SPB Network UNI Multi-Homing via Egress Port Masks
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Solution Overview
Problem
Conventional multi-homing mechanisms for SPB networks, such as SMLT and stacking, face limitations including redundancy of only two nodes, requirement of dedicated intra-cluster links, undefined forwarding behaviors, and potential network instability due to segmentation of intra-cluster links.
Innovation Solution
The solution involves determining a set of UNI nodes based on BMAC-DA/I-SID for multicast packets within a transport network, applying a separate Egress Port Mask for each B-VLAN to ensure only one node forwards multicast packets, and using a private clustering protocol to manage port state information, allowing for active/active traffic forwarding and continuous management access across multiple nodes without dedicated intra-cluster links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional multi-homing mechanisms (SMLT, stacking) are used, then two-node redundancy is provided, but redundancy beyond two nodes cannot be achieved
Solution Approach 1:
The patent segments the multi-homing function by introducing separate Egress Port Masks for each B-VLAN, allowing different nodes to be selected as forwarding nodes for different VLANs. This enables more than two nodes to participate in multi-homing while maintaining controlled forwarding behavior, thus extending redundancy beyond the two-node limitation of conventional SMLT and stacking mechanisms.
2Reliability
If dedicated intra-cluster links are used, then control plane communication is ensured, but device complexity and network infrastructure requirements increase
Solution Approach 1:
The patent makes the transport network links serve dual purposes: they carry both user data traffic and control plane communication between cluster nodes. By utilizing the same physical infrastructure for multiple functions and employing protocol-based node identification and state information exchange, the patent eliminates the need for dedicated intra-cluster links while maintaining reliable control plane communication.
3Productivity
If multiple nodes forward multicast packets, then traffic distribution is improved, but network loops and duplication occur
Solution Approach 1:
The patent applies different forwarding behaviors to different VLANs by introducing separate Egress Port Masks for each B-VLAN. This allows selective control of which nodes forward multicast packets for each VLAN, enabling traffic distribution across multiple nodes while preventing loops through VLAN-specific forwarding rules. Each VLAN can have its own designated forwarding node(s), eliminating the harmful effects of uncontrolled multi-node forwarding.
4Reliability
If intra-cluster links segment into separate islands, then network resilience is improved, but routing protocol stability deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where cluster nodes exchange state information through the transport network using a private clustering protocol. This continuous feedback loop allows nodes to detect link segmentations and adjust their behavior accordingly, maintaining routing protocol stability even when physical links segment into separate islands. The feedback mechanism ensures that each island recognizes its isolated state and prevents unstable routing behavior.
Data Source
AI summary
A method, apparatus and computer program product for providing multi-homing techniques for SPB networks is presented. A set of UNI nodes that receive multicast packets are determined based on Backbone Media Access Control-Destination Address (BMAC-DA)/I-Tag Service Identifier (I-SID) of received multicast packets for multicast packets within a transport network. A separate Egress Port Mask is determined for each Backbone-Virtual Local Area Network (B-VLAN) of the transport network, wherein the Egress Port Mask is determined such that only one UNI node of the set of UNI nodes forwards said multicast packets. A set of UNI copies of said multicast packets are filtered out by applying the Egress Port Mask, wherein copies that are not in the Egress Port Mask are dropped. Copies of multicast packets that are not dropped are sent out.