H3C Technologies H3C S10500 Series Switches - Manual (Page 62)

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Figure 16 Label advertisement modes
The label advertisement modes shown in Figure 16 are described as follows:
• 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 switch supports only the DU mode.
• An upstream LSR and its downstream LSR must use the same label advertisement mode; otherwise, no
LSP can be established.
2. Label distribution control modes
Label distribution control modes include 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 for a FEC to its upstream LSR before it receives a binding
for that FEC from its downstream LSR. As shown in
Figure 17 , 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.