Policy-Based Redirection for IP Multicast Scaling
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Solution Overview
Problem
Conventional IP multicasting faces challenges in scaling due to limitations in packet forwarding devices, where FDB resources become bottlenecks, leading to insertion failures and increased slowpath processing, even with advanced hashing algorithms, resulting in hash bucket collisions before the IPMC FDB is fully utilized.
Innovation Solution
Implementing policy-based redirection by creating a packet redirection rule when insertion into the IPMC FDB fails, allowing the system to redirect IP multicast streams using a separate PBR ACR data structure and IPMC egress port data structure, thereby avoiding slowpath processing and enhancing multicast scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional IP multicast forwarding is implemented using IPMC FDB, then multicast packet forwarding can be performed, but FDB resources become a bottleneck leading to insertion failures and limited scaling
Solution Approach 1:
The patent segments the multicast forwarding function by separating it from the traditional IPMC FDB structure. Instead of relying solely on FDB entries for all multicast forwarding decisions, the system divides the forwarding path into segments: some handled by FDB lookups and others by policy-based redirection rules. This segmentation allows the system to bypass FDB insertion limitations and achieve better scaling.
Solution Approach 2:
The patent introduces policy-based redirection (PBR) as an intermediary mechanism between packet reception and traditional FDB-based forwarding. When FDB insertion fails or is not optimal, PBR rules act as mediators to redirect packets through alternative paths using external lookup tables. This intermediary approach resolves the bottleneck by providing multiple forwarding pathways that don't depend on limited FDB resources.
2Measurement precision
If advanced hashing algorithms are used for FDB entry insertion, then packet distribution is improved, but hash bucket collisions still occur resulting in insertion failures before FDB is fully utilized
Solution Approach 1:
Policy-based redirection rules serve as an intermediary that handles packets which would otherwise fail FDB insertion due to hash bucket collisions. Instead of forcing all packets through the hashing mechanism, the system uses PBR as a mediator to redirect qualifying packets through alternative forwarding paths, thereby bypassing the collision problem entirely while maintaining good packet distribution where FDB insertion succeeds.
3Reliability
If FDB entry insertion failure occurs, then slowpath processing is performed, but this increases processing time and reduces forwarding performance
Solution Approach 1:
The system performs preliminary actions by pre-configuring policy-based redirection rules that can handle multicast forwarding scenarios. Instead of waiting for FDB insertion failure and then performing slowpath processing, the PBR rules are already in place to immediately redirect packets that don't match FDB entries or for which insertion fails. This preliminary preparation eliminates the need for time-consuming slowpath processing while maintaining complete forwarding functionality.
Data Source
AI summary
Methods, systems, and computer readable media for improved multicast scaling through policy based redirection are disclosed. According to one method, a packet belonging to an Internet protocol multicast (IPMC) stream is received, where the packet includes packet routing information. A lookup is performed in a IPMC forwarding database (FDB) and, in response to failing to locate an entry in the IPMC FDB, an attempt is made to insert the packet routing information in the IPMC FDB. In response to failing to insert the packet routing information in the IPMC FDB, a packet redirection rule is created based on the packet forwarding information.