BIER Multicast Forwarding via Independent Nexthop Lookup
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Solution Overview
Problem
Existing BIER multicast packet forwarding technologies face scalability issues due to the need to send full-size BitStrings in headers, which is not efficient, especially when only a small subset of egress routers need to receive the packet.
Innovation Solution
Implement a method where a packet switching device receives a multicast packet with a list of nodes to be forwarded, performs independent lookup operations in a forwarding data structure to identify nexthop nodes, and sends a single copy of the packet to each nexthop node, with the packet containing a second list of nodes to be forwarded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If full-size BitStrings are sent in packet headers to represent all egress routers, then complete multicast routing information is provided, but network bandwidth is wasted when only a small subset of egress routers need to receive the packet
Solution Approach 1:
The patent extracts only the necessary subset of egress router identifiers from the full BitString and includes only those in the packet header. The ingress router determines which egress routers actually need to receive the multicast packet and encodes only those specific identifiers, removing unnecessary data from the header while preserving complete routing information for the required destinations.
2Reliability
If multiple copies of multicast packets are sent to different nexthop nodes, then all destination nodes receive the packet, but the number of packet copies increases network traffic and reduces scalability
Solution Approach 1:
The patent segments the multicast packet distribution by creating separate unicast transmissions to each nexthop node identified from the filtered egress router list. Instead of sending one packet to multiple destinations, the system segments the delivery into individual targeted transmissions, each containing the optimized header with only the relevant subset of egress router identifiers for that specific nexthop path.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
In embodiments, multicast packets including, but not limited to, Bit Index Explicit Replication (BIER) multicast packets, are forwarded in a network. An independent lookup operation is performed on each destination node identified in the received packet to determine a nexthop to which to forward a copy of the packet. Typically, some or possibly all of these lookup operations are performed in parallel, in contrast to the sequential lookup and bit masking operations of previous BIER packet forwarding specifications and implementations. In embodiments, the selection of a nexthop for a destination node is made from a set of two or more nexthop nodes on different Equal-Cost MultiPaths (ECMPs). In embodiments, compact data structures are used in determining how to forward the received multicast packet, with these compact data structures providing requisite forwarding information without allocating space to unassigned destination nodes.