Passive Interface Designation for MPLS Peering Link Bandwidth Accounting
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Solution Overview
Problem
Current traffic engineering methods in computer networks, particularly when using Multi-protocol Label Switching (MPLS), fail to account for constraint information of peering links, leading to congestion and suboptimal path selection due to lack of bandwidth availability data for links outside the network.
Innovation Solution
Designating peering links as 'passive interfaces' within the network, allowing for the collection and advertisement of bandwidth availability information, which is then used by interior routing protocols to compute paths that avoid congested links, even if the links do not support resource reservation protocols like RSVP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the interior routing protocol selects the shortest path to exit points, then path selection speed is improved, but congestion occurs on peering links because constraint information for external links is unavailable
Solution Approach 1:
The patent applies preliminary action by having border routers pre-calculate and advertise constraint information (bandwidth availability, latency, etc.) for peering links to interior routing protocols before path selection occurs. This allows interior protocols to compute constrained shortest paths that avoid congested peering links while maintaining efficient routing, thus resolving the contradiction between fast path selection and reliable bandwidth availability.
2Loss of information
If peering links are designated as passive interfaces, then constraint information can be collected and advertised, but the interfaces cannot support resource reservation protocols like RSVP
Solution Approach 1:
The patent applies segmentation by dividing the network into interior and exterior segments, where passive interface designation separates the functions of constraint information collection (interior) from resource reservation (exterior). Border routers act as transition points that collect constraint information from peering links and advertise it internally without requiring RSVP support on the peering interfaces themselves, thus resolving the contradiction between information availability and protocol support.
3Adaptability or versatility
If multiple exit points are available, then path diversity is improved, but suboptimal path selection occurs when peering link congestion is unknown
Solution Approach 1:
The patent applies feedback by implementing a mechanism where border routers continuously monitor peering link constraint information (bandwidth availability, utilization) and dynamically advertise updated constraints to interior routing protocols. This feedback loop enables the routing protocol to select optimal exit points based on current peering link conditions, resolving the contradiction between path diversity and traffic engineering effectiveness by ensuring diverse paths are selected based on real-time link status.
Data Source
AI summary
Constraint information associated with peering links is taken into account when establishing label switched paths (LSPs) to exit points of a network. Devices within the network, such as routers, designate interfaces associated with peering links as “passive interfaces” to indicate that the interfaces should be included for bandwidth accounting purposes and internal path computation. Other devices within the network utilize the constraint information, e.g., bandwidth availability, when computing and establishing LSPs to the exit points of the network to avoid congested peering links.