Extending LDP for Point-to-Multi-Point Label Switched Paths

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Solution Overview

Problem

Existing protocols for establishing point-to-multi-point (P2MP) Label Switched Paths (LSPs) in computer networks, such as RSVP, face impracticality in VPN networks already using Label Distribution Protocol (LDP and struggle with scalability, especially with a large number of provider edge routers.

Innovation Solution

Extending the Label Distribution Protocol (LDP) to create a P2MP label map message with a forwarding equivalence class (FEC) element that includes a root node address and opaque identifier, allowing LDP to set up P2MP LSPs and enabling destination network devices to initiate setup and teardown, with intermediate devices replicating packets across branches of the LSP.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If RSVP protocol is used to set up P2MP LSPs, then multicast traffic can be transmitted, but the system complexity increases and scalability deteriorates in networks with large number of provider edge routers

Engineering Contradiction:

Improvemulticast traffic transmission capabilityVSAvoidprotocol complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The LDP protocol is extended to perform multiple functions including unicast LSP establishment and P2MP LSP establishment, eliminating the need for separate RSVP protocol infrastructure. The extension adds P2MP-specific FEC elements and label map message formats to the existing LDP framework, allowing a single protocol to handle both unicast and multicast traffic engineering.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Instead of having the source initiate P2MP LSP setup as in traditional RSVP, the destination devices initiate the setup by sending label map messages upstream to the root node. This inversion simplifies the control plane by allowing destinations to directly request multicast service without complex source-side signaling.

Inventive Principle:

Principle #13The other way round (Inversion)

2Adaptability or versatility

If a second label distribution protocol (RSVP) is deployed alongside LDP, then P2MP LSP setup becomes possible, but the device complexity and operational difficulty increase

Engineering Contradiction:

ImproveP2MP LSP setup capabilityVSAvoidprotocol deployment difficulty

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

LDP is enhanced to provide both unicast and P2MP LSP establishment capabilities within a single protocol instance. The extension introduces P2MP-specific FEC elements that can be carried in existing LDP message formats, allowing operators to manage both unicast and multicast LSPs using the same protocol infrastructure and operational procedures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges P2MP LSP establishment functionality into the existing LDP protocol framework by extending FEC elements and message formats. This consolidation eliminates the need for separate RSVP deployment, reducing operational complexity while maintaining full P2MP multicast capability.

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If traditional unicast LSP establishment is used for each destination, then simple point-to-point paths are created, but bandwidth efficiency deteriorates due to duplicate packet transmission

Engineering Contradiction:

Improvepath establishment simplicityVSAvoidbandwidth utilization efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The P2MP LSP is segmented into multiple branches originating from a single root node, with each branch serving one or more destination devices. Intermediate nodes on each branch replicate packets locally rather than forwarding identical copies through the entire path, reducing redundant transmissions and improving bandwidth efficiency while maintaining simple path management.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from traditional one-dimensional point-to-point LSPs to a tree-structured P2MP LSP that operates in multiple dimensions, with a single root node branching out to multiple destinations through intermediate nodes. This dimensional expansion allows efficient multicast delivery by creating shared path segments that serve multiple destinations simultaneously.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS7564803B1Point to multi-point label switched paths with label distribution protocol

Publication Date: 2009.07.21 JUNIPER NETWORKS INC

AI summary

The label distribution protocol (LDP) is extended to set up a point to multi-point (P2MP) label switched path (LSP) across a computer network from a source network device to one or more destination network devices. LDP is extended to create a P2MP label map message containing a label and a P2MP forwarding equivalence class (FEC) element having a root node address and an identifier. The P2MP FEC element may, for example, associate an address of the root node of the P2MP LSP with an opaque identifier. The P2MP FEC element uniquely identifies the P2MP LSP. The P2MP FEC element may be advertised with a label in a P2MP label map message. A source network device or the destination network devices may initiate setup and teardown of the P2MP LSP. The P2MP label map messages may be propagated from the destination network devices to the source network device.