Designated Forwarder Selection Using Route Identifiers
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Solution Overview
Problem
In multihomed networks, the existing designated forwarder election algorithms can lead to layer 2 loops due to differences in VLAN identifiers and ESI configurations among provider edge devices, causing them to select different designated forwarders and result in redundant forwarding of broadcast, unknown unicast, and multicast traffic.
Innovation Solution
Provider edge devices exchange route identifiers that include VLAN identifiers and ESI configurations using TLV elements, allowing them to select a common designated forwarder using the V mod N algorithm, ensuring compatibility and preventing layer 2 loops by identifying a minimum common VLAN identifier or ESI configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing designated forwarder election algorithms are used in multihomed networks, then multiple links are provided for packet routing to increase reliability, but layer 2 loops occur due to different VLAN identifiers and ESI configurations causing different devices to select different designated forwarders
Solution Approach 1:
The patent changes the parameters used for designated forwarder selection from local device configurations (VLAN identifiers and ESI configurations) to a shared parameter (route identifier) that is consistent across all provider edge devices. This ensures that all devices select the same designated forwarder and prevents layer 2 loops while maintaining multihoming reliability
Solution Approach 2:
The patent creates equipotentiality by having all provider edge devices use the same route identifier (received from the same customer edge device) as the basis for selecting the designated forwarder. This equalizes the selection criterion across all devices, ensuring they arrive at the same designated forwarder despite having different local configurations
2Adaptability or versatility
If devices use different VLAN identifiers and ESI configurations for designated forwarder selection, then device configuration flexibility is maintained, but different designated forwarders are selected resulting in redundant traffic forwarding
Solution Approach 1:
The patent segments the designated forwarder selection process into two independent parts: (1) keeping local device configurations (VLAN identifiers and ESI configurations) for device-specific functionality and flexibility, and (2) using a separate shared route identifier for consistent designated forwarder selection across all devices. This segmentation allows both configuration flexibility and efficient traffic forwarding
Solution Approach 2:
The patent introduces a route identifier as an intermediary element that mediates between different device configurations. The route identifier, received from the customer edge device, serves as a common reference that all provider edge devices use to select the same designated forwarder, while local configurations remain unchanged for device-specific operations
Data Source
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AI summary
A device may receive a route identifier that includes a range identifier or a configuration identifier. The range identifier may identify a range of broadcast domain identifiers associated with a first device. The configuration identifier may identify an Ethernet segment identifier (ESI) configuration of the first device. The device may identify the range identifier or the configuration identifier included in the route identifier. The device may select a designated forwarder from among multiple devices based on the range of broadcast domain identifiers or based on identifying the configuration identifier. The designated forwarder may be the same designated forwarder selected by at least one other device.