Stateless Multicasting via Unicast TE-LSPs

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Solution Overview

Problem

Stateful traffic engineered MPLS multicasting faces scalability issues due to the need for centralized controllers and high overhead in label stacks, which limits the number of supported TE-MDTs in networks, especially as the number of routers and egress routers increases.

Innovation Solution

Implementing stateless MPLS multicasting using unicast TE-LSPs that satisfy quality-of-service (QoS) criteria, where an ingress router selects a subset of unicast paths to egress routers, eliminating the need for a centralized controller and reducing label stack overhead by encoding only the necessary unicast paths in the label stack.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If stateful traffic engineered MPLS multicasting is implemented, then QoS-aware multicast delivery is achieved, but device complexity and scalability deteriorate due to centralized controller requirements and high label stack overhead

Engineering Contradiction:

ImproveQoS-aware multicast deliveryVSAvoidcentralized controller overhead

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and removes the centralized controller component from the stateful MPLS multicasting architecture. Instead of requiring a centralized controller to manage TE-MDT states, the invention implements stateless MPLS multicasting where the ingress router independently selects unicast TE-LSPs that satisfy QoS criteria, eliminating the scalability limitations imposed by centralized control while maintaining QoS-aware multicast delivery

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent segments the multicast distribution tree into multiple unicast TE-LSPs. Rather than maintaining a single stateful TE-MDT that requires centralized coordination, the invention divides the multicast traffic into separate unicast paths, each with its own label stack. This segmentation allows parallel processing and eliminates the single point of complexity represented by the centralized controller

Inventive Principle:

Principle #1Segmentation

2Reliability

If stateful traffic engineered MPLS multicasting is implemented, then QoS-aware multicast delivery is achieved, but productivity deteriorates due to high label stack overhead limiting the number of supported TE-MDTs

Engineering Contradiction:

ImproveQoS-aware multicast deliveryVSAvoidnumber of supported TE-MDTs

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent uses copying by creating multiple unicast TE-LSPs that replicate the QoS characteristics of a single TE-MDT. Instead of maintaining one complex stateful multicast path with large label stacks, the invention copies the traffic flow across multiple simpler unicast paths, each with smaller label stacks. This copying approach increases the total number of supported TE-MDTs by distributing the label stack overhead across multiple independent unicast paths

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent applies partial action by selecting only a subset of available unicast TE-LSPs that satisfy the QoS criteria for each multicast flow. Rather than maintaining all possible TE-MDTs with full label stacks, the ingress router selectively activates only the necessary unicast paths, reducing overall label stack overhead and increasing the number of simultaneously supported TE-MDTs

Inventive Principle:

Principle #16Partial or excessive action

3Reliability

If stateful traffic engineered MPLS multicasting is implemented, then QoS-aware multicast delivery is achieved, but loss of time increases due to centralized controller coordination overhead

Engineering Contradiction:

ImproveQoS-aware multicast deliveryVSAvoidprocessing latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements self-service by enabling the ingress router to independently select and manage unicast TE-LSPs without requiring centralized controller coordination. The ingress router autonomously evaluates QoS criteria and selects appropriate unicast paths, eliminating the time-consuming coordination overhead with centralized controllers. This self-service approach significantly reduces processing latency while maintaining QoS-aware multicast delivery

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent applies preliminary action by pre-establishing unicast TE-LSPs that satisfy QoS criteria before multicast traffic needs to be delivered. The ingress router maintains a pool of pre-validated unicast paths with known QoS characteristics, allowing immediate selection and activation when multicast flows need to be established. This preliminary preparation eliminates the time required for real-time centralized controller coordination and path computation

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11706136B2Stateless multicasting over traffic engineered unicast tunnels

Publication Date: 2023.07.18 NOKIA SOLUTIONS & NETWORKS OY

AI summary

A software defined networking (SDN) controller or routers in a network determine unicast paths from an ingress router to egress routers from the network based on quality-of-service (QoS) metrics for links between routers of the network. A subset of the unicast paths is associated with a multicast flow based on one or more QoS criteria for the multicast flow. A router pushes a label stack onto a packet of the multicast flow. The label stack includes labels that identify the subset of the unicast paths. The packet including the label stack is multicast through the network to the egress routers. Routers that receive the multicast packet selectively modify the label stack in the packet based on the labels that identify the subset of the unicast paths. The routers selectively forward the packet based on the labels.