Router Preserving Link-Layer Priority for Consistent QoS
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Solution Overview
Problem
Conventional IP routers discard link-layer priority values, making it difficult to maintain consistent Quality of Service (QoS) across different subnets in Ethernet networks, requiring complex mappings and host configuration to preserve priority flow control.
Innovation Solution
A router architecture that copies link-layer priority values from the ingress interface to the egress interface without modification, allowing for consistent QoS across subnets by preserving the Priority Code Point (PCP) values in Ethernet headers, and providing configurable options to set new PCP values based on network-layer priority values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional IP routers discard link-layer priority values, then device complexity is reduced, but Quality of Service consistency across subnets deteriorates
Solution Approach 1:
The patent extracts the link-layer priority value from the link-layer header and preserves it separately through the router. The router extracts this value at the ingress interface and copies it to the egress interface without modification, separating the priority preservation function from the typical packet forwarding operations.
Solution Approach 2:
The router performs preliminary action by copying the link-layer priority value from the ingress interface to the egress interface before the packet is transmitted. This ensures the priority value is preserved and available for QoS enforcement at the egress interface, preventing packet loss and maintaining consistent service levels.
2Reliability
If complex DSCP/PCP mappings are implemented to maintain QoS, then QoS consistency is improved, but device complexity increases
Solution Approach 1:
The patent uses copying to preserve the link-layer priority value directly from the ingress interface to the egress interface without any transformation or mapping. This simple copy operation maintains the original priority value intact, avoiding the need for complex DSCP/PCP mapping tables and configuration.
Solution Approach 2:
Instead of mapping network-layer priority values to link-layer priority values (the conventional approach), the patent inverts the approach by preserving the link-layer priority value through the router unchanged. This inversion eliminates the need for mapping complexity while maintaining QoS consistency.
3Adaptability or versatility
If link-layer priority values are modified based on network-layer priority values, then adaptability is improved, but QoS consistency deteriorates
Solution Approach 1:
The patent introduces dynamics by making the router configurable between two modes: a first configuration that copies the link-layer priority value without modification, and a second configuration that sets a new link-layer priority value based on the network-layer priority value. This allows the system to adapt to different operational requirements while maintaining predictable behavior in each mode.
Data Source
AI summary
Network apparatus includes a plurality of interfaces, which are coupled to a network so as to receive and transmit data packets having respective link-layer headers and network-layer headers. Each link-layer header includes respective source and destination link-layer addresses and a link-layer priority value. Switching and routing logic is configured, responsively to the network-layer headers, to transfer each data packet from a respective ingress interface to a respective egress interface and to modify the source and destination link-layer addresses of the transferred data packet while copying the link-layer priority value from the ingress interface to the egress interface without modification.