Asymmetric Redundancy for Multi-Homed Network Access Topologies
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Solution Overview
Problem
Existing redundancy mechanisms in multi-homed network access topologies, such as all-active and single-active redundancy, fail to reliably enforce quality-of-service (QoS) policies and can result in duplicate packets or permanent traffic drop due to load-balancing and gateway protocol interactions.
Innovation Solution
An asymmetric redundancy scheme is implemented, using anycast addressing on the access network side and designated forwarder (DF) election on the core network side, with split-horizon filtering to prevent looping and ensure efficient QoS enforcement, allowing multiple PEs in a redundancy group to be active for incoming traffic and a single PE to be active for outgoing traffic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all-active redundancy is used, then network resilience is improved, but duplicate packets and QoS policy enforcement failures occur
Solution Approach 1:
The patent applies asymmetry by implementing different redundancy behaviors for incoming and outgoing traffic directions. In the incoming direction, all PEs remain active for resilience, while in the outgoing direction, only the designated forwarder is active to prevent duplicate packets. This directional asymmetry resolves the contradiction between maintaining network resilience and preventing duplicate packet transmission.
2Productivity
If load-balancing is implemented, then traffic distribution is improved, but QoS policy enforcement becomes unreliable
Solution Approach 1:
The patent segments the redundancy group into two functional roles: the designated forwarder responsible for QoS policy enforcement and outgoing traffic, and other PEs responsible for incoming traffic and backup functions. This segmentation allows load-balancing to distribute incoming traffic while ensuring that only the designated forwarder handles outgoing traffic, thereby maintaining reliable QoS policy enforcement.
3Adaptability or versatility
If gateway protocol interactions are used, then routing flexibility is improved, but permanent traffic drop occurs
Solution Approach 1:
The patent introduces the designated forwarder as an intermediary between the gateway protocol interactions and the actual traffic forwarding. The designated forwarder receives routing information from gateway protocols and uses this information to make intelligent forwarding decisions, preventing permanent traffic drop while maintaining routing flexibility. Other PEs in the redundancy group follow the designated forwarder's decisions, ensuring consistent traffic delivery.
Data Source
AI summary
In one embodiment, a method is described. The method includes receiving a network communication at a first network device coupled to a first network and a second network, determining whether to forward the network communication into the first network over a logical connection, and, if the network communication is to be forwarded into the first network over the logical connection, forwarding the network communication into the first network over the logical connection. The network communication comprises a first network address in the second network that is associated with a second network device coupled to the second network. The logical connection is associated with a second network address in the second network. The determining is based, at least in part, on a determination, as to whether the first network device and the second network device are coupled to the logical connection, that uses the first network address and the second network address.