Tunnel-Side Packet Routing to Prevent ECMP Forwarding Loops

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Solution Overview

Problem

Equal-cost multi-path (ECMP) routing in tunnel networks can cause forwarding loops between remote and local ends due to hash-based load balancing, leading to transmission path errors and reduced network robustness.

Innovation Solution

Implement a routing forwarding method that determines the input direction of packets and sets their egress to a local egress when entering from a tunnel side, using access control lists and hash factors to ensure packets are forwarded only to local egresses, thereby avoiding loops and improving network robustness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If hash-based load balancing is used for ECMP routing, then routing efficiency and resource utilization are improved, but forwarding loops between remote and local ends occur

Engineering Contradiction:

Improverouting efficiencyVSAvoidforwarding loop prevention

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-establishing redirection rules in the access control list before packets arrive. When a packet enters from the tunnel interface, the system has already configured the ACL to redirect such packets to local egress interfaces, preventing the forwarding loop before it can occur. This proactive configuration ensures that ECMP routing maintains both efficiency and reliability.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If remote tunnel egress is selected by hash algorithm, then load balancing is achieved, but packets are forwarded back to local end causing loops

Engineering Contradiction:

Improveload balancing capabilityVSAvoidforwarding loop

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by making the egress selection dependent on the packet's entry interface. Packets entering from the access side can be forwarded to either local or tunnel egress based on load balancing, while packets entering from the tunnel side are specifically redirected to local egress only. This localized differentiation in forwarding behavior eliminates the harmful loop while preserving load balancing where applicable.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The access control list acts as an intermediary mechanism between the tunnel interface and the routing decision. The ACL rules intercept packets arriving from the tunnel interface and redirect them to local egress before the standard ECMP hash-based routing can select a tunnel egress. This intermediary layer prevents the forwarding loop without affecting the load balancing capability for other traffic flows.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If access control list redirection is used for tunnel packets, then forwarding loops are eliminated, but routing flexibility is reduced

Engineering Contradiction:

Improveloop eliminationVSAvoidrouting flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies partial action by applying the access control list redirection rule only to packets entering from the tunnel interface, while leaving packets from the access side to be routed using the full ECMP flexibility. The ACL rules are configured to match only specific tunnel interface packets, thereby eliminating loops for those packets without restricting the routing options for other traffic types and sources.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS20250293970A1Routing forwarding method, electronic device and storage medium

Publication Date: 2025.09.18 ZTE CORP

AI summary

Provided are a routing forwarding method, an electronic device, and a storage medium. The method includes determining an input direction of a packet and in response to determining that the input direction is a tunnel side, setting an egress of the packet to a local egress.