Stateful Failover for Network Address Translation Devices

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Solution Overview

Problem

Network address translation (NAT) devices experience downtime and lost traffic during failovers due to inability to perform address translation and forward traffic, affecting redundancy and transparency in network operations.

Innovation Solution

Implementing 'stateful failover' redundancy support through synchronized session ownership between master and backup NAT devices using Virtual Router Redundancy Protocol (VRRP)-Extended (VRRP-e), ensuring continuous session management and traffic forwarding without dropping existing connections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a backup NAT device is configured for redundancy, then network reliability is improved, but downtime and lost traffic occur during failover

Engineering Contradiction:

Improvenetwork reliabilityVSAvoiddowntime during failover

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The backup NAT device performs preliminary actions by synchronizing session information and maintaining IP address ownership in advance. Session tables are replicated and validated before actual failover is needed, so when failure occurs, the backup device can immediately assume ownership and continue sessions without interruption.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent ensures continuity of useful action by maintaining active IP address ownership on the backup device and continuously synchronizing session state. This allows the backup device to seamlessly take over active sessions without breaking existing connections, eliminating downtime during failover events.

Inventive Principle:

Principle #20Continuity of useful action

2Reliability

If session information is synchronized between NAT devices, then failover continuity is improved, but device complexity increases

Engineering Contradiction:

Improvefailover continuityVSAvoidredundancy mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The backup NAT device creates a copy of the session information and IP address ownership state from the master device. This copying mechanism allows the backup device to replicate necessary state data without requiring complex real-time synchronization protocols, simplifying the overall redundancy architecture while maintaining failover continuity.

Inventive Principle:

Principle #26Copying

3Productivity

If IP address ownership is transferred during failover, then traffic forwarding is maintained, but connection state management becomes complex

Engineering Contradiction:

Improvetraffic forwarding continuityVSAvoidconnection state management

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent extracts IP address ownership from the master NAT device and transfers it to the backup device during failover. By extracting and relocating ownership of active IP addresses, the system maintains traffic forwarding continuity without requiring complex connection state management, as the backup device simply assumes the extracted ownership and continues sessions.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS7647427B1Redundancy support for network address translation (NAT)

Publication Date: 2010.01.12 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Stateful failover redundancy support is provided for network address translation (NAT). A master NAT device is backed-up with at least one back-up NAT device. Existing sessions are synchronized between the two NAT devices, such as via a dedicated link between them. In the event of a failover where the master NAT device is unable to perform its NAT functions, ownership of Internet protocol (IP) addresses is transferred from the master NAT device to the back-up NAT device. The back-up NAT device, which is now owner of the IP addresses, assumes the NAT functionality associated with these IP addresses and continues the existing sessions, as well as processing new sessions.