Label Assignment and Distribution
Label Assignment and Distribution. Introducing MPLS Label Allocation, Distribution, and Retention Modes. Outline. Overview Label Distribution Parameters Distributing Labels Allocating Labels Retaining Labels Summary. Label Distribution Parameters.
Label Assignment and Distribution
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Presentation Transcript
Label Assignment and Distribution Introducing MPLS Label Allocation, Distribution, and Retention Modes
Outline • Overview • Label Distribution Parameters • Distributing Labels • Allocating Labels • Retaining Labels • Summary
Label Distribution Parameters • Frame-mode MPLS architecture defines several label allocation and distribution parameters: • Per-platform label space • Unsolicited downstream label distribution • Independent label allocation control • Liberal label retention
Label Distribution: Unsolicited Downstream • The label for a prefix is allocated and advertised to all neighbor LSRs, regardless of whether the neighbors are upstream or downstream LSRs for the destination.
Label Allocation: Independent Control • An LSR can always assign a label for a prefix, even if it has no downstream label. • Independent control can be used only for LSRs with Layer 3 capabilities.
Label Retention: Liberal Retention Mode • Each LSR stores the received label in its LIB, even when the label is not received from a next-hop LSR. • Liberal label retention mode improves convergence speed.
Summary • There are four MPLS label distribution parameters: label space, label distribution, label allocation, and label retention. • Frame-mode MPLS distributes labels using downstream unsolicited label distribution • Frame-mode MPLS allocates labels to neighbors using independent control • Frame-mode MPLS uses liberal label retention
