H3C Technologies H3C S7500E Series Switches - Manual (Page 47)

2-5
Figure 2-4 Process of dynamic LSP establishment
LSR A LSR B LSR D LSR C
LSR E LSR F LSR G
LSR H
Ingress Egress
LSP
Label mapping
Label distribution and management
An LSR informs its upstream LSRs of labels assigned to FECs through label advertisement. According
to the label distribution condition and order, the label advertisement mode can be downstream
unsolicited (DU) and downstream on demand (DoD), and the label distribution control mode can be
independent or ordered.
Label management refers to the processing of a received label binding that is not useful at the
moment, that is, the label retention mode, which can be liberal or conservative.
1) Label advertisement mode
Figure 2-5 Label advertisement mode
Figure 2-5 shows the two label advertisement modes:
z
DU: In this mode, an LSR assigns a label to a FEC and then distributes the FEC-label binding to
its upstream LSR unsolicitedly.