Edge Router Refresh Signaling for QoS State Restoration
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Solution Overview
Problem
Current resource reservation protocols in IP networks face challenges in managing state information during re-routing events, leading to potential severe congestion and unmet Quality of Service (QoS) requirements, especially when re-routing across multiple Autonomous Systems (AS) without maintaining per-flow states in interior nodes.
Innovation Solution
A mechanism is introduced that uses an edge-router-refresh message to restore state information related to QoS for data flows following re-routing events, involving a new upcall interface between the routing engine and resource management module to notify of inter-AS route changes, and sending a new signalling message from the ingress router to build necessary states in egress routers on the modified path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If per-flow reservation states are stored in each router along the path, then QoS can be ensured for individual flows, but the device complexity and memory requirements increase significantly in large networks with high number of flows
Solution Approach 1:
The patent segments the network into stateful edge routers and stateless interior routers. Only edge routers maintain per-flow reservation states, while interior routers process packets based on aggregated flow states. This segmentation reduces the overall device complexity by distributing state management responsibilities strategically throughout the network hierarchy.
Solution Approach 2:
The patent introduces a new dimension to state management by implementing soft states with timeout mechanisms and periodic refresh operations. Instead of maintaining permanent states, the system uses temporal dimension (time-based validity) to manage reservation states, allowing automatic state expiration and reduction of state table sizes in edge routers.
2Reliability
If RSVP refresh messages are sent periodically to maintain reservation states, then QoS reservations are maintained, but network overhead increases and congestion may occur during re-routing events
Solution Approach 1:
The patent implements periodic refresh messages that are sent at intervals to maintain soft reservation states. These periodic actions keep reservations alive without requiring continuous messaging, reducing overall network overhead while ensuring QoS guarantees are maintained throughout the reservation period.
Solution Approach 2:
The patent sends refresh messages in advance before reservation timeouts occur, and implements proactive state restoration mechanisms that detect re-routing events and send restoration messages before congestion can develop. This preliminary action prevents rather than reacts to problems.
3Device complexity
If interior routers are made stateless to improve scalability, then device complexity is reduced, but the ability to handle re-routing events and maintain QoS is weakened
Solution Approach 1:
The patent introduces edge routers as intermediary nodes that maintain per-flow states and coordinate re-routing operations. These edge routers act as mediators between the control plane (routing protocols) and data plane (packet forwarding), enabling interior routers to remain stateless while still supporting QoS and re-routing through the intermediary edge router layer.
Solution Approach 2:
The patent implements feedback mechanisms where edge routers monitor reservation state validity and send refresh or restoration messages based on detected conditions. The system uses feedback from routing event detection to trigger appropriate state management actions, ensuring QoS is maintained even with stateless interior routers.
4Adaptability or versatility
If re-routing occurs across multiple Autonomous Systems without state synchronization, then routing flexibility is improved, but congestion occurs due to lost reservation states at edge routers
Solution Approach 1:
The patent implements a universal edge router refresh message format that can be used across multiple Autonomous Systems and different routing scenarios. This single message type serves multiple functions: initial reservation, state refresh, and state restoration after re-routing, providing multi-functionality that maintains QoS across diverse inter-AS routing environments.
Solution Approach 2:
The patent sends edge router refresh messages proactively after detecting re-routing events, before congestion can occur. The system anticipates potential state loss at edge routers and restores states in advance, maintaining QoS continuity across AS boundaries without waiting for congestion to manifest.
Data Source
AI summary
Methods, edge routers and an edge-router-refresh network signalling message used to update state information in edge routers. A data session is established on a path from a source towards a destination connected from the source via a plurality of Autonomous Systems (AS). The edge-router-refresh network signalling message is created by an edge router acting an an ingress edge router. The edge-router-refresh network signalling message comprises an identifier of the data session, an identifier of the edge router, which issued the edge-router-refresh message and an indication that the edge-router-refresh message is meant to be used by the edge routers present on the modified path. Optionally, the edge-router-refresh network signalling message further comprises a list of the plurality of AS traversed by the path before the modification.