Inter-Domain Multi-Path Routing with Loop-Free AS Path Ordering
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Solution Overview
Problem
Existing Border Gateway Protocol (BGP) is prone to non-termination and route oscillation issues, leading to instability and loop formation when routing across Autonomous Systems (ASes), with existing solutions failing to provide stable, loop-free multi-path routing.
Innovation Solution
The Ordered Path Etiquette for Routing Algebra (OPERA) is introduced, which modifies the policy mechanisms of BGP to ensure stable, loop-free routing across ASes by enforcing a routing etiquette through the Ordered Border Gateway Protocol (OBGP), using label-induced order relations to maintain loop-free paths and ensure convergence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If BGP is used for inter-domain routing across Autonomous Systems, then routing flexibility and policy control are improved, but route stability and loop-free guarantee deteriorate due to non-termination and route oscillation issues
Solution Approach 1:
The patent applies preliminary action by embedding an ordered list of Autonomous System identifiers in routing control packets before transmission. This ordered list serves as a pre-established constraint that prevents loops before they can form, eliminating the need for reactive loop detection and resolution mechanisms in traditional BGP.
Solution Approach 2:
The patent introduces an intermediary mechanism (the ordered AS list) that mediates between routing flexibility and loop prevention. This intermediary structure enables routers to make autonomous decisions about route validity based on the embedded ordering information, without requiring complex inter-router coordination or global policy agreement.
2Adaptability or versatility
If traditional BGP routing protocols are used, then multi-path routing capability is provided, but convergence stability deteriorates due to route oscillation and non-termination
Solution Approach 1:
The ordered AS list is embedded in routing control packets before transmission, establishing a pre-condition for loop-free routing. This preliminary structuring of routing information enables stable convergence by preventing the formation of routing loops that cause oscillation, while still allowing multiple valid paths to coexist.
Solution Approach 2:
The patent changes the parameter structure of routing information by introducing an ordered sequence of AS identifiers rather than using traditional distance-vector or path-vector metrics. This parameter transformation fundamentally alters how routes are evaluated and selected, enabling stable multi-path routing without oscillation.
3Reliability
If loop detection mechanisms are added to BGP, then route stability is improved, but protocol complexity and overhead increase
Solution Approach 1:
The patent extracts the loop detection function from complex runtime mechanisms and embeds it directly into the routing control packet structure itself. By taking out the loop prevention logic and encoding it in the ordered AS list within packets, the system achieves loop-free routing without adding complex detection algorithms or increasing protocol state machine complexity.
Solution Approach 2:
The routing control packets become self-service by containing within themselves the information needed to validate loop-free paths. Each router can independently validate routes using the embedded ordered AS list without requiring external loop detection mechanisms, coordination with other routers, or complex inter-router signaling.
Data Source
AI summary
Techniques for routing in communications networks include receiving, at a first border node in a first autonomous system (AS) from a neighbor node in a second AS, a first routing control packet for a route to a destination node. The packet indicates a first ordered list of ASes involved in the route in an order each AS is traversed along the route. If the first ordered list does not include the first AS then a loop free route to the destination node is accepted by storing a route that indicates an updated ordered list that includes the ordered list and also indicates the second AS. A second routing control packet that indicates the destination node and the updated ordered list is sent to neighbors.