SD-WAN Multicast Forwarding With BIER to Cut Table Convergence Delay
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Solution Overview
Problem
In software-defined wide area networks (SD-WAN), the large-scale deployment of multicast services leads to a sharp increase in the number of multicast distribution trees and multicast table entries, causing slow convergence and affecting normal network operation.
Innovation Solution
Deploy Bit Index Explicit Replication (BIER) capability on site devices in SD-WAN, using BIER headers to indicate destination nodes and forwarding multicast packets through SD-WAN tunnels, eliminating the need for multicast distribution trees and reducing multicast table entries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PIM protocol is deployed on all CPEs to implement multicast service, then multicast service can be provided, but the quantity of multicast distribution trees and multicast table entries increases sharply, causing slow convergence
Solution Approach 1:
The patent extracts the multicast routing function from intermediate network devices and concentrates it on the BIER ingress device. By using BIER headers with bit strings to directly identify destination nodes, the patent eliminates the need for intermediate devices to maintain multicast distribution trees and table entries, thus resolving the contradiction between service reliability and device complexity
Solution Approach 2:
The patent introduces BIER headers as an intermediary mechanism between the multicast source and destination nodes. These headers contain bit strings that directly encode destination node identifiers, allowing packets to be forwarded without requiring intermediate devices to understand or maintain multicast state, thereby reducing complexity while maintaining service reliability
2Reliability
If PIM protocol is deployed on all CPEs to implement multicast service, then multicast service can be provided, but convergence speed decreases due to large quantity of multicast table entries
Solution Approach 1:
The patent removes multicast routing state maintenance from intermediate network devices entirely. By using BIER headers that directly identify destination nodes through bit strings, the system eliminates the need for intermediate devices to store and update multicast table entries, thus achieving fast convergence while maintaining service reliability
Solution Approach 2:
The patent uses bit string copies in BIER headers to represent destination node sets. Instead of maintaining complex multicast distribution trees, the system simply copies and forwards packets with updated bit strings that indicate which destination nodes should receive the data, enabling rapid convergence without sacrificing service reliability
Data Source
AI summary
A multicast communication method is applied to a software-defined wide area network SD-WAN. In the multicast communication method, a bit index explicit replication (Bit Index Explicit Replication, BIER) capability is deployed on site devices in the SD-WAN, a BIER header in a multicast packet indicates a site device that a multicast packet needs to pass through, and no multicast distribution tree need to be constructed. In addition, the multicast packet is forwarded through an SD-WAN tunnel between site devices, and an intermediate node does not need to sense a multicast service, to reduce a quantity of multicast table entries on a network device and accelerate convergence of the multicast table entries, so that normal running of the multicast service is ensured.