In-Service Software Upgrade with Active Monitoring
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Solution Overview
Problem
Conventional in-service software upgrade (ISSU) processes for network devices often require service shutdowns and are not suitable for resource-constrained devices, as they cannot react to external or internal events during the upgrade, leading to potential network outages and instability.
Innovation Solution
The proposed ISSU solution detaches the control plane from the data-plane management to allow continuous service provision during software upgrades, using a temporary ISSU database to maintain the pre-upgrade data-plane configuration, and actively monitors critical services to detect and respond to events that may affect network stability, enabling separate upgrades of data-plane-management and control-plane software without interrupting services.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ISSU processes are used to upgrade network device software, then the software version is updated, but service shutdowns occur and network outages may result
Solution Approach 1:
The system segments the software upgrade process into two independent phases: first upgrading the data-plane-management function while the control plane remains operational, then upgrading the control-plane function. This segmentation allows continuous service provision during upgrade, resolving the contradiction between maintaining network continuity and achieving upgrade capability.
Solution Approach 2:
The system generates an ISSU database containing a copy of the data-plane state before upgrading begins. This preliminary action preserves the pre-upgrade configuration, allowing the system to recover if needed and enabling the upgrade process to proceed without interrupting services, thus maintaining network continuity while enabling upgrades.
2Reliability
If service monitoring is not implemented during ISSU, then the upgrade process is simpler, but network outages cannot be prevented
Solution Approach 1:
The system implements active monitoring of critical services during the ISSU process, continuously feedbacking on service health status. When degradation or failure is detected, the system responds by aborting the upgrade or rolling back changes. This feedback mechanism maintains network stability while managing the complexity of the upgrade process.
Solution Approach 2:
The system prepares remedial actions in advance, including the ISSU database with pre-upgrade state and monitoring thresholds for critical services. This beforehand cushioning enables the system to prevent network outages by having recovery mechanisms ready before issues occur, balancing reliability improvement with controlled complexity.
Data Source
AI summary
A system for performing in-service software upgrade on a network device is provided. In response to a software-upgrade command, the system generates an upgrade database based on a state database storing both a data-plane state and a control-plane state associated with the network device. The network device is managed by a management unit comprising a data-plane-management sub-unit and a control-plane sub-unit, and the upgrade database stores at least the data-plane state to allow the data-plane-management sub-unit to operate based on the upgrade database. The system separately upgrades the data-plane-management sub-unit and the control-plane sub-unit, without interrupting services provided by the network device. The system monitors the state database and the upgrade database to detect an event associated with the network device. In response to determining a triggering condition being met, the system performs an action to prevent a network outage or error.