BIER Multicast PMTU Discovery via Targeted Probe Segmentation
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Solution Overview
Problem
Current PMTUD mechanisms are inefficient for multicast traffic in networks using bit indexed explicit replication (BIER) as they require flooding probe packets across all multicast distribution paths until the last egress responds, leading to high overhead and resource consumption.
Innovation Solution
The method involves selecting specific egress BFRs in the BIER domain, generating probe packets with an initial MTU, and iteratively reducing packet size upon MTU failures, targeting only identified downstream BFRs for subsequent probes, thereby reducing unnecessary packet traffic and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If probe packets are flooded through the whole set of multicast distribution paths, then PMTU discovery can be performed for all egress nodes, but the amount of probe packet traffic and resource consumption increases significantly
Solution Approach 1:
The patent segments the multicast distribution paths by identifying specific egress BFRs that need PMTU discovery. Instead of flooding probe packets to all possible egress nodes, the system divides the discovery process into targeted segments based on the Bit Mask Set (BMS) information, sending probe packets only to necessary egress BFRs or groups of BFERs.
Solution Approach 2:
The patent applies partial action by performing PMTU discovery only for the subset of egress BFRs that are actually needed for the multicast distribution, rather than exhaustively discovering PMTU for all possible egress nodes in the BIER domain. This is achieved by using the BMS to identify and target only the relevant egress points.
2Loss of information
If probe packets are sent to all egress BFERs in the multicast distribution, then complete PMTU information is obtained, but network overhead and processing time increase
Solution Approach 1:
The patent performs preliminary action by using the Bit Mask Set (BMS) information available in the multicast distribution setup to pre-identify which egress BFRs need PMTU discovery. This preliminary identification based on BMS allows the system to skip unnecessary egress nodes and directly target the relevant ones, reducing the overall discovery time while maintaining information completeness.
3Reliability
If probe packet flooding is used for multicast PMTU discovery, then all path MTUs are discovered, but scalability to large BIER domains is limited
Solution Approach 1:
The patent applies local quality by making the PMTU discovery process adaptive to local network conditions and requirements. Each ingress BFR uses its specific BMS to determine which egress BFRs are relevant for its multicast distributions, allowing tailored and efficient discovery processes for different parts of the BIER domain rather than a one-size-fits-all flooding approach.
Data Source
AI summary
A method and system provides for path maximum transmission unit (PMTU) discovery (PMTUD) for a multicast distribution implemented in a network using bit indexed explicit replication (BIER) architecture. The network has a set of bit forwarding routers (BFRs) that form a BIER domain including at least one ingress BFR (BFIR) and a set of egress BFRs (BFERs). The method improves efficiency of the PMTUD by limiting probe packet traffic. The method includes selecting a BFER from the set of BFERs in the BIER domain to be processed, generating a probe packet to the selected BFER using a current MTU, sending the probe packet to the selected BFER, and updating the current MTU and adding BFERs identified by a response to the probe packet to the set of BFERs in the BIER domain to be processed.