Virtual Interfaces for Multicast Reverse Path Forwarding in MPLS
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Solution Overview
Problem
MPLS networks do not support standard multicast routing protocols like reverse path forwarding, and upgrading provider core networks to handle IPv6 or point-to-multipoint LSPs is not feasible, making it difficult to transmit multicast packets across geographically diverse networks.
Innovation Solution
Implementing virtual interfaces at the egress edge router to associate labels with multicast data streams, allowing reverse path forwarding checks without requiring core network configuration for multicast protocols, enabling the use of point-to-point LSPs to facilitate multicast routing across MPLS networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If standard multicast routing protocols are used in MPLS networks, then multicast transmission can be supported, but core network upgrades are required which are not feasible
Solution Approach 1:
The solution segments the multicast routing functionality by separating it from the core MPLS network. Virtual interfaces are created at the egress router to handle RPF checks locally, while the core network continues to use simple point-to-point LSPs without multicast protocol requirements. This segmentation allows multicast support without upgrading core network devices.
Solution Approach 2:
Virtual interfaces act as an intermediary mechanism between the MPLS core network and multicast routing requirements. The virtual interface at the egress router mediates the RPF check process, allowing multicast packets to be validated without requiring the core network to understand or support multicast protocols.
2Adaptability or versatility
If point-to-multipoint LSPs are implemented, then multicast routing is enabled, but compatibility with existing MPLS infrastructure is lost
Solution Approach 1:
Instead of modifying the LSP type to support multicast (point-to-multipoint), the solution inverts the approach by using standard point-to-point LSPs and implementing multicast functionality through virtual interfaces at the egress router. This inversion maintains compatibility with existing MPLS infrastructure while achieving multicast capability.
3Device complexity
If reverse path forwarding checks are performed without virtual interfaces, then routing validation is simplified, but loop-free distribution cannot be ensured
Solution Approach 1:
The solution creates a virtual copy of the upstream interface at the egress router. This virtual interface replicates the characteristics needed for RPF checks without requiring physical interface modifications. The virtual interface allows the router to perform validation against the expected upstream path while maintaining the simplicity of point-to-point LSPs in the core network.
Data Source
AI summary
A mechanism is provided in which multicast reverse path forwarding can be performed at a provider network egress edge router wherein core routers of the provider network are not configured to support multicast protocols or point-to-multipoint LSPs. An embodiment of the present invention provides for the creation of virtual interfaces in the egress edge router element during configuration of a multicast connection in response to a subscriber request. A virtual interface will be associated with an upstream ingress edge router element and that ingress edge router element is provided a label associated with the virtual interface. Such a label can then be included in datastream packets transmitted through the provider network and be used by reverse path forward checking at the egress edge router element to ascertain whether the multicast datastream is being received by the correct upstream interface.