Multicast Packet Routing in Link Aggregation Groups
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Solution Overview
Problem
Routing multicast packets in network devices can lead to multicast loops or storms, consuming excessive bandwidth due to the transmission of multiple copies of the same packet to the same location, especially in Link Aggregation Groups (LAGs).
Innovation Solution
Implementing a system that uses a routing sequencer and scheduler to determine multicast group membership and LAG vectors, filtering out the receiving port from multicast packets to prevent loops, and sending packets only to identified ports within the multicast vector, thereby avoiding unnecessary transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multicast packets are transmitted to all ports within a LAG, then complete multicast delivery is achieved, but multicast loops or storms occur consuming excessive bandwidth
Solution Approach 1:
The patent segments the LAG ports into two categories: receiving ports and non-receiving ports. The routing sequencer identifies which port received the multicast packet and segments the forwarding action to exclude only the receiving port from the multicast transmission, while still delivering to all other LAG ports. This segmentation prevents loops while maintaining complete delivery to intended destinations.
Solution Approach 2:
The patent extracts the receiving port from the set of ports that would otherwise receive the multicast packet. By identifying and removing the receiving port from the forwarding list, the system prevents the packet from being sent back to its source, thereby avoiding multicast loops and storms while still delivering to all other necessary ports.
2Ease of operation
If multicast packets are sent from the same port that received the packet, then packet forwarding is simplified, but multicast storms occur
Solution Approach 1:
The patent applies preliminary anti-action by proactively identifying and preventing the harmful action before it occurs. The routing sequencer examines the incoming multicast packet, identifies the receiving port, and pre-empts the creation of a loop by excluding this port from the forwarding decision. This prevents the multicast storm from occurring in the first place rather than reacting to it afterward.
Solution Approach 2:
The patent implements feedback by having the routing sequencer monitor which port received the multicast packet and use this information to adjust the forwarding behavior. The system feeds back the receiving port identity to the scheduling logic, which then modifies the transmission list to exclude this port, creating a closed-loop control that prevents multicast storms.
3Reliability
If multiple copies of the same packet are transmitted to the same location, then redundancy is provided, but network bandwidth is wasted
Solution Approach 1:
The patent segments the set of destination ports by identifying which ports are part of the LAG and which are not. It then segments the transmission action to send only one copy of the packet to the LAG group (to the non-receiving ports) while providing separate unicast transmissions to individual destinations outside the LAG. This eliminates redundant multicast copies within the LAG while maintaining necessary redundancy for external destinations.
Solution Approach 2:
The patent applies different transmission strategies to different destination groups: multicast transmission to LAG ports (excluding the receiving port) and unicast transmission to non-LAG ports. This local quality differentiation optimizes bandwidth usage by applying the appropriate transmission method to each destination type, avoiding unnecessary multicast copying within the LAG while maintaining reliable delivery to external destinations.
Data Source
AI summary
Method and system for a network device are provided. The device includes a port for receiving a multicast packet and a multicast data structure for maintaining information regarding a multicast group to which the multicast packet is to be sent. When the port is a part of a link aggregation group (LAG), then any port that is a member of the LAG is removed from the multicast group such that the multicast packet is not sent to any member of the LAG.