Core Router ASBR Failure Protection via Protector Router
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Solution Overview
Problem
Current Fast Reroute technologies in IP/MPLS networks are inadequate for protecting border routers (ASBR) in large-scale networks, as they either require excessive resource allocation or fail to provide deterministic rerouting within the necessary time frame for high-availability services like VoIP and telemedicine, which demand rerouting in under 100 milliseconds.
Innovation Solution
Implementing a core router with means to identify and redirect traffic through a back-up output router or protector router, bypassing the nominal output router in case of failure, using pre-installed correspondence tables and contextual routing tables that do not pass through the nominal output router, ensuring deterministic rerouting within 100 milliseconds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MPLS Fast Reroute mode with meshing of border routers is used, then protection against ASBR failures is achieved, but the number of tunnels required becomes proportional to the square of the number of ASBR, making it inapplicable to large-scale networks
Solution Approach 1:
The invention segments the protection mechanism by introducing a dedicated protector router that handles all backup routing functions centrally. Instead of meshing all ASBRs with multiple tunnels, the system divides the protection function into: (1) primary ASBRs handling normal traffic, (2) a dedicated protector router handling backup routing, and (3) back-up output routers providing alternative paths. This segmentation reduces the tunnel requirement from O(n²) to O(n) where n is the number of ASBRs.
Solution Approach 2:
The protector router acts as an intermediary between core routers and back-up output routers. It receives traffic from core routers that would normally go to ASBRs, performs route calculation when failures occur, and forwards traffic through appropriate back-up paths. This intermediary eliminates the need for direct tunnel connections between all pairs of ASBRs, significantly reducing overall network complexity.
2Reliability
If Fast Reroute technology is implemented to achieve deterministic rerouting in under 100 milliseconds, then high availability for real-time services is ensured, but the technology cannot protect ASBR in large-scale networks due to resource constraints
Solution Approach 1:
The protector router implements self-service by maintaining pre-calculated backup routes and automatically performing route calculations when failures occur. It monitors the status of ASBRs and back-up paths, and autonomously switches traffic without requiring external intervention or complex coordination across the entire network. This self-service capability enables fast rerouting while keeping resource requirements manageable.
Solution Approach 2:
The system performs preliminary actions by pre-establishing backup routes and pre-configuring the protector router with alternative paths before failures occur. The protector router maintains a pool of pre-calculated routes to back-up output routers, so when an ASBR fails, traffic can be immediately redirected without waiting for route computation. This preliminary preparation ensures sub-100-millisecond rerouting while enabling scalability.
3Reliability
If present-day Fast Reroute techniques using only IGP information are used, then internal network failures are protected, but ASBR failures cannot be protected as external routing information from BGP is not considered
Solution Approach 1:
The invention merges IGP and BGP routing information processing within the protector router. It simultaneously considers internal network topology (from IGP) and external routing information (from BGP sessions with ASBRs) to compute comprehensive backup paths. This combination allows the protector router to understand both internal network constraints and external destination requirements, enabling it to provide backup routes for ASBR failures that maintain connectivity to external networks.
Solution Approach 2:
The protector router is designed with multi-functionality, serving both as an IGP router (handling internal routing) and a BGP speaker (handling external routing information). It performs multiple functions: monitoring ASBR status, calculating backup routes using both IGP and BGP information, and forwarding traffic through appropriate paths. This universal design enables protection against both internal and ASBR failures within a single router.
Data Source
AI summary
A core router adapted to back up a nominal output router. This kind of core router of a first autonomous subsystem is connected to a nominal output router of the first autonomous system adapted to route traffic whose destination is a second autonomous system, the first autonomous system further including a back-up output router adapted to route traffic whose destination is the second autonomous system. The core router includes means for identifying a router of the first autonomous system, adapted to identify a router adapted to route traffic whose destination is the second autonomous system in the event of a failure affecting traffic to said nominal output router, the identified router being either the back-up output router or a protector router of the first autonomous system, this protector router being adapted to redirect traffic whose destination is the second autonomous system via said back-up output router; means for detecting a failure affecting routing of traffic to said nominal output router; and means for redirecting traffic whose destination is the second autonomous system in a predetermined route in a tunnel to the identified router, said tunnel not passing through the nominal output router.