unsolicitedly.
• In DoD mode, an LSR assigns a label to a FEC and distributes the FEC-label binding to its upstream
LSR only when it receives a label request from the upstream LSR.
NOTE:
•
The device supports only the DU mode.
• An upstream LSR and its downstream LSR for an FEC must use the same label advertisement mode;
otherwise, no LSP can be established normally.
2. Label distribution control modes
Two label distribution control modes are available: independent and ordered.
In independent mode, an LSR can distribute label bindings upstream at anytime. This means
that an LSR may have distributed a label binding to its upstream LSR before it receives a
binding from its downstream LSR. As shown in Figure 6 , in independent label distribution
control mode, if the label advertisement mode is DU, an LSR will assign labels to its upstream
even if it has not obtained labels from its downstream; if the label advertisement mode is DoD,
the LSR distributes a label to its upstream as long as it receives a label request from the
upstream.