Network Link Group Sub-Link for Broadcast Frame FDB Registration
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Solution Overview
Problem
In multistage network systems using a FAT-Tree topology, broadcast frames, such as ARP request frames, cannot be simultaneously registered in the forwarding databases (FDB) of multiple upper switches due to the configuration of Link Aggregation Groups (LAG) in lower switches, leading to incomplete address registration.
Innovation Solution
A network system with a link group connecting lower and upper switches in a multipoint-to-multipoint relationship, utilizing sub-links for point-to-point and main links for point-to-multipoint logical connections, allows broadcast frames to be transmitted and received by all upper switches, enabling simultaneous registration of source addresses in their FDBs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LAG is configured in the lower switch to bundle ports connected to different upper switches, then transmission and reception of frames between lower switches is shared among multiple upper switches, but source address contained in broadcast frame cannot be simultaneously registered to FDB in multiple upper switches
Solution Approach 1:
The link group is segmented into two distinct logical links: a sub-link for point-to-point communication and a main link for point-to-multipoint communication. This segmentation allows broadcast frames to be transmitted through the sub-link to ensure all upper switches receive them for complete address registration, while unicast frames continue to use the main link for load sharing across multiple upper switches.
Solution Approach 2:
The sub-link acts as an intermediary channel specifically for broadcast frame transmission. By introducing this dedicated communication path, the system ensures that broadcast frames reach all upper switches reliably, solving the address registration problem without affecting the load-sharing capability of the main link.
2Ease of operation
If broadcast frame is transmitted through only one physical link in LAG, then transmission is simplified, but other upper switches cannot receive the broadcast frame for FDB registration
Solution Approach 1:
The communication channels are segmented into sub-link and main link with distinct functions. The sub-link is specifically designated for broadcast frame transmission to all upper switches, ensuring reliable address registration, while the main link handles unicast traffic for load sharing.
Solution Approach 2:
The sub-link serves as a universal channel for all lower switches to transmit broadcast frames to all upper switches. This multi-functional link ensures that regardless of which lower switch sends the broadcast frame, all upper switches can receive it and register the source address in their FDBs.
3Productivity
If ARP request frame is transmitted from any one port belonging to LAG, then transmission is straightforward, but source address can be registered in FDB of only the receiving upper switch
Solution Approach 1:
The sub-link serves as an intermediary channel that ensures broadcast ARP request frames are transmitted to all upper switches. This dedicated path guarantees that the source address in the ARP request frame is registered in the FDB of all upper switches, not just the one that receives the frame through the main link.
Solution Approach 2:
Instead of allowing broadcast frames to be transmitted through any LAG port (as in conventional LAG), the invention inverts the approach by designating specific ports forming a sub-link exclusively for broadcast frame transmission. This inversion ensures systematic delivery to all upper switches.
Data Source
AI summary
A network system includes a plurality of lower switches, a plurality of upper switches, and a link group for interconnecting the plurality of lower switches to the plurality of upper switches in a multipoint-to-multipoint relationship. The link group includes a sub-link for interconnecting the plurality of lower switches to the plurality of upper switches in a point-to-point relationship as one logical link and a main link for interconnecting the plurality of lower switches to the plurality of upper switches in a point-to-multipoint relationship as one logical link. The plurality of lower switches are each set such that a broadcast frame with a broadcast address set as a destination is transmitted to the plurality of upper switches through the sub-link. The plurality of upper switches each receive the broadcast frame and resister a source address contained in the broadcast frame into an FDB of the plurality of upper switches.