SPB Anycast Gateway Selection for Lower-Latency Redundancy
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Solution Overview
Problem
Existing gateway redundancy protocols in SPB networks, such as VRRP and DVR, do not provide true anycast gateway functionality, leading to sub-optimal IP routed paths with higher latency and constraints, as they elect a single primary gateway despite other paths having lower costs, and require additional control plane messaging.
Innovation Solution
Implement anycast gateways for ISIS SPBM networks that leverage SPB's shortest path mechanism to select the nearest available gateway by using TLVs to validate and verify gateway configurations, allowing multiple gateways to actively forward traffic without additional control plane messaging, and utilize SPB's Link State Databases to propagate and validate anycast gateway configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple gateways are used for redundancy purposes in the SPB network, then gateway availability is improved, but one gateway becomes the primary gateway and the other gateways are not used, resulting in sub-optimal IP routed paths with higher latency
Solution Approach 1:
The patent merges the functions of multiple gateways by allowing them to all actively forward traffic for the same L2 segment and I-SID. Instead of having one primary and multiple standby gateways, all gateways participate in forwarding, with each gateway using its own unique BMAC address. This combining of gateway functions eliminates the single-point bottleneck and allows traffic to be distributed across multiple paths, reducing latency while maintaining redundancy.
Solution Approach 2:
The patent implements dynamic gateway selection where access nodes can dynamically choose the nearest gateway based on real-time path costs and availability. The system dynamically adapts to changing network conditions by allowing different access nodes to use different gateways, and by enabling gateways to dynamically assume the role of primary gateway for specific L2 segments or I-SIDs based on their proximity and operational status, rather than having a static primary gateway assignment.
2Reliability
If traditional gateway redundancy protocols are used, then gateway failover is achieved, but additional control plane messaging is required, increasing device complexity
Solution Approach 1:
The patent extracts the complex control plane messaging mechanisms from the gateway redundancy system. Instead of using protocols like VRRP that require extensive control plane communication for gateway election and status monitoring, the system leverages the existing SPB control plane (ISIS-SPB) that already provides comprehensive link-state information. The gateway redundancy functionality is achieved through data plane mechanisms and existing control plane data, eliminating the need for separate redundancy control protocols.
Solution Approach 2:
The patent makes the SPB control plane universal by having it serve multiple functions: it provides both the routing information needed for shortest path bridging and the gateway configuration information needed for redundancy. The ISIS-SPB protocol and its Link State Databases are used for both L2 routing and L3 gateway management, eliminating the need for dedicated redundancy protocols and reducing overall control plane complexity.
3Ease of operation
If a single primary gateway is elected, then gateway management is simplified, but the path cost to reach the primary gateway may be higher than other gateways, reducing network efficiency
Solution Approach 1:
The patent applies local quality by allowing different access nodes to have different primary gateways based on their local network position and proximity. Instead of having a single global primary gateway, each access node or L2 segment can have its own primary gateway selected based on the lowest path cost from that specific location. This localized gateway selection optimizes the path cost for each segment of the network while maintaining simple gateway management through automated selection based on ISIS-SPB path costs.
Data Source
AI summary
Disclosed herein are system, method, and computer program product aspects for implementing anycast gateways. Some aspects of this disclosure relate to a method including receiving, by an access node, a first TLV from a first gateway. The first TLV includes a CMAC address for the first gateway, an IP address of the first gateway, and an L2 I-SID associated with the first gateway. The method further includes receiving, by the access node, a second TLV from a second gateway, where the second TLV includes the CMAC address, the IP address, and the L2 I-SID. The method further includes, in response to determining that the L2 I-SID exists in an LSDB of the access node, determining that the first gateway is closer to the access node than the second gateway. The method also includes storing the CMAC address in a database to point to the first gateway based on the determination.