Multicast Routing in Network-on-Chip Interconnects
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Solution Overview
Problem
Current Network-on-Chip (NoC) interconnects face challenges in efficiently supporting multicast messages due to increased channel dependencies, complex deadlock avoidance, and high overhead in determining routes and storing information, leading to limited multicast support and quality of service issues.
Innovation Solution
The implementation of multicast trees in NoC topology, where nodes with filters assess and forward messages based on intended destination nodes, and the use of multiple trees to optimize routing based on parameters like distance, latency, and bandwidth, allows for efficient multicast message delivery and response aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional routing methods are used in NoC interconnect, then routing simplicity is maintained, but multicast support efficiency deteriorates due to increased channel dependencies and complex deadlock avoidance
Solution Approach 1:
The patent segments the multicast routing problem by introducing virtual channels that separate control traffic from data traffic, and by dividing the routing decision process into source node route determination and intermediate node forwarding operations. This segmentation reduces channel dependencies and simplifies deadlock avoidance mechanisms.
Solution Approach 2:
The patent introduces virtual channels as intermediary resources that mediate between physical channels and multicast groups. These virtual channels act as buffers and routing decision points, reducing direct dependencies between physical channels and simplifying the overall routing control structure.
2Ease of manufacture
If deterministic routing is used, then packet ordering is maintained and hardware implementation is simplified, but load balancing across path diversities deteriorates
Solution Approach 1:
The patent introduces dynamic route selection at the source node for multicast traffic, allowing the system to adaptively choose from multiple available paths based on current network conditions. This dynamic approach enables load balancing across path diversities while maintaining deterministic forwarding behavior at intermediate nodes for hardware simplicity.
3Loss of time
If shortest path routing is used, then latency is minimized, but network level deadlocks may occur due to lack of path diversity
Solution Approach 1:
The patent adds the dimension of virtual channels to the physical network topology, creating a multi-dimensional routing space. This allows shortest path routing to be maintained in the physical dimension for low latency, while the virtual channel dimension provides path diversity and deadlock avoidance mechanisms.
4Device complexity
If multicast messages are transmitted using traditional unicast replication, then routing infrastructure is simple, but channel bandwidth consumption increases
Solution Approach 1:
The patent merges multiple unicast transmissions into a single multicast transmission by introducing multicast group concepts and virtual channels. Multiple destination nodes share the same virtual channel resources, combining their bandwidth requirements and reducing overall channel bandwidth consumption compared to separate unicast transmissions.
Data Source
AI summary
Example implementations are directed to more efficiently delivering a multicast message to multiple destination components from a source component. Multicast environment is achieved with transmission of a single message from a source component, which gets replicated in the NoC during routing towards the destination components indicated in the message. Example implementations further relate to an efficient way of implementing multicast in any given NoC topology, wherein one or more multicast trees in the given NoC topology are formed and one of these trees are used for routing a multicast message to its intended destination components mentioned therein.