Multicast Forwarding Across Autonomous Systems via BFR ID Translation
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Solution Overview
Problem
Multicast forwarding across Autonomous Systems (ASs) is hindered by Bit Forwarding Router Identifier (BFR ID) conflicts in different Bit Indexed Explicit Replication (BIER) domains, which prevents seamless inter-domain forwarding.
Innovation Solution
Deploying a network device as both a Bit Forwarding Egress Router (BFER) in one BIER domain and a Bit Forwarding Ingress Router (BFIR) in another, allowing for the modification and conversion of BFR IDs within multicast join packets to resolve conflicts and enable seamless forwarding across ASs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If BIER domains are deployed in different ASs with pre-configured BFR IDs, then each AS can independently perform multicast forwarding within its domain, but BFR ID conflicts occur when attempting multicast forwarding across ASs
Solution Approach 1:
The patent segments the BIER domain scope by introducing domain-specific BFR ID spaces. Each AS maintains its own BFR ID configuration independently, preventing conflicts when forwarding across AS boundaries. The segmentation allows intra-AS multicast to continue using original BFR IDs while inter-AS multicast uses modified global BFR IDs.
Solution Approach 2:
The patent modifies the BFR ID parameter itself by introducing a domain identification component. When a BFR ID needs to be used across AS boundaries, it is transformed to include domain-specific information, changing its parameter structure from a simple router identifier to a globally unique identifier that incorporates AS domain context.
2Ease of manufacture
If BFR IDs are pre-configured in different ASs, then device deployment is simplified, but BFR ID conflicts prevent seamless inter-domain multicast forwarding
Solution Approach 1:
The patent introduces ASBR (Autonomous System Border Router) as an intermediary device that handles BFR ID translation between different AS domains. The ASBR receives multicast join packets, modifies the BFR IDs to resolve conflicts, and forwards them appropriately. This intermediary approach maintains deployment simplicity while enabling seamless inter-domain operations.
Solution Approach 2:
The patent performs preliminary BFR ID modification at the ASBR before packets are forwarded across domain boundaries. By pre-modifying the BFR IDs in join packets and establishing forwarding relationships in advance, the system avoids conflicts during actual multicast forwarding operations, maintaining both deployment simplicity and operational ease.
3Reliability
If multicast forwarding is limited to within a single BIER domain, then BFR ID conflicts are avoided, but multicast services cannot be extended across multiple ASs
Solution Approach 1:
The patent implements a nested structure where multiple BIER domains (each with its own BFR ID space) are contained within a larger inter-AS multicast framework. Each AS maintains its independent BIER domain with stable internal BFR IDs, while the outer framework enables cross-domain forwarding by translating and coordinating these nested BFR ID spaces through ASBRs.
Data Source
AI summary
A multicast forwarding method comprises: establishing, by a network device, BIER multicast forwarding information for joining a target multicast group according to a multicast join packet initiated by a multicast receiver connected to a second edge node in a second AS, the second edge node serving as a BFER in a second BIER domain, the target multicast group being a multicast group to which a multicast source connected to a first edge node in a first AS belongs, and the first edge node serving as a BFIR in a first BIER domain; and modifying a BFR ID of the second edge node carried in the multicast join packet into a first BFR ID, and continuing to send the multicast join packet to the first edge node, wherein the first BFR ID is a BFR ID configured when the network device is deployed as the BFER in the first BIER domain.