Multicast Tree Identifier Encoding in TRILL Networks
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Solution Overview
Problem
Supporting multiple multicast trees in TRILL networks is resource-intensive, as existing approaches require significant resources at each switch and can limit the number of multicast groups that can be supported.
Innovation Solution
A system determines an internal multicast group identifier based on the source address, multicast address, and multicast tree identifier, allowing for efficient forwarding of multicast packets across multiple trees by combining bits from these fields to identify egress ports, and encapsulating packets in a TRILL header for network virtualization and partitioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple multicast trees are supported for load balancing and failure recovery, then network reliability and bandwidth utilization are improved, but resource requirements at each switch increase significantly
Solution Approach 1:
The patent segments the multicast group identifier into multiple components: a high-order portion derived from the multicast address and a low-order portion derived from the source address. This segmentation allows switches to use only the high-order portion for forwarding decisions, reducing the state information each switch must maintain while still supporting multiple multicast trees through the low-order portion that identifies different trees for the same group.
Solution Approach 2:
The patent introduces a new dimension to multicast addressing by utilizing bits from the source address field (which traditionally serves a different purpose) to encode tree identification information. This dimensional transformation allows multiple multicast trees to be distinguished without requiring additional address space or increasing switch state requirements.
2Productivity
If multiple multicast trees are supported for load balancing, then bandwidth utilization is improved, but the number of multicast groups that can be supported is limited by switch resources
Solution Approach 1:
The patent makes the source address field serve a dual function: its traditional role in identifying the packet source and an additional role in encoding multicast tree identification information. This multi-functionality allows the same field to support both unicast and multicast operations while enabling multiple multicast trees without requiring additional dedicated fields or increasing switch resource requirements.
Solution Approach 2:
The patent merges the identification of multicast groups and multicast trees into a unified addressing scheme. By combining the high-order bits from the multicast address with low-order bits from the source address, the patent creates a composite identifier that simultaneously identifies both the target group and the specific tree, allowing switches to handle multiple trees efficiently without increasing their state requirements.
Data Source
AI summary
Systems and techniques for supporting multiple multicast trees are described. Some embodiments provide a system that determines an internal multicast group identifier based on a source address, a multicast address, and a multicast tree identifier field associated with a multicast packet. The system can then forward the multicast packet based on the internal multicast group identifier. Specifically, the system can determine a first set of bits based on the source address and the multicast address of the multicast packet. The system can determine a second set of bits based on the multicast tree identifier field of the multicast packet. Next, the system can combine the first set of bits and the second set of bits to obtain the internal multicast group identifier. In some embodiments, the scope of an internal virtual network identifier does not extend beyond a switch or a forwarding module within a switch.