Switch Line Card Interoperation with Programmable Line Card
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Solution Overview
Problem
Current packet forwarding devices face challenges in efficiently interoperating between switch line cards and programmable line cards, particularly in handling various service interfaces and avoiding repeated Layer 2 encapsulation, which affects forwarding processes and efficiency.
Innovation Solution
The implementation of pseudo-adjacency table entries and pseudo-egress interface entries by the switch chip to provide necessary indices to programmable line cards, allowing them to perform correct Layer 2 encapsulation, and the use of inter-board forwarding headers to facilitate communication between switch and programmable line cards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switch line card and programmable line card are deployed simultaneously to provide large-capacity access and various service interfaces, then the functionality and versatility of the packet forwarding device is improved, but the complexity of interoperating between different line card types increases
Solution Approach 1:
The patent introduces pseudo-adjacency table entries and pseudo-egress interface entries as intermediary structures that mediate between switch line cards and programmable line cards. These pseudo-entries act as translators that enable switch line cards to communicate forwarding information to programmable line cards without requiring direct complex interaction between the different card types, thus reducing interoperation complexity while maintaining versatility
Solution Approach 2:
The patent creates a universal forwarding mechanism that works across both switch line cards and programmable line cards through standardized pseudo-entries. The pseudo-adjacency table entries and pseudo-egress interface entries serve multiple functions: they provide forwarding information, indicate card types, and enable Layer 2 encapsulation across different line card types, thereby simplifying the overall system architecture
2Productivity
If traditional forwarding processes are used between switch and programmable line cards, then packet forwarding can be achieved, but repeated Layer 2 encapsulation occurs which reduces forwarding efficiency
Solution Approach 1:
The patent performs preliminary action by pre-configuring pseudo-adjacency table entries and pseudo-egress interface entries in the switch line card before forwarding packets to programmable line cards. These pre-configured entries contain all necessary forwarding information and encapsulation parameters, allowing the programmable line card to process packets directly without requiring repeated Layer 2 encapsulation, thus improving forwarding efficiency and reducing processing overhead
Solution Approach 2:
The patent extracts the encapsulation function from the traditional forwarding process by using pseudo-egress interface entries that carry encapsulation information separately. This allows the programmable line card to receive packets with already-prepared encapsulation parameters and apply them directly, eliminating the need for repeated encapsulation operations and reducing processing overhead
Data Source
AI summary
When needing to forward a packet from a switch line card to a programmable line card, the switch line card may encapsulate a pseudo-Layer 2 header for the packet based on uplink forwarding process of the switch line card. The pseudo-Layer 2 header may carry an adjacency table index and an egress interface table index which is used by the programmable line card. Correspondingly, the programmable line card may obtain the adjacency table index and the egress interface table index from the pseudo-Layer 2 header of the packet, and then may re-encapsulate a real Layer 2 header for the packet based on downlink forwarding process of the programmable line card, and transmit the packet through a corresponding egress interface.