Source Routed Multicast LSP via Hierarchical Label Stacking
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Solution Overview
Problem
Conventional MPLS techniques face scalability issues in handling multicast operations due to their linear structure, leading to duplicated packets and increased network traffic in non-linear multicast scenarios.
Innovation Solution
The introduction of new operations such as popN and copy&pop on the label stack allows for efficient processing and delivery of packets along pre-computed multicast distribution trees, reducing duplicated packets and improving scalability by encoding multicast trees using a stack of MPLS compatible labels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional MPLS techniques are used for multicast operations, then packets can be delivered along linear paths, but duplicated packets and increased network traffic occur in non-linear multicast scenarios
Solution Approach 1:
The patent segments the multicast distribution tree into multiple LSPs (Label Switched Paths), where each LSP corresponds to a specific branch or segment of the tree. This segmentation allows packets to be delivered efficiently along each segment without unnecessary duplication, as each LSP handles a specific portion of the multicast traffic.
Solution Approach 2:
The patent introduces a hierarchical dimension to MPLS label stacks by allowing nested LSPs within LSPs. This multi-dimensional label stacking enables the representation of complex non-linear multicast trees through nested path structures, where outer labels represent higher-level tree branches and inner labels represent subordinate branches, eliminating the need for packet duplication at branching points.
2Adaptability or versatility
If multicast forwarding states are installed on routers to build distribution trees, then multicast delivery is achieved, but scalability issues arise due to difficulty in aggregating forwarding states
Solution Approach 1:
The patent makes LSPs universal by enabling them to serve multiple purposes: they function as both unicast paths and multicast distribution tree segments. A single LSP can be shared by multiple multicast groups through the hierarchical label stacking mechanism, where the same LSP appears at different levels of nested label stacks for different groups, thereby aggregating forwarding states and reducing router complexity.
Solution Approach 2:
The patent implements nesting of LSPs within LSPs through hierarchical label stacking, where smaller LSPs (representing subtree segments) are nested within larger LSPs (representing parent tree segments). This nesting allows compact representation of complex multicast trees and enables state aggregation, as the same nested LSP structure can serve multiple multicast groups with different membership patterns.
3Productivity
If new operations popN and copy&pop are introduced on the label stack, then efficient processing of multicast distribution trees is achieved, but MPLS operation complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and pre-configuring the hierarchical label stacks and associated LSPs before multicast traffic arrives. The network operator or control system establishes the complete nested LSP structure in advance, so that when multicast packets arrive, routers simply follow the pre-configured path indicated by the label stack without performing complex real-time decisions, thus improving processing efficiency while managing operational complexity.
Solution Approach 2:
The patent uses copying in the copy&pop operation where a packet is copied to follow different LSP branches at a branching point. Instead of complex stateful forwarding decisions, the router creates a copy of the packet for each required destination branch and pops the appropriate label from each copy's label stack, simplifying the forwarding logic while efficiently handling non-linear multicast distribution.
Data Source
AI summary
Source routed multicast LSP is described herein. In one embodiment, when a first node receives a first packet having a label stack including a plurality of labels compatible with MPLS (multi-protocol label switching), in response to a first label on a top of the label stack, the first packet is duplicated into a second packet. In addition, at least two labels are popped from the top of the label stack of the second packet forming a third packet. Thereafter, the first and third packets are processed based on a label on the top of the label stack of the first and third packets respectively. Other methods and apparatuses are also described.