IB-PBB Switch Frame Forwarding via Segmented MAC Lookup
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Solution Overview
Problem
Provider Backbone Bridges (PBBs) with both instance and backbone components (IB-PBBs) require two expensive and burdensome MAC lookup operations due to the large number of MAC addresses in the network, which affects processing efficiency.
Innovation Solution
Implementing a method where frames are forwarded based on either a customer space (C-space) lookup operation for customer instance ports or a backbone space (B-space) lookup operation for provider backbone ports, reducing the need for dual MAC lookups by determining whether frames are local or transient, thereby optimizing forwarding operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two MAC lookup operations are performed for each frame (one for B-MACs and another for C-MACs), then forwarding accuracy is maintained, but processing efficiency deteriorates and operational complexity increases
Solution Approach 1:
The patent segments the forwarding decision process into two distinct paths: local frame forwarding (using only C-space lookup) and transient frame forwarding (using only B-space lookup). This segmentation allows each path to use a single optimized lookup operation rather than requiring both lookups, thereby resolving the contradiction between maintaining forwarding accuracy and improving processing efficiency.
Solution Approach 2:
The patent performs a preliminary determination of whether a frame is local or transient before executing the MAC lookup operations. This preliminary action enables the system to select the appropriate single lookup path in advance, avoiding the need to perform both lookups and thus improving processing efficiency while maintaining forwarding accuracy.
2Reliability
If two MAC lookup operations are performed for each frame, then complete forwarding control is achieved, but device complexity increases due to the large number of MAC addresses
Solution Approach 1:
The patent divides the forwarding control mechanism into separate local and transient frame handling paths. Each path has its own simplified lookup logic (C-space only for local, B-space only for transient), reducing the operational complexity compared to the traditional approach that requires both lookups for all frames, while maintaining complete forwarding control through the preliminary frame type determination.
3Measurement precision
If dual MAC lookups are performed, then accurate frame routing is ensured, but throughput decreases due to the expensive and burdensome nature of the operations
Solution Approach 1:
The patent implements a preliminary frame type determination step that classifies frames as either local or transient before routing. This preliminary action enables subsequent single lookup operations to be performed, significantly reducing the computational burden compared to dual lookups and thereby increasing throughput while maintaining routing accuracy through the optimized lookup paths.
Data Source
AI summary
In one embodiment, when a frame is directed to one or more customer instance ports (CIPs) of a switch having received the frame, the frame (a “local frame”) may be forwarded on the one or more CIPs based on only a customer space (C-space) lookup operation. Also, if the frame is not directed to any CIPs of the switch, the frame (a “transient frame”) may be forwarded on at least one or more provider backbone ports (PBPs) of the switch based on only a backbone space (B-space) lookup operation. For example, a unicast frame may be forwarded based on whether the frame terminates at the switch having received the frame (to a CIP of the switch), while a multicast frame may be forwarded based on determining whether an instance service identifier (I-SID) of the frame maps to a local VLAN ID (L-VID) at the switch (to any CIPs servicing that L-VID).