CCIE SP MPLS FAQ: Cell-mode MPLS Operation
Figure: SuperCell Network—ATM Implementation
Q1. Because IP packets cannot be exchanged directly between two adjacent
Answer: A control-VC is necessary so that control plane information can be exchanged.
Q2. What is an LC-ATM interface?
Answer: Any interface on a router or ATM switch in which the VPI/VCI values are assigned through an MPLS control protocol.
Q3. Which label-distribution method is utilized across an LC-ATM interface?
Answer: Downstream-on-demand label distribution.
Q4. Which label-allocation method does a cell-mode implementation use?
Answer: Ordered control label allocation.
Q5. Which label retention method does a cell-mode implementation use?
Answer: Conservative label retention.
Q6. What is the benefit of using VC-merge?
Answer: Using VC-merge reduces the amount of label space an ATM-LSR requires.
Q7. Why are labels not distributed to upstream neighbors without having received a label mapping from a downstream neighbor?
Answer: To make sure that a complete LFIB entry is available to facilitate correct label switching through the ATM switching matrix.
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